Many materials like fabrics, plastic foils, and papers are processed on the fly using a reel to reel process. Applications may be found in the medical and food industry in the manufacturing of pouches for soups, coffee or beverages, but also in digital printing lines or production lines for grinding paper. Lasers are an established tool in these converting lines. Typical applications are cutting (incl. kiss cutting), scoring and drilling. In one example, the material is processed in the direction of travel or in a down web application. In this case, the laser beam is focused on the web by a fixed optic, while the material is moved underneath by web, allowing the material to be slit to width. In another example, the material is processed perpendicular to the material (web) flow direction. This is referred to as a cross web application. A galvanometric scanner steers the laser beam across the material while compensating for the material flow speed by using a velocity sensor. In most cases, a CO2 laser is used emitting a wavelength of 10.6 µm or 10.2 µm (ideal for PP processing), as mainly organic materials and plastics are processed. This wavelength is absorbed with most of the materials very well. In some special instances such as in the medical segment, UV lasers are used.
In flexible display manufacturing, transistors fabricated on a thin polymer/glass substrate must be detached from the substrate to yield a flexible polymer display. Laser-based lift-off eliminates the use of less selective mechanical or chemical processes, and leverages infrastructure already in place that previously handled rigid substrates. Thus, it is not only friendly at a material level, it is environmentally and cost-effective. Excimer lasers deliver the necessary pulse energy to be highly selective, and to process large areas at industrial speed and with superior quality and yield.
The challenge for Liquid crystal display (LCD) manufacturers is to produce higher performance displays, while simultaneously reducing cost and increasing display size. Excimer line beam annealing of low-temperature polycrystalline silicon thin-film transistor (LTPS-TFT) technology enables both lower cost and higher display performance through lower process temperatures (allowing for thinner substrates) and the superior electron mobility of polycrystalline silicon over amorphous silicon. The basic principle of excimer laser annealing is quite simple in concept, but anything but so in implementation: The excimer laser beam is homogenized and shaped to a line and scanned across the Silicon. Each laser pulse melts an incremental amount of the amorphous silicon. Polycrystalline structure occurs upon recrystallization.
Coherent’s Laser Cutting Tools are ideal for cutting perfect parts from all types of materials from metals, plastics, and composites to paper, ceramics and wood.
From tactical weapon systems and smart munitions to harsh flight-qualified hardware, Coherent is your partner for next-generation, high-power diode lasers and systems.
Coherent is uniquely positioned to meet your most demanding high-power visible (650 nm to 690 nm) and near-infrared (770 nm to 980 nm) diode laser component and laser weapon system requirements.
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Pump-probe experiments using picosecond or femtosecond lasers.
Generally, ultrafast spectroscopy refers to pump-probe experiments using picosecond or femtosecond lasers to get time-resolved spectral information.
Traditionally ultrafast spectroscopy was restricted to gas phase reactions, where molecules are considered to be isolated. It is therefore easier to distinguish spectral features and energy transfer mechanisms than in condensed phase systems. These experiments have lead to an ever increasing knowledge of gas phase reactions resulting in quantum control of reactions in the gas phase.
Since the development of reliable solid-state ultrafast lasers over 10 years ago, ultrafast spectroscopy is not limited to gas phase reactions. The ability to choose pulsewidth, wavelength, or amplify the traditional Ti:S output means ever more increasing applications in condensed phase systems as well.
Ultra short FIR pulses as a spectroscopic tool.
There are numerous processes that occur in the far-infrared (FIR) region of the spectrum that have not been studied directly due to the lack of availability of ultrashort FIR pulses. Recent developments have yielded ultrashort FIR pulses, referred to as THz pulses (0.1 to about 6 THz), and the full capability of this technique is just starting to take off. Techniques once limited to the UV, visible and IR region can now begin to be applied to the FIR region as well. Attention has been focused on generating these THz pulses and understanding the physics of generation and propagation; now the actual THz pulses can be used as a spectroscopic tool.
THz spectroscopy has applications in semiconductors, liquids, gases and 2-D imaging. Imaging is rapidly emerging as an exciting THz application, and images can be taken using transmission or reflection geometry. By analyzing the THz waveform in either the time domain (material homogeneity or thickness variations) or the frequency domain (frequency-dependent absorption) as well as by other methods, images identifying material properties can be constructed (J.V. Rudd, D. Zimdars, and M. Warmuth, Picometrix, Inc., “Compact, fiber-pigtailed, terahertz imaging system”). Polar liquids and gases are highly absorptive in the THz regime; therefore, these type of samples are readily suitable for THz imaging. Such imaging serves as a complement to existing imaging methods or allows substances that haven’t been studied previously to be imaged. Recent examples of published THz imaging applications include: identifying raisins in a box of cereal by water content; studying water uptake and evaporation in leaves; examining circuit interconnects in packaged ICs; reading text in envelopes or beneath paint; identifying tooth decay; locating water marks in currency (also from J.V. Rudd et al, “Compact, fiber-pigtailed, terahertz imaging system”).
The number of commercially available terahertz imaging systems is extremely few even though many applications are emerging for THz imaging. New techniques have been developed for the generation and detection of THz radiation based on frequency conversion using nonlinear optics. THz techniques combine pulsed ultrafast laser technology with optoelectronics to generate terahertz radiation with sub-picosecond pulse duration. A typical set-up includes a modelocked solid-state laser that produces pulses with 100 femtosecond pulsewidths. The Coherent Vitara laser can be used as the femtosecond optical excitation source; alternatively, the Mira Optima 900-F system may be used. The Vitara offers the advantage of using a hands-off, turnkey solution in a single, compact, rugged package that includes the Verdi diode-pumped solid-state pump laser operating at 532 nm and the modelocked Ti:S oscillator.
Low noise lasers enable interferometry with unprecedented precision.
Low noise laser systems allow the detection of very small length changes with a precision that was unattainable until just recently. High precision interferometry now enables the study of previously unobserved phenomena such as gravitational waves. The direct detection of gravitational waves stands at the beginning of a whole new field of astronomy, because such waves are emitted by very massive accelerated objects such as black holes, which are often not visible with conventional telescopes. For this purpose, large scale Michelson interferometers housed within vacuum systems with an arm length of several kilometers are being built at several sites around the world. A passing gravitational wave will cause a very small arm length change in such an interferometer. Great care has to be taken to suppress all other potential noise sources below the strength of the signal that is to be detected. Such unwanted noise sources are seismic noise, thermal noise, electronic noise , as well as noise associated with the laser. Multiple stage monolithic suspensions of the interferometer optics and advanced interferometer designs with arm cavities and additional power and signal recycling mirrors are being used to address these noise sources. The laser of choice in these high precision interferometers is usually the Mephisto laser due to its very low frequency noise.
In related experiments, fundamental quantum optic effects and the generation and application of squeezed light are studied. The observation of these effects is only possible when an ultra stable low noise laser system is available.
When a higher output power is needed, the Mephisto MOPA is available with the same frequency stability. Interferometry applications at different wavelength such as 1319 nm or 532 nm are also possible.
Instead of detecting changes in the arm length of an interferometer, some standard institutes and research facilities require the measurement of an absolute length with very high precision. To achieve this, an absolute frequency standard, as well as extremely low frequency noise are required. The iodine stabilized Prometheus laser fulfills these requirements.
This type of spectroscopy analyzes fluorescence as a function of wavelength when the laser is tuned to an electronic absorption of the sample.
This type of spectroscopy analyzes fluorescence as a function of wavelength when the laser is tuned to an electronic absorption of the sample. In general, luminescence involves the emission of electromagnetic radiation by a material after that material has absorbed energy from a light source. Luminescence is described as fluorescence when the time lag between excitation and emission is on the order of 10 nanoseconds. Laser-induced fluorescence (LIF) can be used for a wide array of applications, including the qualitative and quantitative measurements of the concentrations of molecules in a sample and the mapping of energy level diagrams.
Fluorescence studies are usually conducted with tunable continuous wave (cw) laser systems; the use of frequency-doubled Ti:Sapphire (Ti:S) lasers enhance the experimental capabilities of cw fluorescence measurements. For broadband fluorescence studies of samples in the solid or liquid states, linewidths between 2 and 400 GHz are usually suitable.
For fluorescence spectroscopic experiments in the gas phase, the most important laser parameter may be the linewidth. For reliable high-resolution fluorescence studies, which dictate linewidths under 10 MHz and high output power, Coherent’s Ring Laser is designed for optimum performance with Ti:S gain media (Ti:dye). Systems such as the MBR-110 ring lasers operate reliably over extended periods of time with linewidths as low as 75 kHz.
One of the most important contributions to fluorescence spectroscopy has been the availability of ultrafast lasers capable of picosecond and femtosecond pulses in time-resolved fluorescence measurements. Lasers such as the Mira Optima 900 have allowed direct excitation of materials within the lifetime of an excited state.
Narrow linewidth lasers with broad tuning range enable advances in high resolution spectroscopy.
Laser-based atomic spectroscopy is the measurement of absorption, emission, or scattering of electromagnetic radiation by atoms and molecules (or atomic and molecular ions) to study these species and their related physical processes. The interaction of radiation with matter causes redirection of the radiation and/or transitions between the energy levels of atoms and molecules. There are three types of events that are often studied with lasers: absorption, fluorescence and scattering.
Absorption happens when photons are absorbed by the atom and its electrons are promoted to higher energy levels. Absorption can be studied measuring the amount of laser light transmitted by the sample as a function of the wavelength. Fluorescence happens when the excited electron decays back to its original state by emitting a photon of light at a longer wavelength (smaller energy) than the exciting photon from the laser. Scattering may be elastic (like Rayleigh and Mie scattering) or inelastic. Inelastic scattering takes places in atoms, molecules or lattices where part of the photon energy is transferred to/from the medium in processes like Raman or Brillouin scattering. In this section we consider mostly absorption and fluorescence spectroscopy and steady-state phenomena with high spectral resolution, rather than time-resolved studies, where pico- or femtosecond pulses are used. For a description of Raman scattering applications, please go to the section “Raman Spectroscopy”.
