Passive Q-switching of a self-pumped phase-conjugate Nd : YAG loop resonator

Q-switched regimes of a nanosecond pulse-periodic Nd :YAG laser with a self -pumped phase-conjugate loop cavity are investigated. A Sagnac interferomet er as the laser cavity rare mirror is applied for angular selection of init ial laser radiation. Two Flashlamp-pumped Nd : YAG rods placed at the inter section of laser beams produce both gain and laser output coupling. As a pa ssive Q-switch, a LiF : F-2(-) crystal is used, which also increases diffra ction efficiency of intracavity phase conjugation. Two schemes with differe nt LiF : F-2(-) crystal positions inside the cavity are considered. In the optimum position, a low-divergence (3.4 x 10(-4) rad), diffraction-limited (M-2 = 1.15) laser output radiation achieves 4 MW peak power and 50 W avera ge power, which is 12% higher than that in the free-running mode.