150 kHz, 300 ps green laser frequency doubled from a linearly polarized passively Q-switched Nd:YAG/Cr4+:YAG microchip oscillator and a Nd:YVO4 amplifier

Abstract

We report the design and performance of a compact solid-state green laser capable of producing a 300 ps pulse width (PW) at a pulse repetition rate (PRR) of 150 kHz. The green laser was comprised of a thermally bonded [111]-cut Nd:YAG and [110]-cut Cr4+:YAG microchip, a Nd:YVO4 crystal, and a hydrothermal grey-track resisted KTP crystal, serving as the oscillator, amplifier and nonlinear frequency converter, respectively. The optimal working conditions for efficient laser amplification and nonlinear frequency conversion were studied by numerical solving the rate equations and coupled wave equations, respectively. Experimental setups were constructed thereafter according to the simulated results. Stable single-longitudinal-mode-operated, linearly polarized (LP) pulses with PW of ∼ 350 ps, PRR of ∼ 150 kHz, and polarization extinction ratio > 13 dB were obtained from the oscillator. The average power was boosted from 285 mW to 1.8 W by the amplifier and then frequency doubled to 532 nm with an average power of 970 mW, resulting in a shorter PW of ∼ 300 ps. The long term power stability of 0.63% (rms) was measured in 200 min indicating its great potential for practical Lidar applications. To the best of our knowledge, these results are among the highest PRR from a LP Nd:YAG/Cr4+:YAG based green laser with PW ≤ 300 ps. The design procedure has also provided an effective way towards the construction of compact solid-state laser systems with oscillation, amplification, and nonlinear frequency conversion units.