There are many high-resolution spectroscopic techniques. For example, the laser wavelength can be tuned to an electronic absorption of the sample and the resulting fluorescence can be analyzed as a function of wavelength. Alternatively, if laser excitation at an initial wavelength is introduced to a sample, absorption/transmission spectroscopy can be used to monitor the amount of light transmitted through the sample. If the excitation wavelength is scanned, an absorption spectrum can be analyzed. Many distinctions of this spectroscopy exist.
Lasers play an important role in high-resolution spectroscopy because of their simultaneous high-power output beam and narrow linewidth. Atomic spectroscopy (both absorption and fluorescence) usually requires wavelengths between 100 nm and 2 micron. Tunable Titanium Sapphire lasers are ideally suited for atomic spectroscopy because they provide powers and tuning ranges unavailable with any other source. The natural tuning range of 700-1,000 nm can be extended using second harmonic generation to cover the region 350-500 nm. Coherent’s MBR family of CW tunable lasers offer all these wavelength ranges with different power levels and with various linewidths. The flagship model MBR-110 provides a very narrow 75 kHz linewidth, suitable for high-resolution studies. The laser output of the MBR lasers can be stabilized and scanned to provide accurate spectra of atomic species. The MBD-200 resonant ring frequency-doubler efficiently converts the MBR output to its second harmonic and further extends the available wavelength range.
Coherent’s Ion lasers (Innova 300 series) can be operated in single frequency at several blue and green wavelengths and provide linewidths narrower than 50 MHz. The single frequency Verdi DPSS laser produces up to 18 Watts at 532 nm and 20 W at 1064 nm. The specifically designed doubler MBD-266 can be used to convert the green output of Verdi to its second harmonic in the deep UV.
The development of methods to cool and trap atoms using laser light.
The control of atomic motion by laser light is an application that has exploded over the last few years. The possibility of reaching extremely low atomic kinetic-energy temperatures near absolute zero is perhaps the most astonishing achievement. Research in atom trapping and cooling has led to insights into the interaction of matter and radiation and a variety of applications in areas such as spectroscopy, atomic clocks, atomic interferometers, optics, lithography, and gravitational measurements.
Laser beams are used to chill atoms and trap them in space. At first it would seem that cooling atoms using a laser source would be unlikely, but the technique has readily been demonstrated by the Nobel prize-winning work of Steven Chu, William D. Phillips and Claude Cohen-Tannoudji. When an atom is illuminated by counter-propagating light and absorbs a photon, its momentum changes the atomic velocity. After many cycles of absorption and emission, the velocity of the atom becomes nearly zero. In each cycle the atom loses energy which corresponds to the Doppler shift. The kinetic energy of the atom can eventually be lower than one microKelvin. This atom can then be trapped by two opposing laser beams that have frequencies lower than the atom’s absorption maximum. As the atom moves in the direction of one of the laser beams it sees a frequency increase (Doppler effect). The frequency increase moves into the atom’s absorption band causing a momentum kick in the opposite direction. The atom is then fixed in space by the two beams. Cooling allows the atom to be held longer since its random thermal motions are minimized.
Laser cooling applications demand single-frequency operation in the visible (red) and IR wavelength region. Sodium, rubidium and cesium are the most common atoms used in cooling experiments, Coherent’s MBR-110 Monolithic Block Resonator is well suited to the study of these atoms.
Solid-state lasers are used in a wide variety of applications, ranging from materials processing to entertainment to medical treatment. Optical pump sources for solid-state lasers have traditionally been lamp-based. However, because flashlamps emit light that is distributed over a significantly wider spectrum than most solid-state gain media, much of the energy from the pump light is wasted as heat into the system. Moreover, flashlamps must be considered as consumables, because their typical lifetimes are only hundreds of hours.
Recently, high-power, long-lived diode lasers have revolutionized the performance and operating cost associated with diode-pumped solid-state laser systems. In particular, diode pumping results in enhanced electrical-to-optical system efficiency since diode lasers emit optical energy over a narrow spectrum that closely matches solid-state absorption profiles. Additionally, reducing thermal gradients in the solid-state gain media improves beam quality and laser performance. The lifetime of high-power semiconductor laser devices, bars and arrays is several orders of magnitude larger than lamps, making diode pumping the ideal choice for present and future laser designs.
DPSS, ion and optically pumped semiconductor lasers enable front-end semiconductor manufacturing.
In front-end semiconductor manufacturing, lasers are mainly used in two applications: in lithography tools and in inspection. There are many different inspection steps in a modern semiconductor fab and Coherent lasers are used in most of them: mask inspection, bare and patterned wafer inspection. Coherent has many years of experience building lasers for these very demanding applications, which require ultra-high precision and no unscheduled down time.
Coherent lasers are used in a large number of advanced silicon wafer applications, both in high-volume production and in the development of tomorrow’s advanced chip architectures.
As silicon wafers get thinner and new material layers are added, lasers are playing a critical role in processing these wafers. As wafers get thinner, they become more difficult to process with traditional saws due to increased cracking and chipping. DPSS UV lasers like the AVIA can dice thin wafers with good throughput and edge quality. Similarly, the very brittle low-k materials that are so important in today’s advanced chips are best scribed by a DPSS UV laser. Lasers enable narrower street widths on the wafer further increasing overall yield.
Illuminating the semiconductor roadmap.
Laser technology’s role in semiconductor and microelectronics fabrication is growing exponentially as manufacturers seek to produce smaller, more powerful, reliable devices. More integrated components per area of silicon and reduced circuit geometries are the overriding benefits as lasers enable a complete range of semiconductor fabrication processes. As lasers trend towards shorter (UV) wavelengths, higher power and high reliability, they are expanding the bounds of semiconductor manufacturing.
Unparalleled Technology Depth
Coherent has the technology experience and diversity in all leading laser disciplines used in semiconductor and microelectronics manufacturing.
Like virtually every other branch of microelectronics, flex circuits are characterized by increasing miniaturization and the drive to decrease manufacturing costs. There is also increasing pressure to use greener fabrication methods. A new reel-to-reel process enabled by high power excimer lasers delivers tangible benefits in all three areas.
This direct patterning process takes advantage of the extremely high pulse energy of the LAMBDA SX laser. This is an industrial-grade excimer laser which can deliver 1050 mJ at 308 nm, at a repetition rate of 300 Hz. The high pulse energy is used to pattern circuits up to 400 mm2 in area with a single laser pulse. And at 300 pulses per second, this “single pulse” laser process can generate 18,000 circuits/minute.
The circuits are fabricated by vapor deposition of a uniform layer of metal (e.g., Au, Ag, Cu, Al) onto a flexible substrate such as PET, polyimide, PEN, or PMMA. The homogenized excimer beam is passed through a photomask, which is then re-imaged on this coated substrate. The high energy UV photons interact with the metal/substrate interface, directly removing the thin metal film in a pattern defined by the mask image. With a metal film thickness of 40 nanometers or less, a single laser pulse can perform a complete lift with clean edges and no breaks – even at linewidths of 10 microns or less.
The circuits can be fabricated using a reel-to-reel laser station with continuous motion of the web. The web motion appears “frozen” in the 30 nanosecond pulse duration. Or flying optics can be incorporated to enable roll-to-roll processing using stepped motion of the web. Some systems builders also incorporate a vacuum system which not only removes all the metal debris from the circuits, but also enables trapping and recycling of this valuable material.
This single-step dry process is now simplifying flex circuit fab and reducing overall fab costs by replacing traditional photochemical methods which involve seven (7) or eight (8) separate steps. Just as important, this laser-based method eliminates the need to use (and dispose of) wet chemicals. Furthermore, the various wet/dry cycles involved in traditional chemistry can cause shrinkage and deformation, limiting resolution and/or yields. This problem is no longer an issue with this new, single-step dry process.
Short and intense laser pulses provide unique benefits for many pulsed laser deposition applications.
Pulsed laser deposition (PLD) is a laser-based technique used to grow high quality thin films of complex materials on substrates like Silicon wafers. The material to be deposited (target) is vaporized by short and intense laser pulses and forms a plasma plume. Then, the vaporized target material from the plasma bombards the substrate and – under the right conditions – creates a thin homogenous layer on this substrate. For each laser shot, a layer of only a few nanometers of material is ablated to form the plasma plume in a process that typically last a few tens of picoseconds. To enable this process, nanosecond pulses with energies of tens or hundreds of millijoules are necessary and UV wavelengths are usually preferred. These requirements match well the performances of excimer lasers.
The first laser deposition experiments took place in the mid to late 1960s, but PLD gained tremendous interest after T. Venketesan in 1987 first applied this method to create high temperature superconductive (HTSC) films. Since then, many hundreds of lasers have been sold to drive research, process development and small-scale production of thin film devices, such as superconductive magnetic sensors (SQUIDs), thin film ferroelectrics and “high k” gate resistors, semiconductor alloys, carbon nano-tubes, and more.
Although visible or IR laser beams have been used for PLD applications, UV beams are now most commonly employed. Among UV pulsed lasers, excimer lasers provide a variety of short wavelengths combined with energy levels that fit perfectly most PLD applications. High laser pulse energy provides several benefits for pulsed laser deposition. First, it extends the range of possible target materials that can be used. Second, it enables a larger area on the target to be ablated with the desired fluence. In turn, this area enlargement increases the deposition rate and reduces the plume angle, resulting in higher deposition efficiency. Finally, higher pulse energy provides a larger process window, allowing a more consistent process.
