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We have measured and characterized, over a wide range of doping levels, the UV-near-IR (190-2000-nm) absorption properties of Ti:sapphire crystals. We find that the strengths of absorption centered around 400-450 and 268 nm depend on the square of the Ti3+ doping level, suggesting an origin from pairs of Ti3+ ions. In addition, we have identified an absorption feature below 210 nm due to Ti3+, rather than Ti4+ charge-transfer transitions. Finally, our data on 800-nm-peak, near-IR absorption shows a complex lineshape, with a lower limit set by Ti3+ pair absorption. Thus the maximum possible Figure-of-Merit for Ti:sapphire reduces as the doping level increases.

The development of higher-power InGaN-based diode lasers facilitates their application to optical pumping of Ti:sapphire lasers. Recent diode-pumping results highlight some unexpected behavior, specifically with 450-nm-wavelength devices. To better understand this we have measured and characterized, over a wide range of doping levels, the absorption properties of Ti:sapphire crystals. We find significant changes in the spectral shape of the pumping band in Ti:sapphire with increased doping, and explain the results in terms of absorption due to pairs of Ti3+ ions. Our subsequent discussion attempts to explain prior data, and also provides guidance on optimizing designs for InGaN-diode-pumped Ti:sapphire lasers.

We report on the development of an all-fiber, 68-kW-peak-power, 16-ps-pulse-width, narrow-bandwidth, linearly polarized, 1064-nm fiber laser suitable for high-power, picosecond-pulse-width, green-light generation. Our 1064-nm fiber laser delivered an average power of up to 110 W at a repetition of 100- MHz in a narrow bandwidth, with minimal nonlinear distortion. We developed a high-power, picosecond green source at 532 nm through use of single-pass frequency-doubling of our 1064-nm fiber laser in lithium triborate (LBO). Using a 15-mm long LBO crystal, we have generated 30 W of average power in the second harmonic with 73-W of fundamental average power, for a conversion efficiency of 41%.

We report here on the performance of a narrow-line, mid-IR source based on a PPLN-crystal optical parametric generator (OPG). The crystal was pumped by a pulsed, 20-MHz-rate, 1064-nm Yb:fiber-based source operating with 20- psec pulses. The OPG produced a broad spectrum between 2027 nm and 2239 nm. By placing a band-pass filter after the OPG we were able to select a 30-nm bandwidth output, and we achieved further line reduction (0.7 nm) and 4.5 mW of average power at 2039 nm, using a reflective Volume Bragg Grating (VBG). Devices such as piezo-controlled etalons can provide rapidly tunable, narrow-linewidth power from this system.

We describe fundamental measurements of the properties of thulium (Tm)-doped silica and power scaling studies of fiber lasers based on the material. Data on the high-lying Tm:silica energy levels, the first taken to our knowledge, indicate that pumping at 790 nm is unlikely to lead to fiber darkening via multiphoton excitation. Measurement of the cross-relaxation dynamics produces an estimate that, at the doping levels used, as much as 80% of the decay of the Tm level pumped is due to cross relaxation. Using a fiber having a 25-mum-diameter, 0.08 numerical aperture (NA) core, we observed fiber laser efficiencies as high as 64.5% and output powers of 300 W (around 2040 nm) for 500 W of launched pump power, with a nearly diffraction-limited beam. At these efficiencies, the cross-relaxation process was producing 1.8 laser photons per pump photon. We generated 885 W from a multimode laser using a 35-mum, 0.2-NA core fiber and set a new record for Tm-doped fiber laser continuous-wave power.

We have developed a quasi-CW, deep ultraviolet source producing >250 mW of 205-nm radiation. The source consists of a 100-MHz, mode-locked, 15-W, 1047-nm master-oscillator/power-amplifier, a synchronously pumped optical parametric oscillator, and three nonlinear conversion stages.

We have operated, for the first time to our knowledge, a directly diode-pumped Cr:ZnSe femtosecond oscillator. In addition, we have constructed a CPA Cr:ZnSe-based ultrafast laser system that generates 2475-nm, 1-kHz-rate, 1 GW -peak-power pulses.

