Wavelength beam combining of laser sources has been demonstrated for diode laser arrays 9,10 and ber lasers. In contrast, coherent beam combining cbc consists of the superposition of individual laser beams by constructive interference into one highpower laser beam. Pdf challenges in coherent beam combining of high power. This could be satisfied by developing a parallel but generic technology of laser beam combiner. Passive and active fiber laser array beam combining by weizung chang a dissertation submitted in partial fulfillment of the requirements for the degree of doctor of philosophy electrical engineering in the university of michigan 2012 doctoral committee. Laser liftoff separation is the enabling technology in manufacturing flexible displays. A brief summary of the major beam combining approaches is in table 1. Coherent combining and phase locking of fiber lasers. Spatial combining of laserdiode beams for pumping an npro. The effect of polarization in passive coherent beam. The goal is to combine several highpower laser beams so as to obtain a single beam not only with correspondingly higher power but also with more or less preserved beam. Prospects for single coherently combinable high power fiber amplifier, beam tilling and targetintheloop control for propagation in real atmosphere are presented. Wavelength beam combining for power and brightness scaling of.
Coherent beam combining with multilevel optical phase. Beam combining of laser arrays with high efficiency and good beam quality for power and radiance brightness scaling is a longstanding problem in laser technology. Leger, university of minnesota, minneapolis, usaabstractlaser beam combining is currently seen as the primary route to high optical radiance in many laser systems. First, a mathematical formalism is developed to study cavity dependent properties, in particular, the modal response of complex laser systems. Even with correct optics for beam combining, if the frequency of each beam added isnt phased properly, its beam becomes a subtractive element, not an addition. Incoherent beam combining of fiber lasers by an allfiber 7. Professor almantas galvanauskas, chair professor karl m. Fast adaptive laser shaping based on multiple laser. One step further, coherent beam combining cbc also helps to maintain the very unique properties of the laser emission with respect.
A homemade dammann grating is employed as a passive beam combining optical element. Wav elength beam combining of quantum cascade laser arr. It allows a to increase the output power and brightness of singletransversal mode laser. The emission wavelengths of the lasers are selected by the individual dfbs on each laser ridge in the array.
We present numerical and experimental results of 3 applications of this shaper. Organized fiber beam combining coherent laser beam. Coherent and wavelength beam combining have multiplied their output power in the past few. Thermallensfree cooling of solid state lasers for coherent beam combining kenichi ueda1,2,3,4 1 inst. Coherent beam combining of high power fiber lasers. Basically, the new technique involves shooting several laser beams at a very pure diamond, which due to its lattice properties combines the incoming beams into one outgoing beam, and at the same time changing its frequency.
As the ability of pumping andor cooling of a single laser is saturated, several similar lasers can be. A modal approach is used to explain complex resonator behavior. Laser beam combining techniques allow increasing the power of lasers far beyond what it is possible to obtain from a single conventional laser. Coherent beam combining cbc technology holds the promise of enabling laser systems with very high power and nearideal beam quality. Learn more about optoelectronics research centre research. Coherent addition or coherent combining of lasers is one of methods of the power scaling. Active phase control on the passive phased pulsed laser array using stochastic parallel gradient descent algorithm. Cbc opa laser systems enable the digitalization of materials processing. The book is intended to be an overview of this much researched area and it does a very good job of introducing the reader to the various methods and techniques constructed and tested with laser diodes, fiber lasers and even co2 lasers. Uvblade excimer laser line lengths and energy density systems for laser liftoff applications uvblade gently detaches delicate polymerbased displays of all types from their rigid glass carriers. Collapses and nonlinear laser beam combining department of mathematics and statistics, university of new mexico, usa pavel lushnikov support. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the united states government.
Modelocked pulses in passive coherent beam combining fiber laser arrays by chao zhang a dissertation submitted in partial ful. A wide variety of approaches have been developed since the early designs of the 1980s, resulting in a wealth of optical techniques and. Fan surveys current methods under study for beam combining. It allows a to increase the output power and brightness of singletransversal mode laser usually, the term coherent addition applies to fiber lasers.
Understand different laser beam profiling technologies. Chapter 4 application of oplls in coherent beam combining 4. We propose and demonstrate a novel servo system composed of multilevel optical phase lock loops. B 1 spectral beam combining b sc n x b 1 superposition of. However, no matter how accurately and diligently a profile is measured, this information does not predict the intensity distribution elsewhere along the beam path. Laser beam combination is the process of combining multiple laser beams into a single output beam, to increase the output power and beam brightness, ideally far beyond what it is possible to.
