Influence of V:YAG saturable absorber orientation on linearly polarized laser Q-switching

Abstract

The impact of the V:YAG saturable absorber nonlinear transmission polarization anisotropy on Q-switched laser system was investigated. Two various cuts ([111] and [100]) of V:YAG crystal with the same initial transmission 87% @ 1.3 μm were used as a passive Q-switch for longitudinaly diode pumped linearly polarized Nd:YAP laser operating at 1342 nm. This laser consisted of 8.2mm long Nd:YAP crystal placed in 100mm long semihemisferical resonator. The flat mirror in vicinity of Nd:YAP crystal was transparent for pumping radiation at 805nm and highly reflecting at operating wavelength 1342 nm. The curved output coupler (radius of curvature 146mm) had reflectivity 92% @ 1342 nm. The laser was tested under pulsed pumping for the duty-cycle 9% and under CW pumping. The laser output parameters (mean output power, pulse width, repetition rate, energy, and peak power) were measured for absorber turning around longitudinal crystal axis. In this configuration for [111]-cut of V:YAG the pulse energy and pulse width (FWHM) varied from 27 up to 38 μJ and from 50 to 40 ns, respectively. This corresponds to peak power rise from 0.55 up to 0.95kW. In case of [100]-cut the proper orientation of V:YAG in respect to oscillating radiation polarization allowed to increase pulse energy from 37 to 60 μJ and peak power from 1.3 to 3 kW. Simultaneously, the pulse width decreased from 28 to 20 ns. The results showed that proper choice of saturable absorber cut and orientation can significantly improve giant pulse parameters.