Reported near-diffraction-limited, cw power levels from Tm-doped silica fiber lasers in the 2000-nm wavelength region have now passed the 1 kW level, due to advances in fiber technology, pump lasers and associated pump-coupling fiber optics. Compared to the more common high-power Yb-doped fibers, Tm:silica fibers have several advantages, particularly with respect to limits set by fiber nonlinear effects such as stimulated Brillouin scattering. These have been exploited to allow generation of 600 W of single-frequency, narrow-linewidth power, the most, to our knowledge, of any fiber-based laser. In addition, there have been significant advances in generation of high-peak-power pulses from Tm:fiber-based sources.

We review the use of Ti:sapphire lasers to produce blue laser sources with particular emphasis on wavelengths useful for underwater communications. We discuss past designs as well as future prospects.

Pump wavelengths of less than 460nm compromise the performance of Ti:sapphire lasers by inducing loss. This – and not pump brightness or absorption – is the primary performance limitation in these lasers.

We report a 0.8-5.0 ns-width, 0.1-2 MHz-rate Nd-MOPA laser passively Q-switched with a semiconductor saturable Bragg reflector producing 7.5 W of average power at 532 nm in a diffraction limited beam.

We report 62% and 56% SHG conversion efficiency in generating 532-nm using MgO-doped and undoped PPSLT crystals, respectively. We compare SHG obtained using both materials and discuss their suitability for the generation of Watt-level green-radiation.

2-mJ, 600-fs, 1047-nm pulses at a 250-Hz rate from a compact, Yb -doped crystal CPA laser system were achieved. We combine a positive-dispersion-regime oscillator, regenerative amplifier and a hybrid stretcher/compressor based on chirped volume Bragg gratings.

A high-power, actively modelocked, cryogenically cooled Yb:YAG laser has been demonstrated. At a repetition rate of 80 MHz, 214-ps pulses with 55 W of output power have been measured.

Over 600 mW has been obtained from a single-frequency Nd:YAG ring laser pumped by two 1-W diode lasers. Tuning over 60 GHz in less than 5 ms was achieved with a galvanometer-controlled intracavity etalon. Locking to an external reference cavity has also been demonstrated. >

We report the development of a tunable, diode-pumped Cr:LiSrAlF 6 ring laser that emits as much as 43 mW of power in a single longitudinal mode at 849 nm. By tuning the output with a birefringent filter, we achieved single-frequency operation from 810 to 860 nm. The short-term (10-s) frequency stability was better than 15 MHz.

A binary grating has been used to achieve coherent summation of diode-laser-pumped Nd:YAG ring lasers operating at 1.06 μm. Mutual coherence of two such devices was achieved by optical injection locking. This is believed to be the first demonstration of cw injection locking of solid-state lasers other than semiconductor diode lasers. By combining two beams, an efficiency of 75% (92% of the theoretical limit) has been demonstrated in a configuration that could be used to combine a large number of individual lasers.

We have developed a compact, efficient, passively Q-switched, solid-state-laser, producing 7-mJ, < 10 ns pulses, and a near TEM00 beam. The cross section of the laser crystal was D-shaped and it was side pumped.

We discuss several classes of tunable solid state lasers, based on Yb-doped crystals, Tm-doped fibers and Cr:ZnSe crystals, and patterned semiconductor nonlinear materials, all of which show promise for applications to analytic sensors.

Using noncritically phase-matched 1-cm(2) -aperture KTiOAsO(4) (KTA) crystals in an optical parametric oscillator (OPO), we have demonstrated a sustained average signal power of 33 W at 1534.7 nm. To our knowledge, this is the highest-average-power signal ever generated by an OPO. The pump source was a 100-Hz Q -switched 1064-nm Nd:YAG laser. Compared with that of the similar and more-common material KTiOPO>(4) , idler absorption in KTA is negligible, allowing high-power operation with minimal thermally induced refractive distortion in the OPO crystal.

