Plano-plano Cavity Research Articles

Continuous-wave and passively Q-switched pulse 1060 nm Nd:GdPO4 lasers

1060 nm continuous-wave and passively Q-switched pulse lasers were demonstrated in a 3.5-mm-thick X-cut Nd:GdPO4 crystal. At an absorbed pump power of 1.91 W, a 1060 nm continuous-wave laser with a maximum output power of 0.72 W and a slope efficiency of 42% was realized. When a Cr4+:YAG saturable absorber with an initial transmission of 85% was used, a passively Q-switched pulse laser with repetition frequency of 6.7 kHz, pulse energy of about 19 µJ, pulse duration of 58 ns, and peak power of 0.33 kW was obtained in a plano-concave cavity with a length of 95 mm and an absorbed pump power of 1.91 W. For a plano-plano cavity with a length of 9 mm and the same pump power, a pulse laser with repetition frequency of 7.2 kHz, pulse energy of about 14.1 µJ, pulse duration of 4.1 ns and peak power of 3.4 kW was obtained.

Passively Q-switched Nd:GGG laser at 1110.2 nm by Cr:YAG

A continuous-wave (CW) and passively Q-switched Nd:GGG laser operating at 1110.2 nm is achieved in a rather compact 40 mm plano-plano cavity. By suitably suppressing the lines at 1062, 937, 1105 and 1331 nm by the chosen cavity having a refined coating design, a single-wavelength line at 1110.2 nm is generated. For CW operation, the output power is 1815 mW at the 808 nm pump power of 8.16 W with an optical–optical conversion efficiency of 22.2%. In the pulse mode, the minimum pulse width and the maximum peak power are 20.2 ns and 2.9 kW, respectively.

Continuous-wave and passively Q-switched Nd:YVO4 laser at 1085 nm

An admirable and efficient Nd:YVO4 laser at 1085 nm is demonstrated with a compact 35 mm plano-plano cavity. A chosen narrow bandpass filter with high-transmittance (HT) coating at 1064 nm (T=96%) and optimized part-reflection (PR) coating at 1085 nm (T=15%) is used as the output coupler. In the continuous-wave (CW) regime, the maximum output power reaches 3110 mW at the pump power of 11.41 W. Based on a Cr:YAG crystal with initial-transmittance of 91%, the first passively Q-switched Nd:YVO4 laser at 1085 nm is achieved. When the pump power is changed from the threshold of 4.50 to 6.08 W, the dual-wavelength lines at 1064 and 1085 nm are generated simultaneously. However, at the pump power of above 6.08 W, the single-wavelength line at 1085 nm is achieved. The largest output power, the highest peak power, and the narrowest pulse width are 1615 mW, 878 W and 26.2 ns, respectively.

Focusing metasurface quantum-cascade laser with a near diffraction-limited beam.

A terahertz vertical-external-cavity surface-emitting-laser (VECSEL) is demonstrated using an active focusing reflectarray metasurface based on quantum-cascade gain material. The focusing effect enables a hemispherical cavity with flat optics, which exhibits higher geometric stability than a plano-plano cavity and a directive and circular near-diffraction limited Gaussian beam with M2 beam parameter as low as 1.3 and brightness of 1.86 × 106 Wsr-1m-2. This work initiates the potential of leveraging inhomogeneous metasurface and reflectarray designs to achieve high-power and high-brightness terahertz quantum-cascade VECSELs.

Passive Q-switching of Yb bulk lasers by a graphene saturable absorber

Compact Yb:KLu(WO4)2 and Yb:LuVO4 lasers diode-pumped at 978 nm are passively Q-switched by a single-layer graphene saturable absorber. The Yb:KLu(WO4)2 laser generated 165 ns/0.49 μJ pulses at 1030 nm with 170 mW average output power and 12 % slope efficiency. With the Yb:LuVO4 laser, 152 ns/0.83 μJ pulses were achieved. The output power reached 300 mW at 1024 nm, and the slope efficiency was 10 %. Laser operation in a plano-plano cavity is achieved with both crystals with thermal lensing playing a key role in their performance. A model describing graphene Q-switched Yb lasers is developed. Our results indicate the potential of graphene for passive Q-switching of ~1 μm bulk lasers.

Passively Q-switched 15-16 μm Er:Yb:LuAl_3(BO_3)_4 laser with Co^2+:Mg_04Al_24O_4 saturable absorber

Using a Co(2+):Mg(0.4)Al(2.4)O(4) spinel crystal as saturable absorber, efficient passively Q-switched pulse laser operating at 1.5-1.6 μm was realized in an Er:Yb:LuAl(3)(BO(3))(4) crystal end-pumped by a 970 nm diode laser. At absorbed pump power of 15.7 W, 1540 nm laser with 28.6 μJ energy, 40 ns duration and 22 kHz repetition rate, and 1520 nm laser with 9.9 μJ energy, 37 ns duration and 63 kHz repetition rate were obtained in a plano-concave cavity, respectively. For a plano-plano cavity, corresponding values of 1520 nm laser were 16.3 μJ, 14 ns and 41 kHz, respectively, and the maximum output peak power was about 1.16 kW.