Coherent’s COMPexPro and LPXpro laser series are designed for demanding high-pulse energy applications and are highly effective tools for pulsed laser deposition. They deliver the beam stability and energy stability performance required to achieve superior results in sophisticated thin film deposition experiments.
Since desktop inkjet printers are being produced with higher resolutions, there is a need for more and smaller holes in the nozzle array of the printing head.
The position of the holes, as well as the shape, must fulfill very tight tolerances (<1µm). While former products used electroforming for nozzle drilling, the excimer laser offers significantly better production yields and better control over the nozzle shape.
Coherent’s industrial excimer lasers are designed for high duty-cycle production with low maintenance downtime and low running-costs. State-of-the-art line beam optics are used for beam forming and homogenization. The results are up to 100 holes drilled simultaneously in patterns of up to 18 mm in length on the printer head that can be machined simultaneously with sub-micron accuracy.
The PCB industry is experiencing a tremendous increase in demand for multilayer boards (MLBs) and high-density interconnect structures (HDISs) driven by smart phones and tablets.
The extraordinary demand from smartphones and tablets, coupled with accelerating product cycles, has created a vigorous market for microvias and the equipment used to manufacture them in high volume.
There are four (4) microvia formation technologies: lasers, photovia, mechanical drilling, and plasma etching. Each technology has its inherent advantages and disadvantages.
The clear leader for blind microvias when considering cost per via, quality, size, and dynamic range and throughput is lasers. The following graph shows the dynamic range in hole sizes that the current laser technology offers
:As the leading supplier of lasers to the microvia industry, Coherent lasers are used to produce blind, buried or through microvias.
Coherent’s DIAMOND sealed CO2 lasers are used to drill >50 µm diameter vias in resin-coated copper (RCC), Fr4 and aramid-based dielectrics, as well as Cu-direct drilling processes.
The AVIA-series diode-pumped UV lasers are ideal for drilling <70 µm diameter vias in RCC and PTFE-based dielectrics and copper.
Excimer and fiber-based lasers enable industrial micromachining.
Ultraviolet (UV) laser light is an ideal tool for many micromachining applications. The short wavelength results in two major advantages: it allows the production of very small features and the effect on the surrounding material is minimal due to the non-thermal interaction.
There are two major technical breakthroughs that make UV lasers more and more useful in industrial applications. First is the dramatic maturation in excimer laser design. State-of-the-art excimer lasers using advanced technologies feature extended component lifetime, high reliability, low maintenance downtime and low running-costs. The second breakthrough is in the area of diode-pumped solid-state (DPSS) lasers. New generation lasers deliver high peak power, high repetition rates, and excellent beam quality (TEM00). They are also available with frequency conversion down to the fourth harmonic (266 nm).
Both advances make UV lasers more attractive to industrial users. As a result, they have been implemented in a wide range of micromachining applications. The following text outlines some important applications and specific laser requirements
.This photo shows excimer-micromachined script on a 120 micrometer diameter human hair. This is an example of high-resolution direct-ablation by mask imaging. This technique can produce resolved features down to a couple of microns.
Unique Application Examples for Excimer Laser Microstructuring
Images courtesy of Laser Laboratorium, Goettingen, Germany
MEMS combine mechanical and electrical functions on one chip, processed by traditional semiconductor techniques.
In the near future, gas sensors, chemical and biosensors, and actors like microvalves and microrelays will emerge. The field is now open for direct structuring of a wider range of materials and applications using UV lasers.
A very promising extension of 3D microstructuring has been explored by combining excimer laser ablation with the LIGA technique. Direct 3D microstructuring of the master by UV excimer light is much more flexible and economical than multi-step X-ray lithography.
DPSS and ion lasers enable laser lithography.
The Components of Lithography & Optics Testing
The rate of progress for optical lithography has been astounding. Twenty years ago, it was widely believed that optical technology for laser lithography would run out of steam at 0.75 mm. Progress in optical lens design, optical materials, optical manufacturing technology, and a steady reduction in the exposure wavelength, have resulted in the ability to print features of 0.18 mm in production today. Whenever the feature size is halved, the circuit density increases by four-fold. Smaller features, plus innovative circuit design and ever increasing chip sizes, has vastly increased the functionality per chip and has produced a bonanza of value and performance for the consumer. As long as the consumer has a sense of receiving more value for the computer dollar spent, consumers and corporations will continue to invest in upgrading their laser lithography systems.
Higher storage capacity of memory devices (DRAMs) and ever-faster clock speeds of microprocessors demand smaller circuit features, hence better resolution and smaller features in the lithography step. Larger optical field sizes are required for the more complex logic and storage devices and also provide higher throughput from the lithography equipment.
Laser Photolithography & Semiconductors
Laser photolithography requires UV both because it is easier to make UV sensitive resists and because deeper UV means better resolution.
There are two components to lithography:
Interferometric Optics Testing
Many applications use high-powered UV pulsed lasers for manufacturing operations. Some of these applications, such as semiconductor mask lithography, require extremely high pulse energies and demand UV optical components that are defect-free, low-absorption, and manufactured to within extremely tight tolerances.
Unfortunately, it is difficult to test these optical components with a pulsed laser system. The Innova 300 FreD provides a lower power CW UV source that can, without damaging the optical components, test these components before they are exposed to high power pulses. FreD’s 248 nm output line matches the wavelength of the KrF output of excimer lasers, and the 266 nm output from Azure matches that of the frequency-quadrupled output of a pulsed YAG laser.
The dramatic miniaturization of electrical and opto-electrical circuits and the growing need of high precision measurements of the shape of surfaces in industry are the driving force of the laser-based inspection market.
The laser is perfectly suited for high precision inspection, because of its high resolution and the various wavelengths available that can be selected according to the material under investigation.
What is Laser Inspection?
Laser inspection can be divided into two segments. One is the quality control of microscopically generated features and the determination of contamination in the semiconductor field. Microscopic laser inspection uses scattering, absorption and ultrasonic techniques to determine and locate a defect or a contamination of sizes in the range of the wavelength used. The Verdi series of CW solid-state lasers in the green and the Sapphire™ family in the blue cover scattering and absorption techniques, whereas the Vitesse family of femtosecond lasers serve ultrasonic applications.
Laser Inspection Equipment
The other segment in laser inspection is the determination of the quality of the macroscopic shape and its deviation to a reference. For this purpose, interferometry, shearography and holography using visible and deep UV wavelengths are widely used methods that achieve accuracy on the order of the wavelength employed. Coherent offers solutions to this ever-expanding marketplace with laser inspection equipment including the Verdi series (green - 532 nm), Sapphire (blue - 488 nm) and the Azure (deep UV - 266 nm). All of these lasers have the unique PermAlign™ technique for superior stability and lifetime. For the blue spectrum, Coherent offers the revolutionary Sapphire family at 460 and 488 nm.
Direct patterning of multiple layers plays a vital role in the Flat Panel Display (FPD) industry. The use of lasers helps meet the goal of lower manufacturing cost, high yields and environmentally friendly processing.
Direct laser patterning is achieved by various laser processes such as ablation, engraving, marking, or thermal treatment. Laser processing provides the advantage of being contact-free, flexible and highly reproducible. For most of these laser applications, the number of process steps is greatly reduced. Typical examples for laser direct patterning in the FPD industry include metal electrodes, contact holes, touch panel, and light guide plates.
To cover the large list of material mixes used in microelectronics and flat panel displays, Coherent offers a large product range of lasers. The range covers CO2 lasers for engraving, Direct Diode for thermal treatment, as well as DPSS and excimer lasers for ablation. Our lasers are perfectly matched to the direct patterning applications and provide the stability and robustness that is demanded by the industry. Global support and access to our fully equipped application centers are provided to ensure successful implementation.
Coherent lasers play a critical role in today’s advanced packaging and printed circuit board (PCB) applications, enabling smaller features, higher yield and higher throughput.
As feature sizes on PCBs continue to shrink, traditional printing methods are challenged to keep up with the precision requirements, particularly when it comes to multi-layer PCBs. Smaller features and more layers mean tighter and tighter tolerances on registration and control of the manufacturing process. Laser Direct Imaging (LDI), which uses a UV laser to directly write the desired pattern onto a photo-resist, solves or bypasses these problems and is becoming the manufacturing method of choice for the any layer boards now used in high-end smart phones. The Coherent Paladin family of lasers is the ideal source for LDI.
Laser crystallization drives faster, brighter displays with HD resolution. Excimer laser powers in excess of 1 kW and high precision UV optical systems are driving yield and productivity.
The trend towards mobile communications, smart phones, personal computing, and digital photo and video drives the market for advanced small and medium-sized displays with the highest resolution, high brightness and long battery life for a perfect user experience. For these displays, the LTPS (Low Temperature Poly Silicon) TFT backplane is inevitable to enable stable performance of AMLCD and AMOLED displays.
Coherent is the market leader for excimer lasers and UV optical systems that are the enabling components of the annealing system. Highest laser power of more than 1 kW and optimized line beams of up to 750 mm are used worldwide for the manufacturing of LTPS-based LCD and OLED displays.
Laser pulses can vary over a very wide range of duration (milliseconds to femtoseconds) and fluxes, and can be precisely controlled. This makes pulsed laser ablation very valuable for both research and industrial applications.
Laser Ablation is the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave (CW) laser if the laser intensity is high enough. The depth over which the laser energy is absorbed, and thus the amount of material removed by a single laser pulse, depends on the material’s optical properties and the laser wavelength.
Laser pulses can vary over a very wide range of duration (milliseconds to femtoseconds) and fluxes, and can be precisely controlled. This makes laser ablation very valuable for both research and industrial applications.
