70-W average-power doubly resonant optical parametric oscillator at 2 μm with single KTP

Abstract

We have demonstrated a high-power intracavity-pumped doubly resonant optical parametric oscillator (OPO) at 2 lm with single-type II phase-matched KTP. A linearly polarized Q-switched solid-state Nd:YAG laser was used as the intra-cavity pump source, of which the output power and beam quality were improved by cascading two laser rods for compensating the thermal birefringence as well as by placing double acoustic-optical Q-switches orthogonally, and the output power of the doubly resonant OPO was studied versus the temperature of KTP and the repetition rate of the Q-switch. The output power was insensitive to the temperature of KTP in a wide range, and 70-W average power was obtained at 2 lm with the repetition rate of 5 kHz. The stability of the OPO laser was measured to be \3.5 % root mean square at the output power of 70 W for 400 s.

Comparative study of intracavity KTP-based Raman generation between Nd:YAP and Nd:YAG lasers operating on the ^4F_3/2 → ^4I_13/2 transition

“…The potassium titanyl phosphate (KTP) crystal is a well-known nonlinear crystal for producing coherent radiations covering a large portion of the spectral range through second harmonic generation [9,10], sum and difference frequency generation [7,11], and optical parametric oscillation [12,13]. Besides the second-order nonlinear response, the early research of the spontaneous Raman spectrum [14] indicated the feasibility of the KTP crystal to be a practical frequency converter via stimulated Raman scattering (SRS), an attractive method of wavelength conversion based on the third-order nonlinearity [15][16][17][18].…”