We describe the technology areas of Q-Peak in terms of four categories, all related to solid state lasers.
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Diode-pumped lasers take advantage of advances in high-power semiconductor lasers, both pulsed and cw. We have developed a wide variety of diode-pumped lasers, including not only lasers based on Nd-doped crystals, but also lasers using other rare earths and Cr-doping.
Our initial research in diode-pumped lasers was directed towards development of single-frequency, Nd-doped lasers. In this we took advantage of the stable, low-heat-load pumping conditions afforded by diode pump sources compared to the more conventional lamp-pumped devices. The first lasers we made were unidirectional-ring, single-frequency designs end-pumped by 200-mW diode lasers, which were considered at the time to be "high power" devices. The frequency stability possible with diode pumping allowed us to demonstrate the first cw injection locking of two Nd:YAG lasers (DPL1). With the development of higher-power diode lasers we scaled our ring laser design to 0.6 W of power with a system design based on two 1-W diode-laser pumps. We added a galvanometer-controlled intracavity etalon to the laser to permit rapid tuning over 50 GHz in a time of less than 5 ms (DPL2). Our most powerful ring design to date has produced over 1 W of power using two 3-W diode pumps.
When high-power "bar" (linear array) lasers became commercial products we began to investigate their use in a variety of pumping schemes to generate multi-Watt cw power levels from solid state lasers. In order to develop a pump source for cw Ti:sapphire lasers we constructed, with NASA Langley SBIR funding, an end-pumped 1047-nm Nd:YLF laser that used a microlens array along with more conventional optics to focus the multiple beams from a 10-W bar into a small spot in the laser crystal (DPB1, click here for the complete paper). The laser produced nearly 4 W of multimode power and with an optimized resonator design generated 3 W of TEM00 output. With the addition of intracavity doubling via an LBO crystal we observed a total of 1.6 W of power at 523.5 nm. As fiber-coupled bars became commercially available we determined that they performed equally well, if not better than our microlens scheme, were much more compact and, potentially, were more robust. We have pumped a variety of systems with fiber-coupled bars, including Nd:YVO4 lasers at both 1064 and 1340 nm and, as we mention below, Tm,Ho:YLF lasers operating in the 2-um region.
Our next advance in high-power cw lasers (DPB2, click here for the complete paper) switched from an end-pumped to a side-pumped geometry and used two 20-W bars with a multi-pass Nd:YLF slab to generate 16 W of multimode power and over 13 W of TEM00-mode power with an M2 of less than 1.2. The pumping optics are simple, consisting of one cylinder lens per bar to collimate the widely diverging bar output beam. Repetitive Q-switching of the laser leads to peak powers exceeding 100 kW at kHz pulse rates. Our design is the basis for our patented Gain Module technology now being developed for industrial applications. Several efforts extended the performance of the bar-pumped Nd:YLF design through the use of an oscillator-amplifier architecture. The first oscillator-amplifier system was built as part of an Air Force SBIR program. Two papers (DPB3, DPB4, click here for the first and here for the second complete paper) describe how multiple amplifier designs have led to systems with cw power outputs in the 40-60 W range and repetitively Q-switched average powers of 30-50 W. Through injection seeding we have been able to obtain pulsed, Q-switched, single-frequency operation with 40 W of average power (DPB4). Through the use of 40-W bars, we have extended the power available from a single gain module to 25 W TEM00 (DPB5, click here for the complete paper) and 35 W multimode, and also greatly increased the peak power available in the Q-switched mode at high pulse rates (DPB6, click here for the complete paper.) With one amplifier following an oscillator, we can now generate over 50 W of 1047-nm power (DPB7, click here for the complete paper.)
One interesting development in the Nd:YLF Gain Module technology has been the generation of high-power, high-pulse rate mode-locked pulses, when amplifying the output of a SESAM-mode-locked Nd:YLF laser, and we have reported average powers as high as 15 W with 4.5-ps pulses at a 100 MHz rate (DPB6.)
The side-pumping technology has been extended to the Nd:YVO4 laser material with comparable 1064-nm cw powers to Nd:YLF and, in addition, high power output at 1342 nm (DPB8, click here for the complete paper). In a manner similar to Nd:YLF, we have used an oscillator-amplifier design to extend the 1064 and 1342-nm powers to record levels of >50 and >24 W, respectively (DPB9, click here for the complete paper.)