The 193 nm solid-sampling-system GeoLasPro is a self-contained laser ablation system for sample introduction in high-resolution LA-ICP MS (laser ablation inductively-coupled plasma mass spectrometry). GeoLasPro integrates the COMPexPro 193 nm ablation laser including beam homogenizing and shaping optics, a sample chamber, and unmatched microscopic sample observation capability. 193 nm sampling speed can be varied in a wide range from 1 Hz up to 100 Hz.
GeoLasPro includes several innovative features that enhance the performance of the overall LA-ICP-MS system. For example, the new sample observation microscope is made perfectly co-linear with the laser beam delivery optics through the use of an all-mirror microscope objective, which is free of chromatic aberration. This objective is also able to operate at higher laser power without the risk of coating damage that can occur when using lens-based objectives. These beam delivery optics can achieve a homogenized spot with a diameter as small as five (5) microns, which is ideal for sampling small fluid inclusions. The optics also include interchangeable circular and square beam shaping masks providing high sampling flexibility.
GeoLasPro is designed for geological and nuclear physics research and for quality control of materials and pharmaceutical samples. Examples include analysis of fluid inclusions in minerals, age determination of samples by isotope ratio analysis and analyzing high purity semiconductor materials
.Advantages of Laser Ablation
Solid-state lighting is a key element to achieve the global target for reduced energy consumption. Coherent lasers support this goal and drive new processes for advanced LED manufacturing.
The market for high-brightness light-emitting diodes (HB-LED) is poised for explosive growth over the next five years. Declining costs and improving performance have rendered HB-LEDs a viable competitor to conventional cold-cathode fluorescents (CCFLs) for backlighting flat screen televisions. Rapid adoption for LCD display backlighting is driving HB-LED market growth this time around.
The potential for HB-LEDs in general illumination such as retail display, outdoor, and residential lighting represents the largest overall market. Penetration into general lighting applications is expected to accelerate as manufacturing costs come down and device efficiency improves.
Novel laser-based manufacturing concepts such as laser-lift-off (LLO) processing with 193 nm and 248 nm excimer lasers enable vertical LED structures with increased light extraction efficiency.
Laser-based sapphire scribing, as well as wafer or substrate dicing with diode-pumped solid-state lasers at 266 nm and 355 nm or picosecond lasers, further reduce production costs and at the same time significantly enhance yield and efficiency of HB-LEDs.
The explosive growth within the electronics industry, driven primarily by telecommunications and portable devices, has resulted in an overwhelming demand for high-density flexible (HD flex) circuits.
Thanks to faster processing speeds, lower capital investment costs, higher quality processing, higher reliability, and the ability to process fine features, laser processing has proven to be an essential component for high-volume fabrication of HD flex. UV-DPSS and IR CO2 lasers offer the best overall solution to requirements set forth by flex manufacturers.
Laser technology can be used for a variety of applications within the HD flex industry: microvia drilling (blind and thru), excising, skiving, and coverlay processing. Coherent’s DIAMOND sealed CO2 lasers operating at 9.4 µm wavelength and AVIA-series diode-pumped UV lasers operating at 355 nm wavelength have become industry standards for laser flex processing.
Excimer lasers enable fiber bragg grating writing.
Photosensitivity is a non-linear optical phenomenon to describe a photorefractive effect in an optical fiber (i.e., a change in the value of the refractive index). A fiber irradiated by laser UV light will show a change in the transmission properties of the wave guides due to a permanent change of the refractive index.
Using an excimer UV laser to create an intense fringe pattern to irradiate the fiber, a permanent periodic modulation (spacing of the fringes) of the refractive index profile is photo induced giving rise to the periodic structure known as a Fiber Bragg Grating (FBG).
A Bragg Grating can produce a very precisely customised spectral profile allowing applications in filtering, wavelengths selections, Fabry-Perot etalon, and new types of sensors. The main use nowadays, however, is to allow a huge number of channels on fiber telecommunication and selecting the noise-free channels on wireless receivers of modern mobile phones.
Standard Optimization of the Excimer Laser aims for maximum Energy/Power, but is suboptimal with respect to Spatial Coherence
Optimization for spatial coherence achieves substantial improvements with little sacrifice in energy.
Sticking with a standard resonator design keeps alignment procedures easy for end users and is stable to temperature variation
Lasers are used to create periodic changes in the core refractive index of optical fiber.
UV lasers, including Coherent’s Innova Ion lasers, the LPXpro, COMPexPro and BraggStar series excimer lasers, are critical tools in the manufacture of high-performance fiber bragg gratings (FBG) for the Dense Wavelength Division Multiplexing (DWDM) marketplace. FBGs are used to perform a number of tasks in optical networks, including signal conditioning and routing. Ultraviolet (UV) lasers are used to imprint the gratings in the fiber.
The Innova Ion product line is a complete family of intracavity frequency-doubled argon lasers that produce high-power output in the deep-UV. The Innova Ion’s 244 nm wavelength is used to create periodic changes in the core refractive index of optical fiber. The resulting fiber gratings are used in DWDM technology, laser mirrors in fiber lasers, dispersion compensators, and gain-flattening amplifiers.
The Innova Ion lasers are used to produce a significant portion of high-performance FBGs.
The recent commercial boom in electronic devices and the trend toward miniaturization have caused ceramics fabricators to seek more efficient and precise manufacturing methods and tools.
Ceramic processing applications for lasers have increased since the development of several new industrial lasers. Lasers are now used to scribe, drill and profile, as well as for selective material removal and marking/serializing applications. They are also used to process fired substrates such as alumina (AL2O3 ), aluminum nitride (AIN) and beryllium oxide (BeO), and unfired (green) substrates.
Coherent’s DIAMOND sealed CO2 lasers, AVIA diode-pumped UV lasers and VECTOR diode-pumped solid-state lasers have become industry benchmarks for laser ceramics processing. These lasers are used for scribing, machining, marking and drilling of fired and unfired ceramic materials used as substrates in hybrid MCM and other microelectronics substrates.
Coherent supplies laser sources and tools for wire feed welding and brazing.
Coherent’s HighLight 4000L is a line source laser product, excellent for wire feed welding and brazing. The line spot of the 4000L makes feeding wire into the laser beam very easy. There is no need for expensive vision systems and precision alignment devices. The long beam which can only conduction mode weld “wets out” the weld. This produces excellent weld bead profiles.
Characteristics of conduction mode weld:
As with wire feed welding, the HighLight product line is an excellent heat source for Silicon Bronze brazing. For Body-n-White brazing, the HighLight 4000L is an excellent source for creating braze joints that do not need rework after brazing. The long beam wets out the weld.
Benefits of Laser Brazing
Direct from the computer to submicron dimensions using excimer lasers in the UV.
Excimer lasers can be used to shape a wide range of materials including polymers, metals, glass, ceramics and even diamonds. The direct-write approach using CAD/CAM software for laser machining in the dimensions of microns allows almost any shape to be generated on a surface.
The combination of compact excimer lasers and precision motion systems, video imaging and CAD/CAM software allows precision machining on scale-sizes in the 1 to 100 micron range.
Raster scanning on the work surface is one means of producing such three-dimensional structures. This technique forms the part by removing the material layer by layer.
Since the single-pulse ablation depth varies from a few nanometers to some tenths of a nanometer, it is possible to produce smooth, sloping surfaces with continuous height variation by excimer laser ablation.
Stereolithography, where 3D Models are created with an extremely high level of detail and a smooth surface finish, is an excellent choice where a close approximation to the finished product is desired.
Stereolithography (SLA) typically uses a low power UV laser to selectively harden a photosensitive epoxy polymer in a bath to form a part. Key benefits of SLA are high accuracy and smooth surface finish of parts. Extreme finish detail capability can be reached with a wide range of materials. SLA is used in various industries like Automotive, Aerospace, Consumer Products, Packaging, Electronics, Architecture, Medical and Government Research.
Coherent delivers unique UV laser technology by offering the Matrix UV DPSS laser. Customers count on Matrix due to its high reliability, excellent mode quality and pulse to pulse stability.
Coherent lasers enable the pattern tracing and hardening process that allows the 3D printer to transform a liquid curable photopolymer “resin” into a finished part.
The selective laser sintering process is ideal for parts that need to be durable, functional and withstand high heat and chemicals.
Selective Laser Sintering (SLM) builds up a part from polymer or metal powder by using a sealed off CO2 laser e.g. a DIAMOND C-Series laser or a 1 µm fiber laser. Key benefits of SLM are high accuracy and smooth surface finish of parts. Consistent part characteristics can be fabricated with a wide range of materials. SLM is used in various industries like Automotive Design, Aerospace, Defense, Heavy Equipment, Medical, Electronics, Consumer Products, White & Sporting Goods, Packaging, Home & Garden Equipment, Government Research.
Lasers are used to permanently mark an almost endless list of materials.
Laser marking can provide a permanent high-contrast mark on different types of plastics, allowing no direct contact with the plastic other than through the laser beam. A variety of results can be achieved when marking plastics.
Typically a CO2 laser with 10.6 µm is used for marking organic materials. The far infrared wavelength burns the surface of wood, paper, cork, leather and horn and typically creates a dark contrast. Organics and plastic materials can also be cut with lasers at high processing speeds with exceptional edge quality.
When marking metal surfaces, the high peak power of a 1 µm laser, such as a Matrix DPSS laser, engraves into the metal surface and creates a contrast. When using CW laser radiation, most steel, titanium and gold materials turn black creating an annealing contrast. If a green wavelength (532 nm) is used, most gold surfaces turn black and save precious material.