Using a side-pumping geometry, we obtained 400 W of cw power with 56% optical-to-optical efficiency from a cryogenically-cooled, Yb:YAG laser. In Q-switched operation, we obtained 200 W with a near diffraction limited beam.

We report on a Tm-doped silica fiber laser that generates 263 W of cw power with a launched pump conversion efficiency of 52% and a slope efficiency of 59%.

We report an efficient, TEM00, Tm:fiber-laser-pumped, Ho:YLF laser producing 43 W cw power and 45 mJ of pulse energy in the Q-switched regime, the highest values yet reported for this material.

A compact long-wavelength infrared (LWIR) source, based on the combination of a high-pulse-rate, 1-μm-wavelength solid-state laser with rapid and broadly tunable tandem optical parametric oscillators (OPOs) was demonstrated. Nanosecond pulses with up to 100 μJ energy, tunable within the 8-11 μm LWIR range were achieved.

In this paper we describe the design and performance characteristics of a diode-laser-pumped, cw, NdrYLF laser with intracavity second harmonic generation (SHG). We include descriptions of the micro-optics used to couple pump power from a 10-W diode laser to the Nd:YLF crystal in an end-pumped configuration; the opto-mechanical design of the Nd:YLF gain element; the performance of the Nd:YLF laser at 1047 nm; and the design and performance of resonators configured for intracavity SHG with both KTP (II) and LBO (I) crystals. The highest output power obtained to date, with an LBO SHG crystal, was 1.25 W at 523.5 nm.

We report a diode-pumped, Nd:YLF, Q-switched, short-pulse, 30-100-kHz MOPA system producing, to our knowledge, the highest third- and fourth-harmonic powers (25 and 10 W, respectively) yet reported for high-pulse-rate Nd-doped lasers.

This paper reports on the design and performance of a satellite-ranging transmitter consisting of a Cr:YAG passively Q-switched Nd:YAG microlaser and an air-cooled Nd:YVO4 power amplifier, generating 235-µJ, 270-ps pulses at a 2-kHz rate.

We have recently demonstrated efficient operation of KTP optical parametric oscillators (OPO) pumped by multimode Nd:YLF and Nd:YAG lasers. These experiments have demonstrated what is, to our knowledge, the highest pulse energy (450 mJ) and the highest average-power signal output (7.4 W) obtained to date from an OPO. With a 1.1-J, 10-Hz, Nd:YAG pump laser we obtained 450 mJ (4.5 W) of signal output at 1571 nm from a singly-resonant OPO. In a separate experiment with a 625-mJ, 30-Hz, Nd:YLF pump laser we obtained 7.4 W (245 mJ, 30 Hz) of signal output at 1550 nm. These results provide a clear demonstration that very high pump-to-signal energy conversion (up to 41%) can be obtained from an OPO even with highly multi-transverse-mode pump lasers.

We report on several developments in solid state lasers and nonlinear optics specifically for applications in remote sensing. In the area of UV sources for ozone monitoring, we have developed an efficient, third-harmonic, tunable Ti:sapphire-laser-based source. For long-range, eyesafe detection of aerosols, we report a high-energy optical parametric oscillator (OPO) driven by a flashlamp-pumped, Q-switched Nd:YLF laser. Finally, for mid-infrared DIAL, we have developed a Tandem-OPO that converts a common Nd-doped laser into a tunable source capable of providing wavelengths in the range 1500-5500 nm and 8000-12000 nm.

We report an energy of 110 mJ per pulse from a diode-pumped, double-pulse, Q-switched, conduction-cooled, 1053-nm, Nd:YLF laser designed for space-based applications. We obtained a slope efficiency of 23% and used heat pipes for laser-head cooling.

We report an efficient, TEM00, Tm:YLF-pumped Ho:YLF laser system producing 21 W CW power and 37 mJ of pulse energy in the Q-switched regime, the highest values yet reported for this material. A ZGP OPO pumped by the Ho:YLF laser produced pulse energies above 10 mJ at 50-400 Hz.

We report a 4-W, 2810-nm, diode-pumped, cw Er:YLF laser, to the best of our knowledge the highest power yet achieved for a cw Er-doped laser operating on the 4I11/2 - 4I13/2 transition. We tuned the laser on 11 different lines in the 2720-2840-nm region.