Wavelength beam combining the general principle of wavelength beam combining is to take spatially separated beams with distinct optical spectra, and combine them using a wavelengthsensitive beam combiner 8. Laser beam combining methods, motes, andrew, ebook. Incoherent combining of fiber lasers developed for directed. Allfiber 7x1 signal combiner for incoherent laser beam. Incoherent combining of highpower fiber lasers can result in highly efficient, compact, robust, low maintenance, and longlifetime highenergy laser systems for directed energy applications. It is shown that the coherent beam combining in these common cavities is extremely sensitive to random pathlength variations of the individual gain elements. Beam combining is accomplished by a suitably placed grating and transform lens that overlap the beams from. The chapter analyzes the properties of passively cophased fiber lasers in terms of spectral behavior, stability, and dynamics. Jun 11, 20 incoherent combining of highpower fiber lasers can result in highly efficient, compact, robust, low maintenance, and longlifetime highenergy laser systems for directed energy applications. Synchronized and passive phased pulsed laser array is built by intraactivity phase modulation. Osa 790 w incoherent beam combination of a tmdoped fiber. Highpower, highbrightness laser beam combining ieee photonics society laser workshop nov 7, 2012 t. Osa 790 w incoherent beam combination of a tmdoped.
Introduction to the issue on laser beam combining and. The term coherent beam combining also called coherent beam addition denotes one class of techniques within the more general technique of power scaling by beam combining. This servo system is based on entirely electronic components and consequently can be con. The 27 papers in this special issue focus on laser beam combining and fiber laser systems. Coherent combination of ultrafast fiber amplifiers iogs. Coherent beam combining of high power lasers coherent beam combining cbc is the holy grail of the laser industry, a long sought after technology enabling to electrooptically combine many channels of high power lasers without sacrificing beam quality.
A world leader in coherent beam combining of high power lasers. Output laser beam pumpbeam cross section of area a at focus rear facets front facet 808nm pump beam matched to the fiberoptic na, so no further slowaxis beam shaping is needed. Here we describe an active beam combining system used to coherently combine 21 semiconductor laser elements with an 81% beam combining efficiency in an external cavity configuration compared with. Incoherent combining of fiber lasers developed for. Opa technology enables ultrafast electro optical beam shaping, positioning and focusing. We demonstrate a scalable architecture for coherent combining of allfiber pulsed lasers with hybrid phase control involving passive phasing and active phasing for the first time. Techniques of coherent beam combining can be subdivided into. The major beam combining techniques can be broadly categorized into incoherent 8 and coherent 9 beam combining approaches. The result is an increase of power in the beam, without the increase of heat that would be generated by one beam to begin. T2 conference on lasers and electrooptics, cleo 2010. Typically, laserbased devices rely on a singleoutput system, where the laser is produced from a solitary source and then amplified through sophisticated optics.
Stimulated brillouin scattering phase conjugate mirror and. This tutorial explores the fundamental underpinnings of laser beam combining theory, as well as several incoherent and coherent beam combining methods. Cbc enables reaching very high laser power in single mode and also enables many other unique. In this beam combiner see figure, the laser diode outputs are collimated by aspherical lenses, then halfwave plates and polarizing beam splitters are used to com. Combine lasers to make a single strong beam physics forums. The use of lasers as illumination sources is a standard practice. High power handling, up to 12 kw, of mplc based shaper is.
The dynamic beam relies on civans propriety optical phased array opa technology. Wavelength beam combining for power and brightness. Coherent beam combining for high power laser applications. It describes the basic principles of such a generic phase locking process through the typical example of a michelson. Subsequent laser technology advances have allowed for practical implementations of those beam combining concepts, and beam combining. Coherent beam combining has been first implemented for cw lasers fan 2005. Coherent beam combining rp photonics consulting on laser. Coherent laser beam combining ebook by rakuten kobo. Usually, the term coherent addition applies to fiber lasers. Selfphasing is observed in this laser system, where we attribute the selfphasing behavior to the kramerskronig effect. One step further, coherent beam combining cbc also. Coherentbeamcombining forhighpowerlaserapplications. High power, high brightness lasers with diffraction limited beam quality have been sought since.
The arrangement used at aculight to spectrally beamcombine 1,400 diode laser emitters. The effect of polarization in passive coherent beam combining. This thesis is an effort to address several issues in coherent beam combining. Laser beam combining is currently seen as the primary route to high optical radiance in many laser systems.
