Er/Yb glass Q-switched lasers with optimized performance

We characterize several configurations of compact, Q-switched, 1.5 um lasers based on Er/Yb doped glass. Such lasers are required for eye-safe laser range-finders (LRF), laser markers, and illuminators for 3D and gated imaging. While 1-3 Hz pulse repetition frequency (PRF) is adequate for LRFs, the other applications require much higher PRFs to achieve near-real-time image refresh rates. Lasers described here utilize Er/Yb glass active elements, side-pumped by a 940 nm laser diode bar, or end-pumped by a fiber-coupled laser diode, and made use of active or passive Q-switching (PQS) techniques. Active Qswitching is implemented with resonant scanning mirror, and PQS utilizes Co:Spinel saturable absorbers. Q-switched pulse energies of 5mJ and 3mJ are achieved with side-pumping and end-pumping, respectively. An optical efficiency of over 3.7%, the highest to our knowledge for a PQS Er/Yb glass laser, is measured for the end-pumped implementation. When configured to generate 1mJ, the endpumped PQS laser operates over a 2-25 Hz PRF range, with nearly constant pulse energy and optical efficiency. Features and advantages of the various laser configurations are compared.