Generation of radially polarized beams based on thermal analysis of a working cavity

The laser oscillation and polarization behavior of a side-pumped Nd:YAG laser are studied theoretically and experimentally by a thermal model for a working cavity. We use this model along with the Magni method, which gives a new stability diagram, to show important characteristics of the resonator. High-power radially and azimuthally polarized laser beams are obtained with a Nd:YAG module in a plano-plano cavity. Special regions and thermal hysteresis loops are observed in the experiments, which are concordant with the theoretical predictions.

Improved performance of diode-end-pumped Nd:GdVO4 912 nm laser property with indium solder technology

A novel indium-solder technology is demonstrated to deal with the serious thermal dissipation problem in the 912 nm Nd:GdVO4 laser operation. By use of indium-solder between the laser rod and the heat-sink, the contact resistance is reduced by removing the air bubble and heat conducting silicon and the boundary heat transfer coefficient is raised. After the indium-solder was used, it is found that the temperature in the laser rod and the deformation in the pumping end surface are eased remarkably based on a simulation of finite element analysis. Experimental results show that the continuous-wave 912 nm laser performance is improved obviously, both in a plano-plano cavity and a plano-concave cavity.

Efficient quasi-continuous-wave and passively Q-switched laser operation of a Nd^3+:BaGd_2(MoO_4)_4 cleavage plate

Pumped by a Ti:sapphire laser at 807 nm, efficient quasi-cw and passively Q-switched laser operations have been realized from a 1.1 mm thick, 1.2 at. % Nd(3+):BaGd(2)(MoO(4))(4) cleavage plate in a plano-plano cavity. When the absorbed pump power was 1060 mW, the achieved maximum quasi-cw output power was 580 mW. The slope efficiency and absorbed pump threshold power were 60% and 50 mW, respectively. Using a Cr(4+):YAG crystal with an initial transmission of 85% as the saturable absorber, a pulse laser with 3.0 microJ energy, 30 ns duration, and 52 kHz repetition rate has been obtained when the absorbed pump power was 1060 mW. The polarization characteristic and laser spectra of both the quasi-cw and passively Q-switched lasers have been measured.

评估Q开关Tm,Ho:GdVO4激光器泵浦的ZnGeP2光学参量振荡器性能

A doubly resonant ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a novel Tm,Ho:GdVO4 laser was demonstrated. Cryogenic Tm(5 at.-%), Ho(0.5 at.-%):GdVO4 laser with high pulse repetition frequency (PRF) of 10 kHz at 2.05 microns was employed as pumping source of ZGP OPO. The 15-mm-long ZGP crystal, 55° cut for I-type phase-matching with low absorption coefficient less than 0.05 cm-1 at 2 ?m, was placed in a plano-plano cavity with resonator length of 30 mm. The ZGP OPO generated a total combined output power of 1.2 W at 3.75 and 4.52 ?m under pumping power of 5.3 W, corresponding to slope efficiency of 40% from incident 2-?m laser power to mid-infrared (Mid-IR) output. A widely tunable range from 3.0 to 6.5 ?m was achieved by changing the crystal angle only 3.5°.

Laser performance of Nd:LaB3O6 cleavage microchips passively Q-switched with a Cr4+:YAG saturable absorber

Passively Q-switched laser oscillation at 1060 nm from an unprocessed Nd:LaB3O6 cleavage microchip with a Cr4+:YAG saturable absorber has been demonstrated. The influence of absorbed pump power, output coupler transmission and cavity length on the output pulse characteristics has been investigated. For a plano-concave cavity with a cavity length of 28 mm, pulse with 100 mW average output power, 4.0 μJ energy, 17 ns duration, 25 kHz repetition rate, and 0.24 kW, peak power was obtained at the absorbed pump power of 1.42 W and output coupler transmission of 3.5%. For a plano-plano cavity with a cavity length of 5 mm, pulse with 85 mW average output power, 2.1 μJ energy, 2.3 ns duration, 40 kHz repetition rate, and 0.89 kW, peak power was obtained at the absorbed pump power of 1.42 W and output coupler transmission of 5.6%. Because a chopper with a 5% duty cycle was employed in the experiments to reduce the influence of pump-induced thermal loading, the above average output powers were obtained at the 5% duty cycle and extrapolated to 100%.

Single-longitudinal-mode operation and second-harmonic generation of Nd:YVO_4 microchip lasers

A single-mode output of 221 and 16 mW for the fundamental and second-harmonic light was obtained with the combination of a Nd:YVO(4) microchip laser and an intracavity KTP crystal. It was found that the beam size and laser power in a plano-plano cavity were dependent on the absorption coefficient of the laser medium and that the material that had a higher absorption coefficient produced higher output power and smaller beam size in the laser cavity. This means that Nd:YVO(4) is suitable not only for single-mode oscillation but also for efficient intracavity second-harmonic generation.