Efficient resonantly-clad-pumped laser based on a Er:YAG-core planar waveguide.

We demonstrated continuous wave operation of an in-band pumped Er:YAG planar waveguide laser with the output of 75 W at 1645 nm and a slope efficiency of 64% with respect to the absorbed pump power at 1532 nm.

Resonantly pumped single-mode channel waveguide Er:YAG laser with nearly quantum defect limited efficiency.

We demonstrated the continuous-wave operation of a resonantly pumped Er:YAG single-mode channel waveguide laser with diffraction-limited output and nearly quantum defect limited efficiency. Using a longitudinally core-pumped, nearly square (61.2 µm×61.6 µm) Er3+:YAG waveguide embedded in an undoped YAG cladding, an output power of 9.1 W with a slope efficiency of 92.8% (versus absorbed pump power) has been obtained. To the best of our knowledge, this optical-to-optical efficiency is the highest ever demonstrated for a channel waveguide laser.

Acousto-optically Q-switched, resonantly pumped, Er:YVO4 laser.

We report on the performance of an acousto-optically Q-switched Er:YVO4 laser resonantly pumped in the 4I 15/2 → 4I 13/2 transition. The laser output was π-polarized at 1603 nm. It operated with a 1-40 kHz pulse repetition rate (PRR) and delivered up to 1.15 W of average output power. A slope efficiency of 45% with respect to the absorbed pump power was demonstrated at the pulse repetition rates of 10 kHz and above. The best Q-switched operation with 470 µJ, 50 ns long pulses was achieved at the PRR of 1-2 kHz and pumping with a fiber-coupled laser diode. This Q-switched pulse energy is the highest reported for Er:YVO4 single crystal laser.

High efficiency, resonantly diode pumped, double-clad, Er:YAG-core, waveguide laser.

We report on the highly efficient, resonantly diode-pumped Er:YAG-core, double-clad, all-crystalline eye-safe waveguide laser. A 500 × 500 µm Er(3+)(1%):YAG single-crystalline core with an ultra low numerical aperture (NA) of ~0.02 was surrounded by a 700 × 700 µm undoped single-crystalline YAG cladding. The entire Er:YAG/YAG core/clad structure was over-clad by transparent magnesium aluminum spinel (MgAl(2)O(4)) ceramic. The waveguide was continuously (CW) clad-pumped by a spectrally-narrowed, fiber-coupled InGaAsP/InP laser diode module at ~1532 nm. We achieved 25.4 W of output power at 1645 nm with a beam quality of M2 ~2.6. The achieved 56.6% slope efficiency with respect to the absorbed pump was derived by factoring out scattering loss of the pump light in the inner cladding. With a wavelength-selective cavity, the waveguide laser delivered ~8 W of output power at 1616.6 nm. To the best of our knowledge, it is the first reported laser experiment with a crystalline Er(3+):YAG-core and a truly double-clad crystalline waveguide structure.

Highly efficient dual-wavelength laser operation of cryo-cooled resonantly (in-band) pumped Ho3+:YVO4 laser.

We have demonstrated a CW, multiwatt, dual-wavelength cryogenically cooled, resonantly (in-band) pumped Ho(3+):YVO(4) laser with nearly quantum-defect-limited performance. The Ho(3+)(2%):YVO(4) gain element, which was maintained at ~80 K and pumped by a Tm-fiber laser at 1966 nm, emitted at wavelengths of either 2053 or 2068 nm, or both at the same time, depending on the outcoupling loss and the pump power. We have achieved laser operation with a maximum slope efficiency of ~92%. This is, to the best of our knowledge, the highest slope efficiency ever demonstrated for any Ho(3+)-doped laser.

Efficient, resonantly pumped, room-temperature Er3+:GdVO4 laser.

We report an efficient room-temperature operation of a resonantly pumped Er3+:GdVO4 laser at 1598.5 nm. The maximum continuous wave (CW) output power of 3.5 W with slope efficiency of 56% was achieved with resonant pumping by an Er-fiber laser at 1538.6 nm. With pumping by a commercial laser diode bar stack, a quasi-CW (QCW) output of 7.7 W and maximum slope efficiency of ~53% versus absorbed pump power were obtained. This is believed to be the first resonantly (in-band) pumped, room-temperature Er3+:GdVO4 laser.

Spectroscopic properties and laser performance of resonantly-pumped cryo-cooled Er³âº:GdVO4.