Cut organics and plastics including wood, acrylic and leather at high processing speeds.
|Organics and plastic materials can be cut with lasers at high processing speeds with exceptional edge quality. Non-metals such as plastics, fabrics, paper/cardboard, wood or leather are used in a wide range of industries including sign/advertising, fashion, automotive, furniture, and packaging. When cutting non-metals, the laser is used to evaporate or melt the material. Thicker material like acrylics for the sign industry or wood for die-board is typically cut with the use of a flying optic. A low pressure gas flow – typically compressed air - blows material out of the kerf and keeps the cut clean. The use of a galvanometric scanner is recommended when cutting acrylics or laser cutting wood when the material to be cut is very thin or very heat sensitive. The scanner moves the laser beam at very high speeds following the required cut contour inducing limited heat to the part. If the material cannot be cut in one pass, a multiple pass cutting process can be used. Scanner head assisted cutting is widely used in the electronics industry for de-paneling of PCB boards, or in laser-cut leather applications. The laser wavelength of 10.6 µm from a CO2 laser offers optimal absorption to cut non-metals. With the DIAMOND series, Coherent offers the broadest portfolio of sealed CO2 lasers ranging in power from 20W to 1 kW.|
Cost-effective, precision cutting of metals at varying thicknesses.
|There are two main cutting processes in metal cutting using laser technologies. These are fusion cutting and flame cutting. In fusion cutting, the laser beam melts the metal while a high pressure inert gas stream blows the molten material out of the kerf. Fusion cutting is used in the cutting of stainless steel and aluminum, leaving the user with a clean, shiny, dross free edge. Depending on the material thickness, up to a few kW of laser power maybe required. the cutting of mild (carbon) steel, flame cutting is used. The laser beam heats up the metal surface above a certain temperature such that a reactive assist gas, such as oxygen, causes an exothermic reaction and melts the metal. Flame cutting is faster than fusion cutting, but leaves an oxide coated edge. Flame cutting is faster than fusion cutting, but the edge quality of fusion cutting is better.|
|In Traditionally high power flowing gas or slab CO2 lasers have been used for both metal cutting processes. CO2 lasers offer better cut quality and can cut a wider range of materials. Coherent serves this market with DIAMOND CO2 lasers and has recently developed the HighLight FL-Series of fiber lasers to meet industry needs. The META 10C is Coherent’s laser cutting tool designed for the sheet metal industry.|
Joining composite materials requires different approaches than when joining metal materials. Laser welding can result in improved weld quality when the correct approach is utilized.
Welding carbon fiber composite materials requires different approaches than when joining metal materials due to its material properties. Bolting or riveting results in damaged and weakened material. Laser welding e.g. with our HighLight FAP system is possible if at least one of the welding partners has a thermoplastic resin and one partner is transmissive to laser radiation – cannot contain fiber. If both welding partners are thermoplastic, regular plastic welding applies (see page on plastics welding). If the CFRP partner is a thermoset, it requires pre-processing. The resin needs to be ablated by a laser so that the fiber structure becomes visible. In order to ablate effectively without impacting the fibers, a Q-Switched CO2 or UV laser e.g. AVIA applies. The open fiber structure enables higher shear strength after welding, as the molten thermoplast of the other welding partner flows around and in between the fibers. The open fiber structure of the CFRP causes swings in laser absorption during the welding process, leading to unreliable welds. A pyrometer controlled adjustment of laser power during the welding process improves weld quality by keeping the welding temperature constant.
By using a laser in the repair of large carbon fiber parts, precise repairs are conducted offering strength similar to that of a new part.
During the manufacturing process or during its final use of composites, damages may happen. While smaller objects might just be replaced and scrapped, larger parts need repair. Examples of these larger parts include an airplane fuselage damaged by a loading truck at an airport or bird damage of wind energy turbine blades. Traditionally, these carbon fiber repairs were done by either bolting a repair composite sheet on top of the damaged area or by manual grinding – scarfing the damaged area and refilling it with repair plys. The grinding process is preferred over the bolting process because it offers higher strength and reliability of the repair. Unfortunately the manual process involved in grinding is not repeatable and it requires high user skills. By using a frequency tripled DPSS laser emitting 355 nm like the AVIA, it is possible to precisely scarf the damaged area – allowing layers of composite to be ablated reliably and repeatedly. Laser repaired damages offer strength similar to that of a new part.
Diode lasers, with wavelengths in the range of 808 nm to 980 nm, are typically used to join various plastic material combinations in plastics welding applications.
Diode lasers are used to weld plastics, applicable for thermoplastic materials only. In one welding geometry example, the laser beam joins two materials by passing through the first transparent heating up the second absorptive joining partner. The latter one starts to heat up and melt. At the same time heat is transferred to the first partner and the two parts are joined. Laser welding of plastics becomes very attractive when particles caused by ultrasonic welding such as is found in the automotive or medical industry should be avoided. The high degree of automation and process control enables a high level of product quality.
Laser welding of plastics processes can be differentiated by contour, simultaneous, quasi-simultaneous and mask technology. By using the contour technology, a diode laser follows the contour in one pass. During simultaneous welding, the beam profile of the laser is shaped like the seam contour. During quasi simultaneous welding, a scanner head scans a higher power, high brightness diode laser beam at high speed along the contour and heats it up simultaneously. By using a mask, multiple small welds can be achieved by scanning a complete area. Coherent participates in the plastic welding segment by offering its HighLight FAP systems and OEM FAP systems.
Increase wear resistance and fatigue strength on the work piece surface.
Laser heat treatment increases wear resistance and increases the fatigue strength due to the compressive stresses induced on the work piece surface. In laser heat treating or case hardening, a spatially well-defined beam of intense laser light is used to illuminate a work piece. This light is readily absorbed near the surface and causes rapid heating that is highly localized to the illuminated area and which does not penetrate very deep into the bulk material. Depending upon the particulars of the part size, shape and material, the bulk heat capacity of the material typically acts as a heat sink for the extraction of heat from the surface therefore enabling self-quenching. The ability to precisely control the physical extent of the illuminated region, together with the short timescale of energy transfer into the material, gives rise to the main benefits of laser surface modification over other techniques. Several key benefits include rapid processing, precise localized control over case depth/hardness, minimal to no part distortion, superior wear and corrosion resistance and increased fatigue strength. Part geometry and carbon content (min. 0.3%) significantly influence the results that can be achieved with a laser heat treat process.
The wavelength of a High Power Direct Diode Laser (HPDDL), like the Coherent HighLight D-Series is very well absorbed by most metals in heat treating. This eliminates the need for surface preparation as well as the environmental compliance costs associated with emissions, clean up and disposal of the chemicals utilized in the painting process needed for other heat treating methods. The shape of the output beam from a HPDDL is also well matched to the needs of many heat treating tasks. Specifically, HPDDLs incorporate an optical design that integrates individual laser “beamlets” into a single beam with uniform power distribution; a typical nominal cross-section would be 3 mm x 24 mm. For the majority of laser hardening applications, the HPDDL output beam illuminates an area that is smaller than the total area to be processed so either the work piece or the beam (or both) need to be moved in order to achieve total coverage.
Laser cutting and scribing of display glass and functional foils are important processes for the Flat Panel Display industry. The contact-free laser processes enable the trend towards thinner glass and advanced material mixes.
Coherent lasers are the ideal source for microstructuring inside glass.
When marking and engraving glass, a high intensity laser irradiance enables a multi-photon process and non-linear absorption effects in transparent material such as flat panel display glass. The high peak power of the Matrix DPSS laser, easily engraves inside the glass.
Achieve optimal cutting speed and cut quality by using lasers to cut carbon or glass reinforced plastic.
Due to the fact that the melting point of fibers is much higher than the melting point of the resin, laser cutting of glass reinforced plastic and carbon fiber is challenging as the plastic tends to char and burn at the cutting edge. Best results have been shown by using lasers with very high peak power and short pulse length e.g. from a HyperRapid ps Laser. If operated at a high rep rate, good cutting quality can be achieved using a multiple pass cutting method. Optimal results were achieved also by using a UV laser wavelength e.g. from an AVIA laser. The downside of the multiple pass method is the low effective cutting speed and slow cycle time. Therefore, the multiple pass method is used mainly with thin materials. If some level of soot at the cutting edge is acceptable, high power fiber lasers like the HighLight 1000FL have shown the best compromise of cutting speed vs. cut quality.
Using lasers for cladding, you will achieve better surface uniformity than with traditional technologies.
|Coherent lasers offer superior overall clad quality, reduced heat input, minimal part distortion and better clad deposition control resulting in reduced dilution, lower porosity and better surface uniformity. Cladding is a well-established process used in a variety of industries for improving the surface and near surface properties of a part (e.g. wear, corrosion or heat resistance), or to re-surface a component that has become worn through use. Cladding typically involves the creation of a new surface layer having different composition than the base material by adding material to the surface. wavelength of a High Power Direct Diode Laser (HPDDL), like the Coherent HighLight D-Series, is very well absorbed by most metals. Its output is particularly well suited to the needs of laser cladding. Since the area illuminated by the laser beam on the work surface is typically smaller than the area to be clad, the beam is usually manipulated across the part. In the case of powder-based cladding with a free-space output system, the long axis of the line beam (up to 24 mm) is oriented perpendicular to the scan direction thereby enabling large areas to be processed rapidly. Alternately, in the case of wire feed cladding, it is usually advantageous to orient the beam such that the short axis is in the direction of travel.|
|The laser-based process offers superior overall clad quality, reduced heat input, minimal part distortion and better clad deposition control resulting in reduced dilution, lower porosity and better surface uniformity than traditional technology. The high quench rate of the diode laser produces a finer grain structure in the clad leading to better corrosion resistance. Finally, the line beam shape of the free-space laser can process large areas rapidly with a high degree of control over clad width and thickness, while also delivering lower operating cost and easier implementation than other methods.|
Cleaning the release agent off CFRP parts prior to painting or adhesively bonding is accomplished efficiently by using an Excimer laser.
Carbon composite parts are formed to their final shape in a mold. Release of the form is simplified by using a release agent, which is based on oil. Unfortunately, this release agent needs to be removed prior to painting or adhesively bonding parts. There are several suboptimal methods for removing the agent, such as manual grinding. Obviously this process is very time consuming and not repeatable. Through manual grinding, some fibers are damaged.