Other aspects of diode-pumped technology we have explored include the use of pulsed, rather than cw bars as pump sources. We have developed low-energy, short-pulse Nd:YAG lasers based on a simple and efficient, side-pumped "D-rod" design, where a curved surface on the laser material acts to collimate the diode output (DPP1, DPP2). This produces an excited region from which a large fraction of the available energy can be extracted in the TEM00 mode. Through the use of a passive, solid state Q-switch the D-rod laser can generate short (2.4 ns), mJ-level pulses (DPP3).
A significant activity of Q-Peak has been the exploration and development of diode-pumped lasers beyond traditional Nd-doped systems. Most of the effort has centered around 2-um-wavelength lasers based on Ho-doped, Tm-sensitized materials, and a large fraction of the early support came from the Geophysics Directorate of the Phillips Laboratory. Following on our development of diode-pumped, single-frequency Nd-doped lasers we worked to obtain single-frequency output from several different 2-um-wavelength laser materials, including Tm,Ho:YAG, Tm:YAG and Tm,Ho:YLF. The latter is currently our material of choice, for a variety of reasons including comparatively low levels of upconversion, relatively high gain and a low level of thermal lensing. With DARPA/NASA funding we have combined a fiber-coupled bar pump source and Tm,Ho:YLF to generate 4.5 W of CW, TEM00-mode power. With the addition of an acousto-optic Q-switch to the resonator we produced 6-mJ-energy pulses at a 100-Hz rate and 3-mJ pulses at 1 kHz (DPI1, click here for the complete paper). By changing the system to a unidirectional ring-cavity configuration we generated 2 W of single-frequency power at 2.06 um (DPI2, click here for the complete paper). In another approach to Tm,Ho:YLF lasers we have operated a liquid-nitrogen-cooled, D-rod laser pumped by pulsed diode arrays to produce over 50 mJ of pulsed energy (DPI3).
The longest-wavelength diode-pumped lasers that we have made to date are based on various Er-doped materials, and, with DARPA funding, we have produced cw power in the 2.79-2.94-um wavelength range. The pump sources were 970-nm diode lasers, and with two 1-W devices we generated a cw power of 0.5 W with the material Er:YSGG (DPI4, click here for the complete paper). More recently, with Air Force funding we have generated a record 1.8 W of cw power from Er:YLF at 2.81-um by using a side-pumped geometry (DPI5, click here for the complete paper.).
Microlasers are solid state lasers consisting of thin, parallel plates of end-pumped laser material, where the laser resonator is formed by the coated surfaces of the plates. Our contribution to microlaser technology had several components. The first was the development, with DARPA funding, of linear microlaser arrays pumped by diode bars, where we configured lasers doped with Nd, Tm-Ho and Er to operate in the 1-3 um wavelength range (DPM1, DPM2). Additional work on microlasers has included a joint effort with SDL, Inc. (San Jose, CA) to make two-dimensional, 3-um arrays (DPM3) and an effort with MIT Lincoln Laboratory (Lexington, MA) to demonstrate a 2-um laser based on Tm-doped YVO4 (DPM4).
In a system that combined microlaser technology with our bar-pumped devices, we used a passively Q-switched microlaser to generate 400-ps-long, low-energy pulses and then amplified the pulses with a side-pumped, Nd:YVO4 amplifier, to generate 335-uJ energies at a 2-kHz rate (DPM5, click here for the complete paper.) The effort was funded by a NASA Goddard SBIR program. As part of this effort, we observed some unique behavior of microlasers and developed a theory to explain our observations (DPM6, click here for the complete paper.)
CW, Single-Frequency Nd-Doped Lasers
DPL1. J. Harrison, G.A. Rines and P.F. Moulton, "Coherent Summation of Diode-Pumped Nd:YAG Ring Lasers," Opt. Lett. 13, 111 (1988).
CW, Bar-Pumped Lasers
DPB4. K. F. Wall, M. Jaspan, A. Dergachev, A. Szpak, J. H. Flint, and P. F. Moulton, "A 40-W, Single-Frequency, Nd:YLF Master Oscillator/Power Amplifier System," OSA Trends in Optics and Photonics Vol. 26, Advanced Solid State Lasers, Martin M. Fejer, Hagop Injeyan and Ursula Keller, eds. (Optical Society of America, Washington, DC 1999), pp. 216-221.
