Passive Q switching of a solar-pumped Nd : YAG laser

Passive Q switching is a preferable choice for switching the Q factor of a solar-pumped laser because it requires neither a driver nor an electrical p ower supply. The superior thermal characteristics and durability of Cr4+:YA G single crystals as passive Q switches for lamp and diode-pumped high-powe r lasers has been demonstrated. Here we report on an average power of 37 W and a switching efficiency of 80% obtained by use of a solar-pumped Nd:YAG laser Q switched by a Cr4+:YAG saturable absorber. Concentration of the pum ping solar energy on the laser crystal was obtained with a three-stage conc entrator, composed of 12 heliostats, a three-dimensional compound parabolic concentrator (CPC) and a two-dimensional CPC. The water-cooled passive Q s witch also served as the laser rear mirror. Repetition rates of as much as 50 kHz, at pulse durations between 190 and 310 ns (FWHM) were achieved. Fro m the experimental results, the saturated single-pass power absorption of t he Cr4+ YAG device was estimated as 3 +/- 1%. (C) 2000 Optical Society of A merica.