Lasers are able to remove the release agent, but the wavelength of the laser has to be chosen wisely. A 1 µm Nd:YAG laser transmits radiation through the resin and damages the fibers. CO2 laser wavelengths leave heat affected zones.
The most ideal wavelength for cleaning carbon fiber is UV radiation, as it selectively ablates the release agent and the resin surface, but not the carbon fibers. Excimer lasers at a wavelength of 308 nm are the ideal tool for fast and material-friendly cleaning and can achieve cleaning rates of up to 50m2/hour. Shear strength tests have proven that cleaning using an Excimer laser can be done repeatedly and efficiently with equal or better shear strength compared to traditional cleaning methods or longer wavelength lasers.
Laser welding operates economically in many different applications.
Laser welding operates efficiently and economically in many different applications, and can be used in place of many different standard processes.
|Laser keyhole welding is used when material needs to be joined with a higher thickness to width aspect ratio. High beam intensities heat the material upon evaporation temperature resulting in a deep capillary called a keyhole. Inert gas shields the process and protects it during the keyhole welding process from unwanted oxidization. By emitting single pulses with very high pulse intensity, spot welds can be achieved such as is used in the electronics industry. If seam welding is required, the focusing optic is moved after a keyhole is produced. The keyhole follows the weld seam resulting in a clean weld. In some applications such as in welding of car doors or seats in the automotive industry, a series of small welds on thinner material need to be produced within a certain area. In these instances, galvanometric scanner technology is used to steer the beam. The simplified motion of the scanning process combined with faster positioning and lower cost of ownership results in cycle time improvements. Traditionally high power welding applications are served by CO2 or Diode, Disk and Fiber lasers. Coherent serves this application with its HighLight FL series fiber lasers. Fine or spot welding is still served by lamp pumped solid-state lasers.|
|Heat conduction welding is applicable for sheet metal up to a material thickness of approximately 2 mm. A laser beam, focused on the seam, heats the material and that heat is quickly conducted through the sheets causing it to melt and join together. The focusing optic is moved along the seam while it focuses the laser beam to the sample, leaving a high quality weld. For Conduction welding, lasers with lower brightness, like direct diode lasers, can be used for this process e.g. the Coherent HighLight D-Series.|
Several high-throughput techniques rely on laser fluorescence.
DNA sequencing involves the use of automated and miniaturized biochemical techniques to determine the fundamental base sequence (ACGT) of strands of DNA, chromosomes and even the entire genome. DNA sequencing is characterized by its technological diversity, with several completely different high-throughput approaches, each promoted by their suppliers for their superiority in terms of accuracy (i.e., fewer read errors), maximum read length, and cost-effectiveness. These methods feature incredible parallelism that has enabled the cost of genome sequencing to fall by several orders of agnitude in less than 25 years. At present, the most popular of these techniques all rely on laser illumination of fluorescently tagged bases.
The diversity of methodology is reflected in the diversity of laser parameters needed for the different approaches. Some utilize tight focus and use just a few tens of milliwatts, whereas those that rely on wide-field excitation may use lasers at the 1 watt level and beyond. In order to track the four different bases, up to four different visible laser wavelengths are used depending on the fluorophore properties.
In terms of its usage and applications, DNA sequencing is widely used in research but is still in its infancy as a clinical tool. Oncology is a key application area with diagnosis, tumor gene profiling and customized therapies. Sequencing services are also offered as discretionary paid services to consumers fueling market growth. Ultimately, it is expected to play critical roles in the fast growing world of personalized medicine and emerging gene therapies.
High throughput methods key to modern drug discovery.
The use of arrays (well plates) revolutionized modern drug discovery and particularly screening, providing unique advantages including automation, miniaturization, and high speed. Array plates have gotten denser over the year and today can total as many as 1,536 separate wells, so imaging speed is of paramount importance in order to view all these wells at high resolution on a practical timescale. High performance array readers are used to image these arrays that are also used in academic research. The combination of laser-based confocal imaging and fluorescent markers in these readers now enables individual cells and even sub-cellular components to be mapped with three dimensional (depth) resolution.
Compact and cost-effective visible lasers with plug-and-play functionality have enabled the development of these next generation array readers, where up to five different excitation wavelengths are used of multi-parameter screening. These wavelengths range from violet/UV 405 nm to red (630 nm). In this way, the same reader might automatically map a genetically expressed fluorescent protein, a nuclear label like DAPI, a membrane stain, and a mitochondrial marker, all in the same fast measurement cycle.
Raman scattering is a valuable spectroscopic technique that can be applied to solid, liquid or gas samples.
The Raman effect occurs when a sample is irradiated with UV, visible or IR light and a small fraction of the incident radiation is scattered and shifted at frequencies that correspond to vibrational transitions specific of the sample.
The Raman signal is much weaker than the incident and scattered light, so it may be difficult to detect it, unless appropriate measures to enhance the signal/background noise ratio are taken. For example, when a laser source is tuned to match an electronic transition of the sample, the resonant effect increases the Raman scattering by several orders of magnitude. This so-called resonance Raman spectroscopy is often used for applications such as qualitative analysis and molecular structure determination of samples which exhibit electronic transitions in the visible region of the spectrum. For non-resonant Raman spectroscopy, the most commonly used sources are visible or IR laser sources in the range 500 nm to 1,000 nm; shorter wavelength are more likely to excite fluorescence that can easily hide the Raman scattered light, unless the fluorescence is carefully filtered out. For this reason, near-IR light is often used.
Laser sources for continuous wave (CW) Raman spectroscopy include laser diodes, diode-pumped lasers, optically pumped semiconductor lasers (OPSL), and ion lasers. For excitation at fixed wavelengths with CW solid-state lasers, Coherent offers the Sapphire SF single-frequency OPSL series with wavelengths at 488 nm and 532 nm. The Innova 300C and 70C series of small-frame argon or krypton ion lasers are also well suited for Raman experiments in the visible region of the spectrum. Innova 70C Spectrum is a mixed gas lasers that can generate a number of laser lines from the UV to the near IR.
Ultraviolet (UV) resonance Raman spectroscopy is a useful tool for the investigation of molecular structure, kinetics, and excited-state surfaces and dynamics. In particular, it finds numerous applications in systems of biological interest. The Innova series of frequency-doubled argon ion lasers - Innova FRED - is perfect match for resonance Raman spectroscopy because it produces several wavelengths in the range 229 nm to 257 nm. The very short wavelengths of these CW lasers minimize sample damage, compared with nanosecond pulses lasers, and minimize excitation of competing fluorescent signal.
A dynamic field of Raman studies is coherent anti-Stokes Raman scattering, or CARS. This technique uses two synchronized picosecond or femtosecond sources to stimulate a strong signal response at the so-called Anti-Stokes frequency. This happens only when the wavelengths of the two lasers are separated by a wavenumber matching the Raman transition of the sample. This technique is particularly suitable to detect lipids (fats) in microscopic cellular specimens. Ti:Sapphire (Ti:S) lasers and OPOs are well suited for CARS experiments: broad tunability and flexible pulse duration match the application requirements perfectly. Mira-900, Chameleon and Mira-OPO are ideal laser sources for CARS.
Delivering superior results with reduced patient discomfort.
Photocoagulation is the prescribed first-choice intervention method for wet-form macular degeneration and diabetic retinopathy, conditions which are estimated to affect up to 250,000 people annually in the U.S. alone. Moreover, this age correlated condition will become even more prevalent with the aging of the baby boom generation.
The Genesis 532 M and 577 M laser family is perfectly suited for photocoagulation treatment of wet-form macular degeneration and diabetic retinopathy. It provides up to 8000 mW at 532 nm and for the unique yellow wavelength of 577 nm up to 5W. This new yellow wavelength is exclusively available from our proprietary OPSL technology and exactly matched to the main absorption peak of oxygenated hemoglobin. It provides a higher degree of tissue selectivity than any previous laser wavelength. This delivers superior results with reduced patient discomfort.
A rapidly growing field combining molecular biology with optical stimulation of light-sensitive proteins to target specific regions of a single cell or a group of cells within the brain.
Optogenetics is about turning on and switching off neurons by optical stimulation using light sensitive proteins. The first light-activated proteins isolated from a species of green algae in 2002 were Channelrodopsin-1 and -2. When activated with appropriate light, these proteins open the channel for a flux of positive ions into the cell to activate neurons and to trigger voltage signal propagation (the so-called action potential). Halorodopsin does the inverse (with negative ions) to deactivate neurons.
Multiphoton Excitation (MPE) microscopy was first reported in 1990 (Denk, Strickler and Webb). Since then, it has grown to become an ubiquitous imaging technique when in-vivo, optical sectioning is key. In multiphoton microscopy, a fluorescent molecule – attached to the specimen or naturally present – is excited by two or three photon of infrared light. This is in contrast with confocal microscopy where the same type of molecules are excited by a single photon of blue-green or UV light. Multiphoton excitation offers several fundamental advantages over confocal microscopy: the IR light penetrates more deeply in the tissue because of lower absorption and scattering; the longer wavelength is less damaging and allows in vivo imaging also in human subjects; finally, the non-linear process excite fluorescence only on the focal plane and a the confocal aperture required with single-photon excitation is no more necessary. The sectional image of a living mouse brain, imaged to a depth of 800 micron with Coherent Chameleon Ultra II laser is an impressive paradigm of the capability MPE.
In parallel to MPE, several other non-linear techniques have become increasingly popular. These include Second Harmonic Generation (SHG) microscopy and Coherent Anti-Stokes Raman Spectroscopic (CARS) microscopy. This suite of non-linear techniques require the use of Ultrafast lasers, generating pulses of 100-200 fs and tunable over the near IR region of the spectrum. These lasers are inherently more complex than the blue-green lasers used for confocal microscopy and other bioinstrumentation applications.