We report a highly efficient cryo-cooled eye-safe laser operation of a resonantly-pumped (in-band) Er³âº:GdVO4 single crystal. The maximum continuous wave (CW) power of 10.3 W with 84% slope efficiency was achieved at 1598.7 with pumping at 1538.6 nm by a spectrally-narrowed Er-fiber laser. Under the 1529 nm resonant pumping by a commercially available diode bar stack operating in a quasi-CW (QCW) mode, the laser delivered 37 W of output power with 68% slope efficiency. This is believed to be the first reported cryo-cooled Er³âº:GdVO4 laser, resonantly-pumped into the 4I15/2 →4I13/2 transition.

High power diode-pumped 2.7-µm Er3+:Y2O3 laser with nearly quantum defect-limited efficiency.

We report diode-pumped Er3+:Y2O3 ceramic laser with ~14 W of true CW output at ~2.7 µm. This presents nearly ten-fold power increase with respect to previous best result with this laser material. We also believe this to be the highest power ever reported from Er3+ -doped bulk crystalline laser operating in a ~3-µm wavelength range. Power-scaled performance of 974-nm pumped Er3+:Y2O3 laser was achieved with the slope efficiency of ~26%.

Spectroscopic characterization and laser performance of resonantly diode-pumped Er(3+)-doped disordered NaY(WO4)2.

We report what is believed to be the first resonantly pumped laser operation based on Er(3+)-doped disordered double tungstate single crystal. Efficient laser operation of an Er(3+):NaY(WO(4))(2) laser at ∼1609.6 nm was demonstrated with the naturally wideband, ∼20 nm, InGaAsP/InP laser diode pumping at ∼1501 nm. Laser wavelength tunability of ∼34 nm was also demonstrated based on disorder-broadened emission features of Er(3+):NaY(WO(4))(2) single crystal.

Nearly quantum-defect-limited efficiency, resonantly pumped, Er3+:YVO4 laser at 1593.5 nm.

Nearly quantum-defect-limited laser operation of a resonantly pumped Er(3+):YVO4 at 1593.5 nm is demonstrated. Maximum slope efficiency of ~85% and true CW power of ~13 W at 1593.5 nm were achieved with a beam propagation factor of M2 ~ 1.05. This slope efficiency is, to the best of our knowledge, the highest efficiency ever reported for a crystalline Er-doped laser.

Composite Yb:YAG/SiC-prism thin disk laser.

We report the first demonstration of a Yb:YAG thin disk laser wherein the gain medium is intracavity face-cooled through bonding to an optical quality SiC prism. Due to the particular design of the composite bonded Yb:YAG/SiC-prism gain element, the laser beam impinges on all refractive index interfaces inside the laser cavity at Brewster's angles. The laser beam undergoes total internal reflection (TIR) at the bottom of the Yb(10%):YAG thin disk layer in a V-bounce cavity configuration. Through the use of TIR and Brewster's angles, no optical coatings, either anti-reflective (AR) or highly reflective (HR), are required inside the laser cavity. In this first demonstration, the 936.5-nm diode pumped laser performed with approximately 38% slope efficiency at 12 W of quasi-CW (Q-CW) output power at 1030 nm with a beam quality measured at M(2) = 1.5. This demonstration opens up a viable path toward novel thin disk laser designs with efficient double-sided room-temperature heatsinking via materials with the thermal conductivity of copper on both sides of the disk.

Efficient resonantly pumped tape cast composite ceramic Er:YAG laser at 1645 nm.

Laser operation of a composite ceramic Er:YAG rod is demonstrated at 1645 nm with a slope efficiency of 56.9% under resonant pumping at 1532.3 nm. This is believed to be the first reported composite ceramic Er:YAG laser and also the first reported use of a tape cast technique for producing laser ceramics.

Resonantly pumped Pr3+-doped eye-safe laser at approximately 1.65 microm.

The first (to our knowledge) resonantly pumped laser action based on the 3F3-->3H4 transition of a Pr3+ ion is demonstrated. Pr3+-doped RbPb2Cl5 laser in-line pumped at approximately 1547 nm exhibited slope efficiency of over 21% at 1676.5 nm, despite the marginal quality of the laser sample available for this proof-of-concept experiment. This is believed to be the first non-Er3+ resonantly pumped approximately 1.6 microm eye-safe laser ever reported.

Highly scalable, resonantly cladding-pumped, Er-doped fiber laser with record efficiency.