Pulsed Nd-Doped Lasers
DPP1. D. Welford, D.M. Rines, and B.J. Dinerman, "Efficient TEM00-mode Operation of a Laser-Diode-Side-Pumped Nd:YAG Laser," Optics Lett., 16, 1850 (1991).
Mid-IR Lasers
DPI1. A.Finch and J.H. Flint, "Diode-Pumped, 6-mJ, Repetitively Q-switched Tm, Ho:YLF Laser for Clear Air Turbulence Detection," in Conference on Lasers and Electro-Optics, 1995, OSA Technical Digest Series (Optical Society of America, Washington, DC 1995).
DPI5. A.Y. Dergachev, J.H. Flint and P.F. Moulton, "1.8-W CW Er:YLF Diode-Pumped Laser," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, Washington, DC, 2000), pp. 564-565.
Microlasers and Microlaser Arrays
DPM5. Y. Isyanaova, J.G. Manni, D. Welford, M. Jaspan, J. A. Russell, "High-Power, Passively Q-Switched Microlaser-Power Amplifier System," in Advanced Solid State Lasers, OSA Technical Digest (Optical Society of America, Washington DC, 2001) pp. 107-110.
DPM6. M.A. Jaspan, D. Welford, G. Xiao and M. Bass, "Atypical Behavior of Cr:YAG Passively Q-Switched Nd:YVO4 Microlasers at High-Pumping Rates," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, Washington, DC, 2000), p. 454.
The last two decades have seen the emergence of several new or improved nonlinear materials, and we have employed them in a number of ways to extend the functionality of solid state lasers. The materials include KTP and its isomorphs (such as KTA, RTA and CTA), which have become available in large crystal sizes suited for operation at high energies and average powers. Also included are BBO and LBO, materials first discovered in China, and CdSe, a semiconductor crystal improved in terms of optical loss through an Army-SBIR-funded collaborative effort between Q-Peak and Cleveland Crystals, Inc.
We have taken advantage of the large crystal size of flux-grown KTP to demonstrate the highest energy optical parametric oscillator (OPO) ever, a system driven by lamp-pumped, Q-switched Nd:YAG and Nd:YLF lasers. The signal output of the OPO falls in the 1500-nm wavelength region, making it well suited for eye-safe lidar systems (NLK1, click here for the complete paper). More recent published work on OPOs describes the highest-average power KTA OPO yet built, providing 33 W of eyesafe power in the 1530-nm wavelength region (NLK2, click here for the complete paper). Through the use of KTP OPOs we designed and assembled, under a NASA Langley Phase II SBIR, a complete, eye-safe LIDAR system for atmospheric studies, with some of the results reported at CLEO (NLK3).
For longer-wavelength generation we have utilized a Q-switched Cr,Er:YSGG laser to pump a CdSe OPO, resulting in the generation of signal wavelengths tuning from 3.6-4.2 um and idler wavelengths tuning from 8.3-12.6 um (NLO1, click here for the complete paper).
In later work, with support from the Air Force Research Laboratory (AFRL), we have developed the "Tandem OPO" system that uses an angle-tuned KTA OPO as a pump for a non-critically phase-matched, CdSe OPO, providing more power and greater flexibility than the Cr,Er:YSGG pump (NLO2, click here for the complete paper.) Development of the Tandem OPO started with the use of lamp-pumped Nd:YLF pump lasers to provide high-energy output and allowed demonstration of broadly tunable output from both KTA and CdSe OPOs (NLO3, click here for the complete paper.) With the lamp-pumped system, we developed single-frequency pump sources and used a tunable, external-cavity diode laser to injection-seed the KTA OPO, producing tunable, single-frequency output (NLO4, click here for the complete paper.) The design of the pump laser included a unique, image-rotation resonator (NLO5, click here for the complete paper.) Subsequently, we showed that new wavelengths could be generated by difference-frequency generation of the KTA OPO signal and idler beams and reported on the first operation of the Tandem OPO design with a diode-pumped, repetitively Q-switched, diode-pumped Nd:YLF laser (NLO6, click here for the complete paper.) The lamp-pumped efforts were supported by a Phase II SBIR from AFRL. Current development of the Tandem OPO involves the use of diode-pumped pump lasers.
