Passively Q Switched Laser

Scientific Applications and Research Associations (SARA) proposes an R&D program to develop a passively Q-switched Tm:YLF laser using Cr:Zn:Se, Cr:Zn:S, Co:Zn:S, or Co:Zn:S as the solid state saturable absorber. Passive Q-switching reduces cost, weight, volume, eliminates bulky electro-optical active Q-switches and associated electronics, and simplifies resonator design. Passively Q-switched lasers are compact, ruggedized, reliable, packaged to withstand the shock, vibration, pressure, temperature changes, and have nearly diffraction limited beams. The gain crystal, Q-switch, and resonator mirrors can be integrated onto a monolithic device. High average power (>11 W) passively Q-switched Nd:YVO4 lasers using Cr+4:YAG saturable absorber have been demonstrated but pulse energy and repetition rate were ~ 60 J at 190 kHz because of the fast 4 s lifetime of the saturated transition in Cr+4:YAG. However, both Co:Zn:S, and Co:Zn:Se have saturated transition lifetimes ~ 200 to 300 s at 295 K and lifetimes increase to ~ 600 to 800 s at 250 K. This may permit temperature tuning of repetition rate and open up the possibility to CW pumped, high energy (mJ range), high average power passive Q-switching at sub-kHz repetition rates. Benefits of funding include publishing research and commercial applications such as laser scalpels, LIDAR, and pollution monitoring.