We report a diode side-pumped, single-stage, multi-pass Yb:S-FAP amplifier designed to achieve high pump brightness, uniform absorption, and high amplification. We demonstrate highly efficient operation of the amplifier with an input signal from a Nd:YLF oscillator.

A quasi-cw, deep ultraviolet source has been developed, producing >200 mW of 205-nm radiation. The source consists of a mode-locked 16-W 1047-nm master-oscillator/power- amplifier, a synchronously-pumped optical parametric oscillator, and three non-linear conversion stages.

We report on a broadly tunable (1905 - 2067 nm) diode-pumped Tm: YLF laser producing cw output powers of >18 W (37% slope efficiency) in multimode operation and 12 W in the TEM00 mode.

The first demonstration of cw operation of a side-diode-pumped, 1047-nm Yb:S-FAP laser is reported. The output power achieved was 3 W, which represents, to our knowledge, the highest cw power yet reported from Yb:S-FAP.

In this paper we discuss our red, green, and blue (RGB) optical parametric oscillator (OPO) based laser projection display. The complete project display consists of two subsystems, the RGB-OPO laser head and the light modulation unit. The RGB lights from rack-mounted laser head are fibers coupled to the projection unit for independent placement. The light source consists of a diode-pumped pump laser and a LBO-based OPO. Based on our Nd:YLF gain module design, the pump laser is frequency doubled to serve as the pump source for the OPO. The unconverted pump power is recycled as the green light for projection. The singly resonant, non- critically phase-matched (NCPM) OPO has, to date, generated 13 W of 898-nm signal power and an estimated 9.3 W of intra- cavity idler power at 1256 nm. With approximately 76% of pump depletion, the power of the residual green light for projection is about 5.8 W. We have extra-cavity doubled the signal to produce approximately 3.5 W of 449-nm blue light and intra-cavity doubled the idler to produce approximately 6 W of 628-nm red light. The OPO-based RGB source generates about 4000 lumens of D65-balanced white light. The overall electrical power on a commercially available JVC's three- panel D-ILA (reflective LCD) projector with the arc-lamp removed and extensive modifications. The projector has a native resolution of 1365 x 1024 and the expected on screen lumens from our laser display is about 1200 lumens.

In this paper we discuss our red, green, and blue (RGB) optical parametric oscillator (OPO) light source for projection display applications. Our source consists of a diode-pumped pump laser and a LBO-based OPO. Based on our Nd:YLF gain-module design, the pump laser is frequency doubled to serve as the pump source for the OPO. The unconverted pump power is recycled as the green light for projection. The singly resonant, non-critically phase- matched OPO has, to date, generated 13 W of 898-nm signal power and an estimated 9.3 W of intra-cavity idler power at 1256 nm. With approximately 76% of pump depletion, the power of the residual green light for projection is about 5.8 W. We have extra-cavity doubled the signal to produce approximately 3.5 W of 449-nm blue light and intra-cavity doubled the idler to produce approximately 6 W of 628-nm red light. The OPO-based RGB source generates about 4000 lumens of D65-balanced white light. The overall electrical power luminous efficiency (diodes only) is about 14.6 lumens/Watt.

We report the highest efficiency (to the best of our knowledge) third-harmonic generation from a gain-switched Ti:sapphire laser. Using Type I LBO crystals, we obtained ~45 % conversion in the sum-frequency stage and ~35% overall conversion from the fundamental. The diode-laser-injection-seeded Ti:sapphire laser operated in 920-960 nm range to provide 307-320-nm UV energy.

We report on the operation of a high beam quality (M2 < 1.2), 40-W, single-frequency, Q-switched Nd:YLF master-oscillator/power-amplifier system based upon transversely-pumped Nd:YLF gain modules.