We have combined nonlinear optics and the pulsed Ti:sapphire laser to generate both short and long wavelengths. We have obtained second-harmonic conversion into the wavelength range 340-470 nm with either BBO or LBO. Our efficiencies were as high as 60%; the highest energy was 250 mJ. Third and fourth-harmonic generation is also possible in BBO, with the short-wavelength end of 207 nm limited by the properties of BBO. In one NASA-sponsored program we examined the use of sum-frequency generation to extend the UV wavelength coverage down to 193 nm, using the crystal LBO. We developed a high-energy (40 mJ), single-frequency, third-harmonic source for wind-tunnel diagnostics in conjunction with Princeton University, with funding from a NASA Langley Phase II SBIR. For ozone detection we further developed third-harmonic Ti:sapphire lasers in the 308-315-nm region under another NASA Langley Phase II SBIR, using both BBO and LBO crystals, and set a record for efficient (35%) conversion of the laser to the third harmonic (NLT1, click here for the complete paper.)
In the direction of longer wavelengths, through the use of KTP and KTP-isomorph OPOs pumped by pulsed Ti:sapphire lasers we have generated wavelengths in the 1000-3000 nm region. The arrangement takes advantage of non-critical phase-matching and tuning of the pump wavelength to simplify the OPO design (NLT2, click here for the complete paper.) An extension of this concept, funded by an Air Force Phase II SBIR program, has involved a high-pulse-rate Ti:sapphire pump laser, pumped by a diode-pumped, repetitively Q-switched Nd:YLF laser, to generate pulsed, tunable energy from 1500-2500 nm at a 10-kHz rate (NLT3, click here for a Powerpoint presentation.)
We have summarized much of our initial work with Ti:sapphire lasers and nonlinear optics in a review article (NLT4).
We have combined our high-power diode-pumped Nd:YLF Gain Module laser technology with harmonic generation to produce record levels of high-pulse-rate average power in the UV, at 262 and 209 nm (NLD1, click here for the complete paper). The technology was subsequently employed by our research partner, Ushio Corporation, to demonstrate 1 W of average power at 196.3 nm at a 5-kHz rate, through the use of sum-frequency generation in CLBO crystals (NLD2.)
Another application of the Nd:YLF laser technology has been as a driver for our patented RGB OPO, a nonlinear device that converts high-power green energy to red and blue wavelengths suited for color projection systems. A recent summary of the system (NLD3, click here for a Powerpoint presentation) shows that we have been able to generate over 15 W of red, green and blue power at a 22 kHz rate.
Nonlinear Conversion in KTP and Isomorphs
NLK3. R.A. Schwarz, A. Finch, D. Welford, P.F. Moulton and G.A. Rines, "Development of Advanced Solid State Lasers for Lidar," in Conference on Lasers and Electro-Optics, Vol. 11, 1997 OSA Technical Digest Series (Optical Society of America, Washington, DC, 1997) pp. 406-407.
Long-wavelength OPOs
Ti:sapphire-Driven Systems
NLT1. A. Y. Dergachev, B. Pati and P.F. Moulton, "Efiicient Third-Harmonic Generation with a Ti:sapphire Laser," OSA Trends in Optics and Photonics Vol. 26, Advanced Solid State Lasers, Martin M. Fejer, Hagop Injeyan and Ursula Keller, eds. (Optical Society of America, Washington, DC 1999), pp. 96-99.
NLT3. A Zavriyev, K.F. Wall and P.F. Moulton, "A Broadly Tunable, All-Solid-State, Near-IR Source," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, Washington, DC, 1999), p. 420.
DPSSL-driven Systems
Most of our work on tunable solid state lasers has concentrated on the Ti:sapphire system, because of its versatility, wide tuning range (approximately 680-1100 nm) and power-output capacity. We have been at the forefront in the development of cw lasers pumped by argon-ion gas lasers or frequency-doubled Nd-doped solid state lasers, and pulsed lasers pumped by frequency doubled, Q-switched, Nd-doped lasers. Dr. Peter Moulton, Chief Technology Officer of Q-Peak has a special interest in Ti:sapphire, since he was first to demonstrate laser action from the material in 1982, while he was at MIT Lincoln Laboratory (Ti1). He is shown below, examining one of the early samples of material grown for laser operation
In the area of pulsed lasers, we have developed high-brightness, gain-switched Ti:sapphire lasers pumped by the second harmonic of Q-switched Nd-doped lasers. Our research in this area was first supported by NASA Langley Research Center, for application to laser-based atmospheric remote sensing. Since 1995, NASA has flown a system based on our original design in the LASE Program. High points of our work include pulse energies exceeding 400 mJ at wavelengths ranging from 720-920 nm. We have obtained outputs near the diffraction and transform limits through the use of unstable-resonator technology and injection seeding (Ti2, Ti3, Ti4) and have patented the basic laser design. Our most recent work has involved the use of Ti:sapphire lasers to drive a variety of nonlinear processes, including harmonic generation and parametric oscillators, as described in the section above on Nonlinear Optics.