Beam combining of quantum cascade laser arrays benjamin g. Subsequent laser technology advances have allowed for practical implementations of those beamcombining concepts, and beam combining. Coherent beam combining for high power laser applications by mercedeh khajavikhan abstract this thesis is an e. Beam profilers measure the spatial intensity distribution of a laser beam. Spectral beam combining also called wavelength beam combining or incoherent beam combining does not require mutual coherence, but rather uses emitters with nonoverlapping optical spectra.
Rp photonics encyclopedia beam combining, radiance. Chapter 4 application of oplls in coherent beam combining. In this beam combiner see figure, the laserdiode outputs are collimated by aspherical lenses, then halfwave plates and polarizing beam splitters are used to com. The single beams are then fed into a wavelengthsensitive beam combiner, such as a prism, a diffraction grating, a dichroic mirror, or a volume bragg. Lasers can be coherently combined by the technique of beam superposition using an optical element that overlaps the fields of two or more beams while simultane.
Stimulated brillouin scattering phase conjugate mirror and its application to coherent beam combined laser system producing a high energy, high power, high beam quality, and high repetition rate output. Modelocked pulses in passive coherent beam combining. Beam combining architectures incoherent sidebyside combining p out n x p 1 w l w l but same divergence. Coherent beam combining with multilevel optical phaselocked. In contrast, spectral beam combining sbc is a technique in which several individual beams with nonoverlapping optical spectra are combined to produce one highpower beam. N2 this tutorial explores the fundamental underpinnings of laser beam combining theory, as well as several incoherent and coherent beam combining methods.
Home products lasers laser diode modules obis lasers obis galaxy laser beam combiner obis galaxy laser beam combiner obis galaxy offers plugandplay as a laser beam combiner from the following input choices. Wav elength beam combining of quantum cascade laser arr ay s. As the ability of pumping andor cooling of a single laser is saturated, several similar lasers can be forced to oscillate in phase with common coupler. One step further, coherent beam combining cbc also helps to maintain the very unique properties of the laser emission with respect to. A typical, tactical architecture for the comparative evaluation of the key design issues for coherent beam combining cbc and incoherent beam combining ibc is shown in fig. Coherently combining a second 1w laser will result in a single 2w output and one 0w output. Restricted to repository staff only request a copy. It is expected that beamcombined laser systems will in the near future reach output power levels of tens to hundreds of kilowatts. There are also possibilities for longdistance freespace optical communications 1 and laserbased manufacturing. Coherent laser beam combining request pdf researchgate.
A homemade dammann grating is employed as a passive beamcombining optical element. Fan this work was sponsored by heljto under air force contract fa872105c0002. Coherent combining and phase locking of fiber lasers moti fridman, micha nixon, nir davidson and asher a. Linebeam systems stability and high depth of field to ensure a large process window short and long axis beam homogeneity for maximum throughput and beam utilization proven performance in leading largescale oled and lcd fabs line beam optical system 308 nm excimer laser annealing enables market growth of faster. An output power of 790 w is achieved from the signal combiner with a slope efficiency of 52. Passive and active fiber laser array beam combining. It covers the basics ranging from spectral beam combining to coherent beam combining. We experimentally demonstrate the importance of polarization on coherent beam combining efficiency as well as on. Modelocked pulses in passive coherent beam combining fiber. Current state of technology is summarized from this generic point of view, categorizing the specific approaches that exploit the various parameters or properties of light beam andor laser cavities. Key technologies like coherently combinable fiber laser, phase control of multiple beams and beam tilling are specially analyzed.
One step further, coherent beam combining cbc also helps to maintain the very unique properties of the laser emission with respect to its spectral and spatial properties. In this paper, we report on a highpower incoherent beam combination of three tmdoped fiber amplifiers at 1941 nm based on a 3. Comparison of coherent and incoherent laser beam combination. W is achieved from the signal combiner with a slope efficiency of 52. Pdf coherent beam combining is an attractive approach to scale up the power of fiber lasers which are limited by nonlinearities and thermal.
Coherent or incoherent beam combination of fiber lasers enables further scaling of the output power. Pdf allfiber coherent beam combining of fiber lasers. A beam splitter is simply a partially reflecting mirror, if you were orient the mirror so a laser reflected an individual beam 45 deg into the main beam path, you could combine the beam of different lasers since the main beam would then be passing through the mirrors in the transmission direction. A thesis submitted for partial fulfillment of the requirements. The concept of beam combining laser arrays to scale up in power with a diffractionlimited beam is an old one, with some pioneering work done at lincoln laboratory in the 1980s 1, 2.
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