A systematic investigation of the tunability and efficiency of non-critically phase-matched (NCPM) and critically phase-matched (CPM) KTA OPOs using x- and y-cut crystals orientations has been conducted for the first time. Using our previously developed tandem, KTA-CdSe, OPO technology, we demonstrate a multi-wavelength, mid-infrared source capable of simultaneously delivering tunable radiation in four broad bands covering the range from 11.5 to 10 µm with high conversion efficiency.

A compact and efficient laser source is required as an enabling technology for laser projection displays. We discuss a scalable green-pumped, non-critically phase- matched LBO optical parametric oscillator (OPO) which simultaneously generates red and blue wavelengths that are ideal for display applications. Pumping the OPO with 9.7 W of 523 nm green light from a frequency-doubled, diode-pumped Nd:YLF oscillator/amplifier laser system has resulted in a measured 4.0 W of 896 nm signal power and an estimated idler power of 2.8 W. The signal was extra-cavity frequency doubled to produce 1.10 W of blue light at 448 nm. Intra- cavity frequency doubling of the idler produced 1.95 W of red light at 628 nm.

Summary form only given. The main objective of this work is to achieve high cw output in the 3-/spl mu/m wavelength range from a solid state laser. As it was shown in previously published papers, Er:LiYF/sub 4/ (Er:YLF) is an efficient 3-/spl mu/m material suitable for laser diode pumping. In the present work we have developed a cw Er:YLF laser based on an Er:LiYF/sub 4/ slab sidepumped by two diode laser bars. The side pumped slab design has the potential to scale to much higher power than end-pumped configurations.

Using a side-pumped, Nd:YLF slab laser design, we have obtained a TEM00- mode output power of 25.7 W with 43.5% optical efficiency and a multimode output of nearly 36 W with 46% efficiency. As an amplifier of a SESAM-mode-locked laser, the same design has allowed us to generate, with 4.5-ps pulses at a 100-MHz rate, 15.7 W of average power in the fundamental and 2.9 W of power at the fourth harmonic.

The efficiency of multi-watt ultraviolet radiation generation by harmonics processes in β-BaB2O4 (BBO) can be improved by reducing thermal dephasing. The dephasing arises from local heating of BBO by the linear absorption of green (second harmonic) and ultraviolet (fourth harmonic) radiation by crystal defects that are induced by two-photon absorption of high peak power ultraviolet radiation. Such absorption can be reduced by decreasing the repetition rate to ∼1 kHz to allow the defects to decay between the laser pulses and/or heating BBO crystal to 150–200 °C to increase the decay rate of the induced defects.

We address the critical issue of thermal dephasing of the UV harmonic generation process due to nonlinear absorption in Li2B4O7 crystals. Reduction of nonlinear absorption is achieved by increasing the crystal temperature up to 200 °C and reducing the pulse repetition rate. Our results show the way for significant improvement of the conversion efficiency for the fourth harmonic generation of Nd lasers using Li2B4O7 crystals.

In this paper we will describe the most recent advances in the development of Ti:Al2O3, unstable-resonator lasers. Results include demonstration of improved long-wavelength operation and efficient second, third and fourth harmonic generation. Second harmonic generation (SHG) results will be described for three nonlinear crystals: deuterated potassium di-hydrogen phosphate (D-KDP), beta barium borate (BBO) and lithium triborate (LBO). Third harmonic generation (THG) in BBO and D-KDP will be presented along with fourth harmonic generation (FHG) data obtained with BBO crystals.

We have demonstrated cw laser operation at wavelengths near 3 microm from monolithic, Er-doped YSGG, GGG, and YAG lasers by direct upper-state pumping in the 0.97-microm wavelength region with either a Ti:sapphire laser or InGaAs diode lasers. We have obtained slope efficiencies as high as 31% and, with diode-laser pumping, output powers of 0.5 W. In addition, we have demonstrated tunable single-frequency operations from Er:YAG.

A cw Ti:A1(2)O(3) ring laser with a threshold power of 119 mW is demonstrated. It provides a tunable source of single-frequency, diffraction-limited radiation that is suitable for injection seeding. The Ti:A1(2)O(3) laser is operated with a diode-laser-pumped, frequency-doubled, Nd:YAG laser as the sole pump source.