The commercial results of our cw laser development were the Titan-CW, Titan-QS and Titan-ML products, winners of a number of awards from trade publications such as Photonics Spectra. The Titan-CW device was made available as a standard cw source utilizing a standing-wave resonator or as a single-frequency ring laser for applications where high spectral purity is required. The patented (P1) "swing resonator" design developed by James Harrison allowed easy conversion between standing-wave and ring configurations. Our design allowed operation with very low pump powers, and as a result we were the first to demonstrate a truly all-solid-state cw Ti:sapphire laser pumped by a diode-pumped, frequency-doubled Nd-doped laser (Ti5). In later NASA-sponsored work we operated a single-frequency ring Ti:sapphire laser with a diode-pumped laser, as a possible tunable seeding source for high-energy pulsed lasers (DPB1, click here for the complete paper). We have reviewed the tuning techniques and frequency-stability properties of cw Ti:sapphire lasers in two successive publications (Ti6, Ti7). The Titan-ML product was a femtosecond-pulse mode-locked version of the Titan-CW, one of the first commercial systems, and a winner of the Lasers and Optronics "Top Ten Products of 1991." Another variation of the Titan-CW was the Titan-QS product, which allowed generation of tunable-wavelength, short pulses at pulses rates as high as 500 kHz (Ti8, click here for the complete paper). As the technology of diode-pumped solid state lasers has improved the ion-laser pump sources formerly used have been replaced by all-solid state pumps.
References:
Ti1. P.F. Moulton, "Spectroscopic and Laser Characteristics of Ti:Al2O3", JOSA B3, 125 (1986).
Ti2. G.A. Rines, P.F. Moulton and J. Harrison, "Narrowband, High-Energy Ti:Al2O3 Lidar Transmitter for Spacecraft Sensing," in Tunable Solid State Lasers, Vol. 5 of the OSA Proceedings Series, M.L. Shand and H.P. Jenssen, eds. . (Optical Society of America, Washington, DC 1989), pp. 2-8.
Ti3. G.A. Rines and P.F. Moulton, "Performance of Gain-switched Ti:Al2O3 Unstable-Resonator Lasers," Opt. Lett. 15, 434 (1990).
We were the first to demonstrate and analyze room-temperature operation of the Co:MgF2 laser (Co1, Co2), which generates energy in the IR wavelength range 1750-2500 nm when pumped by a 1320-nm Nd:YAG laser. As part of a NASA program we grew laser-quality material at our facility and commercialized the room-temperature laser. The commercial product was one of Laser and Optronics "Top Ten Products of 1989." In later work we scaled the energy level of the device to 900 mJ/pulse (Co3).
We have investigated the potential of a new laser material Cr:LiSAF, first developed by Payne et al. at Lawrence Livermore National Laboratory. Providing similar wavelength coverage to the Ti:sapphire laser, from 780 to beyond 1000 nm, the Cr:LiSAF laser can be pumped directly by conventional flashlamp technology, similar to that used for Nd-doped lasers. In contrast, flashlamp pumping of Ti:sapphire requires the use of special short-pulse lamps, high voltages and thyratron drivers. We have demonstrated, with NIH funding, a high-brightness Cr:LiSAF oscillator-amplifier system capable of near-diffraction-limited output at the 400-mJ level, at wavelengths around 860 nm, and have frequency doubled the output with 50% efficiency. In preliminary experiments we have extended the Cr:LiSAF output into the UV via fourth-harmonic generation, and observed 25 mJ of energy at 215 nm (Cr1, click here for the complete paper).
It is possible to operate the Cr:LiSAF laser in the cw mode with the use of diode-laser pump sources in the 680-nm region. In one program, also with NIH funding, we operated the first single-frequency ring Cr:LiSAF laser to provide tunable, narrow-linewidth output in the 850-nm region (Cr2, click here for the complete paper).