We report the performance of a resonantly cladding-pumped, Yb-free, Er-doped fiber laser. We believe this is the first reported resonantly cladding-pumped fiber-Bragg-grating-based, Er-doped, large-mode-area (LMA) fiber laser. The laser, pumped by fiber-coupled InGaAsP/InP laser diode modules at 1,532.5 nm, delivers approximately 48 W of cw output at 1,590 nm. It is believed to be the highest power ever reported from a Yb-free Er-doped LMA fiber. This fully integrated laser also has the optical-to-optical efficiency of approximately 57%, to the best of our knowledge, the highest efficiency reported for cladding-pumped unidirectionally emitting Er-doped laser.

All-Solid-State Tunable Ultraviolet Subnanosecond Laser with Direct Pumping by the Fifth Harmonic of a Nd:YAG laser.

We report what we believe is the first all-solid-state tunable ultraviolet laser pumped by the fifth harmonic of a Q-switched Nd:YAG laser. Our laser based on a Ce(3+):LiLuF(4) active medium stably generates a single, satellite-free, 0.88-ns pulse under 5-ns, 10-Hz repetition rate pumping conditions. A novel tilted-incident-angle side-pumping scheme resulted in a simple laser-cavity design.

Ultraviolet short pulses from an all-solid-state Ce:LiCAF master-oscillator power-amplifier system.

We have developed an all-solid-state master-oscillator-power-amplifier system employing Ce:LiCAF, a new degradation-free tunable ultraviolet laser medium pumped by the fourth harmonic of conventional 10-ns Q -switched Nd:YAG lasers. The low- Q , short-cavity Ce:LiCAF master oscillator produced a satellite-free 1-ns pulse under appropriate pumping-fluence control. 18% energy extraction with sufficient gain was achieved in a single-stage, confocal, double-pass amplifier. As a result, 289-nm, 1-ns, 14-mJ pulses were efficiently obtained from this simple laser system.

Ce(3+):LuLiF(4) as a broadband ultraviolet amplification medium.

Ce(3+):LuLiF(4) is shown to have a broad gain spectrum, which is attractive for short-pulse applications. A large small-signal gain over 6 dB/cm and a sufficiently large saturation fluence of 50 mJ/cm(2) were observed for 10-ns probe pulses under KrF excimer laser pumping. In a confocal four-pass configuration, 17-dB amplification was demonstrated for 325-nm picosecond pulses, and 20-dB gain was demonstrated for cw laser light.

Direct and passive subnanosecond pulse-train generation from a self-injection-seeded ultraviolet solid-state laser.

We propose a passive self-injection-seeding scheme for the generation of short-pulse trains from various pulsed lasers. In this scheme a single subnanosecond pulse is generated from a short-cavity seeding laser. The pulse is then returned to the same gain medium and amplified regeneratively until the gain is quenched completely. Cw operation capability or an external short-pulse seeding laser is not required for generation of short-pulse trains. Based on this simple scheme an ultraviolet subnanosecond pulse train is directly and passively generated from a solid-state laser medium (Ce(3+):LuLiF(4)) pumped by a standard 10-ns laser.

VUV and UV fluorescence and absorption studies of Pr(3+)-doped LiLuF(4) single crystals.

The laser-induced fluorescence spectrum of LiLuF(4):Pr(3+) single crystals, pumped by an F(2) pulsed-discharge molecular laser at 157 nm, was obtained in the VUV and UV regions of the spectrum at room temperature. A number of new fluorescence peaks were observed for the first time to our knowledge. They were assigned to the dipole-allowed transitions 4f5d ? 4f(2) of Pr(3+) ion. In addition, the absorption spectrum of the crystal samples was recorded. The positions of the bands with the 4f5d configuration were found to be 46 412, 53 267, and 63 397 cm(-1) from the ground state, (3)H(4), of the Pr(3+) ion. The edge (onset) of the 4f5d bands was at 45 100 cm(-1).

Spectroscopy and stimulated emission of Nd(3+) in an acentric CsY(2)F(7) host.

The results of preliminary spectroscopic studies of new fluoride single-crystal CsY(2)F(7) that is activated by Nd(3+) ions are given. Direct evidence for the possibility of application of this ordered material as a laser host is given for the first time to our knowledge. Stimulated emission of Nd(3+) ions on the main intermultiplet transition is obtained under both nonselective flash-lamp pumping conditions and continuous Ar ion laser pumping conditions.