Lisen Zhang

High power and good beam quality of two-dimensional VCSEL array with integrated GaAs microlens array.

High power and good beam quality of two-dimensional bottom-emitting vertical-cavity surface-emitting laser array with GaAs microlens on the substrate is achieved. Uniform and matched convex microlens is directly fabricated by one-step diffusion-limited wet-etching techniques on the emitting windows. The maximum output power is above 1 W at continuous-wave operation at room temperature, and the far-field beam divergence is below 6.6° at a current of 4 A. These properties between microlens-integrated and conventional device at different operating current are demonstrated.

Design and comparison of GaAs, GaAsP and InGaAlAs quantum-well active regions for 808-nm VCSELs

Vertical-cavity surface-emitting lasers emitting at 808 nm with unstrained GaAs/Al0.3Ga0.7As, tensilely strained GaAs(x)P(1-x)/Al0.3Ga0.7As and compressively strained In(1-x-y)Ga(x)Al(y)As/Al0.3Ga0.7As quantum-well active regions have been investigated. A comprehensive model is presented to determine the composition and width of these quantum wells. The numerical simulation shows that the gain peak wavelength is near 800 nm at room temperature for GaAs well with width of 4 nm, GaAs0.87P0.13 well with width of 13 nm and In0.14Ga0.74Al0.12As well with width of 6 nm. Furthermore, the output characteristics of the three designed quantum-well VCSELs are studied and compared. The results indicate that In0.14Ga0.74Al0.12As is the most appropriate candidate for the quantum well of 808-nm VCSELs.

High power 4.65 μm single-wavelength laser by second-harmonic generation of pulsed TEA CO2 laser in AgGaSe2 and ZnGeP2

A high power 4.65 μm single-wavelength laser by second-harmonic generation (SHG) of TEA CO2 laser pulses in silver gallium selenide (AgGaSe2) and zinc germanium phosphide (ZnGeP2) crystals is reported. Experimental results show that the average output power of SHG laser is not only restricted by the damage threshold of the nonlinear crystals, but also limited by the irradiated power of fundamental-wave laser depending on the operating repetition-rate. It is found that ZnGeP2 can withstand higher 9.3 μm laser irradiation intensity than AgGaSe2. As a result, using a parallel array stacked by seven ZnGeP2 crystals, an average power of 20.3 W 4.65 μm laser is obtained at 250 Hz. To the best of our knowledge, it is the highest output power for SHG of CO2 laser by far.

High-Power-Density High-Efficiency Bottom-Emitting Vertical-Cavity Surface-Emitting Laser Array

We report on the lasing characteristics of a two-dimensional (2D) vertical-cavity surface-emitting laser (VCSEL) array with three In0.2GaAs/GaAs0.92P QWs emitting at 977 nm. The contribution of a large-bandgap barrier material, GaAsP, to improve the output power was investigated. More than 123 W of pulsed peak power at 110 A was achieved, corresponding to 24.6 kW/cm2 of power density and 1.11 W/A of slope efficiency. The thermal effect dependence of the characteristics of the array was illustrated. Moreover, the device performance was estimated by a functional method using a p-parameter.

Computer modeling and experimental study of non-chain pulsed electric-discharge DF laser

Computer simulation and experimental study of a pulsed electrical-discharge DF laser pumped by the SF(6)-D(2) non-chain reaction are presented. The computer model encompassing 28 reactions is based on laser rate equations theory, and applied to approximately describe the chemical processes of non-chain DF laser. A comprehensive study of the dependence of number density on time for all particles in the gain area is conducted by numerical calculation adopting Runge-Kutta method. The output performance of non-chain pulsed DF laser as a function of the output mirror reflectivity and the mixture ratio are analyzed. The calculation results are compared with experimental data, showing good agreement with each other. Both the theoretical analysis and experimental results present that the laser output performance can be improved by optimizing the mixture ratio and output mirror reflectivity. The optimum values of mixture ratio and output mirror reflectivity are respectively 10:1 and 30%. The single pulse energy of 4.95J, pulse duration of 148.8ns and peak power of 33.27 MW are achieved under the optimum conditions.

Stimulated rotational Raman scattering at multiwavelength under tea CO2 laser pumping with a multiple-pass cell

Stimulated rotational Raman scattering (SRRS) at multiwavelength pumped by TEA CO2 laser was demonstrated in this paper. Raman mediums were cooled by liquid-N2 and a multiple-pass cell (MPC) with 25 passes was designed and used. When the para-H2 was pumped by single-longitudinal-mode (SLM) circular polarized TEA CO2 laser on 10P(20), 9P(20), and 10R(20), 50 mJ 16.95 μm, 350 mJ 14.44 μm, and 536 mJ 16.9 μm radiations were obtained, corresponding to energy conversion efficiency of 1.2, 11.7, and 13.4%, respectively. When the ortho-D2 was pumped by CO2 laser on 10R(18), 108 mJ 12.57 μm Raman laser was obtained with energy conversion efficiency of 2.9%.

Diode-pumped high-repetition-rate acousto-optically Q-switched Nd:YVO4 laser operating at 914 nm

A diode-pumped high-repetition-rate acousto-optically (A-O) Q-switched Nd:YVO4 laser operating at 914 nm was reported in this paper. Employing a compact linear laser cavity, at an operating repetition rate of 10 kHz, a maximum average output power of 2.2 W 914 nm laser was obtained at an incident pump power of 45.3 W, corresponding to an optical conversion efficiency of 4.9% and a slope efficiency of 8.8%. Minimum pulse width of 24 ns and maximum peak power of 8.0 kW of 914 nm laser was also achieved at an incident pump power of 40.8 W. To the best of our knowledge, this is the highest peak power of 914 nm laser at 10 kHz by far. Moreover, the highest operating repetition rate of pulsed 914 nm can even reach 100 kHz.

Diode-pumped acousto-optically Q-switched high-repetition-rate Nd:YAG lasers at 946 and 473 nm by intracavity frequency-doubling

A diode-pumped acousto-optically (AO) Q-switched high-repetition-rate Nd:YAG lasers at 946 and 473 nm by intracavity frequency-doubling were reported in this paper. Using a compact V-type laser cavity, a maximum average output power of 4.5 W 946 nm laser was obtained at an operating repetition rate of 10 kHz, corresponding to an optical conversion efficiency of 10.5% and a slope efficiency of 15.6%. With a BiBO crystal as the intracavity frequency-doubler, 1.35 W 473 nm pulsed laser was achieved at 10 kHz. The peak power of the Q-switched blue pulse was up to 4.1 kW, with a pulse width of 33.1 ns. Then, the long-term power instability was less than 1%. Moreover, stable pulsed operation of 946 nm and 473 nm lasers can even reach 50 kHz.