Cr:YAG is a unique laser material in providing tunable output in the fiber telecommunications band around 1500 nm. In a recent, Department of Commerce Phase II SBIR we developed the first tunable, single-frequency Cr:YAG laser, and generated output from 1332 to 1554 nm, with as much as 680 mW of power (Cry1, click here for a complete paper.) The Cr:YAG crystal was pumped by one of our high-power Nd:YLF lasers.
P.F. Moulton of Q-Peak reviewed the general area of tunable solid state lasers in 1992 and the article (TL1), although lacking in data on the latest advances, has some basic discussions that may be of interest.
References:
Co:MgF2
Cr:LiSAF
Cr1. H.H. Zenzie and Y. Isyanova,"High-energy, High-efficiency Harmonic Generation from a Cr:LiSrAlF6 Laser System,,"Opt. Lett. 20, 169 (1995).
Cr2. H.H. Zenzie, A. Finch and P.F. Moulton, "Diode-Pumped, Single-Frequency Cr:LiSrAlF6 Ring Laser," Opt. Lett. 20, 2207 (1995).
Cr:YAG
Cry1. D. Welford and M.A. Jaspan, "Single-Frequency Operation of a Cr:YAG Laser from 1332 nm to 1554 nm," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, Washington, DC, 2000), pp. 435-436.
General
TL1. P.F. Moulton, "Tunable Solid State Lasers," Proc. IEEE 80, 348 (1992)
Although diode pumping represents the future of technology for solid state lasers, in systems requiring high pulsed energies the cost of diode lasers presently makes them impractical for applications other than space-based or military-critical. Our work on lamp-pumped lasers has involved study and development of unique and innovative pulsed systems, involving either new laser materials, new operating modes or both. Much of our work was based on materials development first carried out in the Former Soviet Union in the 1980's, relating to Cr-sensitized garnet materials. In addition, we have advanced the design of lamp-pumped lasers for particular applications, such as the pumping of pulsed Ti:sapphire lasers. As an example, we studied the generation of microsecond-duration sources that might be better suited for Ti:sapphire pumping than the more conventional nanosecond Q-switched lasers (LP1, LP2). In the area of new laser materials, we operated the first slab-geometry lasers based on the materials Nd,Cr:GSGG (LP3) and Cr,Tm,Ho:YAG (LP4).
We have developed and commercialized a number of mid-IR lamp-pumped laser materials, including the 3-um lasers Er:YAG, and Cr,Er:YSGG (LP5) and the 2-um lasers Tm:YAG, Cr,Tm,Ho:YSGG and Cr,Tm,Ho:YAG (LP6). The vehicle for commercialization was the Laser 1-2-3 system formerly manufactured and sold by SEO.
Recently we have engineered a robust and compact lamp-pumped, Q-switched Nd:YAG/YLF laser head suited for field applications such as lidar. The oscillator-amplifier configuration produces energy levels as high as 800 mJ from a package the size of a shoebox, and has been incorporated into several custom laser systems. The CLH page includes more details on the compact laser head.
Microsecond-Pulsewidth Sources
LP1. J. Harrison, G.A. Rines and P.F. Moulton, "Long-Pulse Generation with a Stable-Relaxation-Oscillation Nd:YLF Laser," Opt. Lett. 13, 309 (1988).
LP2. J. Harrison, G.A. Rines and P.F. Moulton, "Stable Relaxation Oscillation Nd Lasers for Long-pulse Generation," IEEE J. Quantum Electron. 24, 1181 (1988).
Slab Lasers
LP4. D.M. Rines, J.H. Flint and P.F. Moulton, "Characterization of a Cr,Tm,Ho:YAG Slab Laser", in Advanced Solid State Lasers,1991 Technical Digest Series (Optical Society of America, Washington, DC 1991) pp. 115-117.
Mid-IR Lasers
LP5. P.F. Moulton, J.G. Manni and G.A. Rines, "Spectroscopic and Laser Characteristics of Er,Cr:YSGG," IEEE J. Quantum Electron. 24, 960 (1988).
LP6. P.F. Moulton, E. Adamkiewicz and S. Wright, "Holmium Laser Cuts into Medical Applications," Laser Focus World, 28, March, 1992, pp. 65-69.
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