Coherent recognizes that microscopists, neurologists and biologists should not have to become laser experts to do their work. For this reason we designed and manufacture and expansive line of lasers designed specifically for non-linear imaging. This way, MPE users can focus on their sample, not on the laser equipment.
Learn more about Multiphoton Excitation Microscopy by visiting our OASIS™ page.
Coherent partners with medical system builders across the globe to provide the laser technology necessary for them to manufacture a variety of medical components.
Medical devices encompass a broad range of solutions that can host a variety of different laser technologies from the UV to the mid-IR range. Using the right wavelength for a specific material provides efficient machining and throughput. Defined by the level of precision needed, laser solutions range from short pulse (nanoseconds) to ultrashort pulses (picoseconds). Ultrashort pulses minimize heat affected zones and, combined with “cold machining” processes, offer the highest level of precision beneficial for the most demanding applications such as stent manufacturing.
Myopia, astigmatism, and hyperopia can all be treated effectively with non-thermally damaging and precisely controlled lasers.
Laser vision correction has revolutionized eye surgery. Myopia, astigmatism, and hyperopia can all be treated effectively with the non-thermally damaging and precisely controllable ArF excimer laser beam. This technique has already helped millions of people since the early 1990s to enjoy life without glasses or contact lenses. Coherent is the leading supplier of light sources for this rapidly-expanding industry.
By being the first to engineer extremely reliable, high-repetition-rate excimer lasers specifically for this application, we have become the supplier of choice for many industry leaders in vision correction. Being successful in this industry depends not only on laser performance, but also on the quality of the system. Because laser vision correction is not a medical necessity, it is considered cosmetic surgery and as such it is closely supervised by the FDA and other regulatory agencies around the world. These regulatory bodies require the highest standards in product quality and safety.
All Coherent systems meet or exceed these standards and we continue to maintain and improve our comprehensive ISO 9001:2000 quality-management system.
Today, Coherent is the leading supplier of excimer lasers for refractive error correction systems. At least 35% of all refractive surgeries (more than 1 million procedures annually) are performed with our lasers. We continue to be the industry leader as we supply the next step in refractive surgery technology: customized vision correction.
The diagrams show the principle of cornea reshaping for myopic and hyperopic vision correction and laser application. The accuracy of the ArF excimer laser ablation is essential for the predictability and safety of laser vision correction. Only this laser source enables the precise reshaping in the necessary sub µm range.
Images courtesy of VSDAR, Munich
Correction of refractive errors (shortsightedness and farsightedness as well as astigmatism) with an excimer laser is a safe and effective procedure which can restore the natural vision of the patients.
Providing a minimally invasive solution to filtering microsurgery.
Glaucoma is a group of eye diseases that gradually steals sight without warning and often without symptoms. Vision loss is caused by damage to the optic nerve. This nerve acts like an electric cable with over a million wires and is responsible for carrying the images we see to the brain. 1-2 % of the population suffer from the most common form: primary open angle glaucoma, making it the most frequent cause of blindness in industrialized countries.
Excimer Laser Trabeculotomy ELT can help patients with primary open angle glaucoma. The laser beam opens the fluid channels of the eye, helping the drainage system to work better. A tiny needle transmits the laser light directly to the trabecular meshwork. The procedure can be conducted in a matter of minutes by ophthalmic surgeons in an outpatient clinic.
Excimer Laser Trabeculotomy ELT enables to effectively treat primary open angle glaucoma in an outpatient clinic in a matter of minutes. It has shown to be an effective method to reduce the intraocular pressure significantly, making it the the minimally invasive alternative to filtering microsurgery (trabeculectomy).
Flow Cytometry is a diagnostic tool most commonly used to analyze the immune or genetic characteristics of cells.
Cells from a sample are mixed with a dye which preferentially binds (called tagging) to a cellular component. The sample is then illuminated with laser light, causing the dyes to fluoresce. The fluorescence emission is spectrally filtered to separate the signals. Quantitative analysis of the respective signal strengths yields a distribution of the blood components within the sample. The current generation of dyes is excited by 488 nm laser light.However, recent work suggests that a new generation of dyes which fluoresce when pumped by 532 nm light can provide even more information.
Our Sapphire laser portfolio began with the offering of the world´s first solid-state 488 nm laser. This diode-pumped laser family offers significant performance, size and efficiency advantage over traditional air-cooled gas lasers. For recent progress with 532 nm excitation, we offer the Compass family of DPSS lasers. Our CUBE and Genesis lasers also offer products with wavelength ranges ideal for fluorescence emission.
Coherent laser bars and systems, with increasingly higher power-spectral density, enables exciting new possibilities.
Unlike the mature technology of conventional MRI, enhanced MRI technology and applications are still evolving and therefore require a flexible and well designed laser to meet the demanding needs of both OEM customers and research laboratories. The latest generation of Coherent semiconductor laser bars and systems, with increasingly higher power-spectral density, enables exciting new possibilities and emerging novel applications for laser induced hyperpolarized noble gas imaging.
By offering the widest variety of wavelength options and allowing the end user to easily exchange different wavelengths in a few minutes, Coherent diode lasers offer the flexibility to pump rubidium, potassium, and other atomic vapors used in the spin exchange process.
Coherent provides a broad range of CO2, Excimer and OPSL laser solutions to enable effective dermatological procedures.
In the field of dermatology we serve a number of applications. Our CO2 lasers and semiconductor diode lasers are widely adopted in the areas of tattoo removal and hair removal, and our waveguide technology with CO2 lasers is the leading technology in the rapidly growing fractional skin resurfacing application. More recently, system builders have begun to use our visible Optically Pumped Semiconductor Lasers (OPSLs) in the treatment of pigmentation, blood vessels or wrinkles because of its better absorption of yellow wavelengths in melanin compared to legacy green laser solutions.
Breakthrough treatments for psoriasis and vitiligoPsoriasis are being discovered. These are chronic, recurring skin conditions with no known cure. It produces red, scaly skin plaques that causes discomfort and disfigurement. It is the second most common skin disorder in the United States, Europe and Countries with little sun exposure. The cost for conventional treatment approaches such as phototherapy (broadband UVB, PUVA), topical and systemic medication sum up to high expenses and promise only temporary relief.
Several large multicenter clinical trials have demonstrated the success of a new 308 nm laser therapy to treat the symptoms of Psoriasis. A beam generated by an excimer laser is aimed precisely at the involved skin without exposing normal skin, reducing the risks of conventional phototherapy such as photoaging.
In contrast to traditional treatments first results are visible after only a few treatments and they promise to be long-lasting, symptoms disappearing for 6 or even more than 12 months. Most patients heal in between 6 and 12 sessions, vastly reducing the number of required treatments and increasing compliance.
Recently introduced the new laser treatment is now revolutionizing the psoriasis therapy. Patients with small plaques (up to 35cm²) can be treated within one minute, for patients with larger lesions and dark skin types the treatment may take 5 to 15 minutes.
For the first time a quick and effective treatment for psoriasis can be offered, ending patient and doctor frustration. The intense, narrow band 308 nm radiation of the XeCl excimer laser has shown to be very beneficial for the treatment of vitiligo and leukoderma as well.
(Photos courtesy of Dr. H.M. Ockenfels, Hanau, http://www.laserzentrum-rhein-main.de)
Yields a series of high-resolution, high-contrast images that can be reassembled into a three-dimensional picture.
The microscope is confocal because the objective lens is used both to illuminate the sample and to image it. It is a scanning optical microscope because only one point of the sample is illuminated at a time. As the sample is scanned, the image is built up pixel by pixel. True optical sections of a sample are taken because of the short focal plane of the objective lens (as small as .5 microns). Any image data above or below the focal plane is prevented from reaching the detector. Levels of the sample are collected as the focal plane (Z axis) is raised or lowered. These levels are then computer-assembled into a three dimensional structure. Features of a confocal microscope include high-resolution, submicron microscopy, without the expense of an electron microscope, magnification ranging from 100x to 10,000x, and non-destructive examinations of living samples. Confocal Microscopes are used in the following applications:
Confocal Microscopes are used in the following applications:
Coherent lasers are used in a wide variety of biomedical applications from flow cytometry to DNA sequencing.
Bioinstrumentation applications, ranging from flow cytometry and cell sorting to microscopy, DNA sequencing and retinal scanning, use lasers to excite fluorescence from a variety of probe molecules. These fluorescent probes help researchers and clinicians perform a variety of important tests at both the cellular and molecular levels.
Efficient and reliable illumination sources for bio-detection and biomedical applications.
Coherent’s structured light lasers, when used in conjunction with our Flat Top Projector refractive beam shaper, can illuminate an area with uniform intensity for use in applications where scanning or inspection of biological molecules over a given area is necessary. New developments in the photonics field and the increase in demand for biological agent identification systems have created a new need for efficient and reliable illumination sources for such applications.
Laser process tools enable ultra-narrow c-Si solar cell line scribing
for edge isolation while minimizing sub-surface damages such as
Laser process tools for solar cell Edge Isolation all feature AVIA lasers; currently the dominant laser source for c-Si UV-laser Edge Isolation, with over 90% market share. Within laser Edge Isolation, a high-speed scanner directs UV or green nanosecond laser pulses around the perimeter of cells, scribing narrow grooves between the finger grid and the cell edges. The use of short-wavelength laser output enables ultra-narrow scribe lines (<30 μm), reduced ‘dead’ area around the trenches, and minimized sub-surface laser damage. Sub-surface damage – a negative outcome of using long wavelength IR lasers – can include changes to minority carrier lifetimes and bulk microcracking.
Coherent lasers enable highly precise scribing and doping processes for c-Si selective emitter formation.
Selective Emitters hold perhaps the greatest promise for efficiency enhancement within c-Si solar cell production. Laser-based tools have various roles within the different schemes already implemented or which form the basis of tomorrow’s high-volume production lines. Laser scribing (with short-wavelength nanosecond AVIA lasers) is performed at the front-end of Laser Grooved Buried Contact (LGBC) cells. Laser-assisted Dopant-Diffusion (either using the residual PSG layer or pre-deposited impurities) enables direct formation of strongly phosphorous doped regions. Here the short pulsewidths and fast (quasi-CW) pulsing from Paladin laser-based tools are ideal for production environments. Laser ‘doping’ can also be performed simultaneously with groove scribing or Dielectric Ablation.
Lasers and laser process tools enable highest precision c-Si ablation with minimized sub-surface bulk damage.
IOS tools for Edge Isolation all feature AVIA lasers; currently the dominant laser source for c-Si UV-laser Edge Isolation, with over 90% market share.Within laser Edge Isolation, a high-speed scanner directs UV or green nanosecond laser pulses around the perimeter of cells, scribing narrow grooves between the finger grid and the cell edges. The use of short-wavelength laser output enables ultra-narrow scribe lines (<30 μm), reduced ‘dead’ area around the trenches, and minimized sub-surface laser damage. Sub-surface damage – a negative outcome of using long wavelength IR lasers – can include changes to minority carrier lifetimes and bulk mAlso known as Selective Removal, Dielectric Ablation involves ablating thin layers of SiNx or SiO2 included on the cell surfaces to increase surface passivation while further assisting light transmission (front) or reflection (rear). Laser-based tools can ablate fine lines or holes with micron precision, while reducing sub-surface bulk damage to levels not affected by subsequent downstream process steps. Dielectric Ablation is a prerequisite for diffusion or plating mask formation/openings – both strong candidates for next-generation highefficiency cells. Key laser specifications include both short-wavelengths and short pulsewidths; factors which promote the AVIA, Talisker, and Paladin lasers.crocracking.
Coherent lasers are ideal for thin-film panel production due to their excellent pulse-to-pulse stability, accurate beam positioning on the panels, and a combination of short pulsewidth and high repetition rates greater than 100 kHz.
Thin-Film panels are actually comprised of a large number of thin ‘cells’ - or strips - that are interconnected to allow low-voltages to be added up in series across the panel, while keeping the current generated from the panel at a low level of a few amps. Dividing up these panels into cells involves the use of lasers to ‘pattern’ the layers during the Thin-Film deposition stages. Lasers have been the preferred technology for Thin-Film Patterning from the inception of Thin-Film production over ten years ago. As a result, this application for lasers within the Solar industry represents the area where lasers are most commonly used and have the highest visibility levels.
Each of the common Thin-Film absorber-types (a:Si, CIGS, Cd:Te) requires three Patterning stages (termed P1, P2, and P3). While a range of different materials is found across Thin-Film manufacturing, the Patterning steps are most typically performed with relatively low-power (up to 20W) short-ns-pulsewidth diode-pumped solid-state lasers, either at 1064, 532, or 355 nm. The choice of wavelength is typically due to the absorption properties of the materials used. Decreasing the pulsewidths can provide cleaner selective material removal: increasing the repetition rates can increase the process time on larger panel sizes.
AVIA based process tools enable highly reliable and precise c-Si wrap through processes.
Laser based tools can also be configured for ‘Wrap-Through’. This includes both Emitter and Metal Wrap-Through schemes. Here conductive pathways (via’s) are drilled through c-Si cells to allow contacts to be located at the rear of the cells; busbars for MWT and both fingers/busbars for EWT. With a ten-year heritage in drilling Through Silicon Via’s (TSV’s) within the semiconductor industry, the AVIA laser-based laser process tools provide ideal platforms here. Finally, various short-wavelength lasers provide the basis of front surface mask hole openings for etch-barriers, used in new concepts to texture the surfaces of multi-crystalline cells.
With a wavelength range from 460 nm to 639 nm, our high power Taipan
lasers come in a variety that fully satisfies all entertainment laser
Coherent Taipan lasers offer the practical advantages of small size, low power consumption, high reliability and the ability to be directly modulated, while also providing a broader palette of colors to the show designer than ever available before. In addition, Coherent continues to offer diode-pumped solid-state green lasers for the entertainment and display industry.
Lasers are a vital tool in the expansion of memory capacity of data storage.
Various groups throughout the world are developing new materials to be used as optical data storage material, while many computer companies are investigating methods of expanding the memory capacity of their current systems. Many optical disk systems are equipped with 780 nm laser diodes. These diodes are compact, reliable and inexpensive. However, they impose a limit on memory density due to the achievable spot size (numerous other factors also influence memory capacity).
Changing to visible light sources would overcome the limitation, since they would yield smaller spot sizes for the same M2 value. Visible DPSS lasers obviously provide a high-quality mode, but their current size and cost is not consistent with the needs of the desktop computer market. However, the laser diode can be easily replaced by a DPSS laser.
With a wavelength range from 460 nm to 639 nm, our high power Taipan lasers come in a variety that fully satisfies all entertainment laser applications.
Based on Coherent’s unique optically pumped semiconductor laser (OPSL) technology, these all solid state lasers deliver both the requisite collimation and beam pointing for this very demanding application. Moreover, the wavelength scalability of this technology supports balanced color, (i.e., true color/white images) by use of wavelength-optimized red, green and blue Taipan laser modules. And just as important, Taipan lasers provide high reliability ensuring the show goes off flawlessly with not a single laser having any problem. Plus, the combination of reliability and remote hands-free operation meant that your entire laser show could be controlled from one console by a single individual.
Coherent lasers deliver sufficient power with long coherence lengths for many holographic applications. They are frequency stable and exhibit exceptional power and pointing stability.
Holography is the process by which three-dimensional visual information is recorded on a high contrast, very fine grain film. A hologram refers to the flat “picture” that displays a multi-dimensional image under proper illumination. Unlike a photograph, a holographic image has “parallax” (the ability to see a scene from many angles) and depth to give the image a real life quality. And, unlike a regular photograph, a hologram records the image’s diffraction pattern, not the actual image. This is achieved by creating an interference pattern between two wavelengths of light that are in phase. The object that is being recorded must by illuminated by a coherent light source such as a laser.
The quality of a hologram is dependent upon numerous factors including exposure time, laser linewidth, frequency stability, power stability and pointing stability. Minimizing the exposure time is generally desirable since this reduces the effects of the environment
(e.g., vibration). Ample illumination power is a good solution. Narrow laser linewidths/long coherence lengths are essential when there are large pathlength differences. Variation in the laser frequency during holographic recording shifts the interference pattern and smears the hologram. The need for power and pointing stability is obvious.
Holography is also used as a tool in the medical, semiconductor and photonics industries.
The use of laser pulses to find range or other information of a distant target.
ght etection nd anging uses the same principle as RADAR. The LIDAR instrument transmits light out to a target. The transmitted light interacts with and is changed by the target. Some of this light is reflected or scattered back to the instrument where it is analyzed. The change in the properties of the light enables some property of the target to be determined. The time for the light to travel out to the target and back to the LIDAR is used to determine the range to the target.
There are three basic generic types of lidar:
Range finder LIDAR is used to measure the distance from the LIDAR instrument to a solid or hard target.
fferential bsorption LIDAR (DIAL) is used to measure chemical concentrations (such as ozone, water vapor, pollutants) in the atmosphere. A DIAL LIDAR uses two different laser wavelengths which are selected so that one of the wavelengths is absorbed by the molecule of interest whilst the other wavelength is not. The difference in intensity of the two return signals can be used to deduce the concentration of the molecule being investigated.
Doppler LIDAR is used to measure the velocity of a target. When the light transmitted from the LIDAR hits a target moving towards or away from the LIDAR, the wavelength of the light reflected/scattered off the target will be changed slightly. This is known as a Doppler shift - hence Doppler LIDAR. If the target is moving away from the LIDAR, the return light will have a longer wavelength (sometimes referred to as a red shift), if moving towards the LIDAR the return light will be at a shorter wavelength (blue shifted). The target can be either a hard target or an atmospheric target - the atmosphere contains many microscopic dust and aerosol particles that are carried by the wind. These are the targets of interest to us as they are small and light enough to move at the true wind velocity and thus enable a remote measurement of the wind velocity to be made.
For more information on defense technologies, visit:
Coherent lasers enable an environment-friendly process that saves production time.
The printing industry has traditionally depended upon silver-halide films and chemicals to engrave printing plates. This toxic chemical engraving process is accomplished in several time-consuming steps.
Working with professionals in the printing industry, Coherent’s research and development group designed ultra-compact solid state laser systems to simplify the engraving process. These systems play a role in creating the market for computer-to-plate printing—an environment-friendly process that saves production time by using diode-pumped lasers to write directly to plates.
Coherent has locations across the globe that are available to provide support for any product, service or inquiry.
5100 Patrick Henry Drive
Santa Clara, CA 95054 USA
Coherent has locations across the globe that are available to provide support for any product, service or inquiry.
Cohérent possède des sites à travers le monde qui sont disponibles pour fournir un support pour tout produit, service ou demande.
14-16 Allée du Cantal
Coherent has locations across the globe that are available to provide support for any product, service or inquiry.
Room 1006 – 1009, Raycom Info Park Tower B, No. 2, Kexueyuan South Road Haidian District
Direct connection to sales team : 02-3419-8039 Direct connection to Service team : 02-460-7999
서울특별시 성동구 광나루로6길 20 (성수동2가) 이글 타운 1층, 5층, 6층
5100 Patrick Henry Drive
Santa Clara, CA 95054 USA
Toyo MK Building 7-2-14 Toyo, Koto-ku
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