27-W passively mode-locked Nd:YAG laser

Summary form only given. Passively mode-locked lasers with high average power are interesting for numerous applications involving nonlinear frequency conversion, for example RGB laser projection displays. Peak powers in the multi-kW regime allow for efficient frequency conversion in a single pass through a nonlinear crystal. We present a passively made-locked Nd:YAG laser with an average output power of 27 W, a pulse energy of 0.5 /spl mu/J, and a peak power of 20.5 kW directly out of the oscillator. The pulse repetition rate is 55 MHz and the pulse duration 21 ps. The laser contains three laser heads, each side-pumped by two 20-W diode bars. Stable, self-starting passive mode-locking without any Q-switching instabilities is achieved using a semiconductor saturable absorber mirror (SESAM). A single pass through a 10-mm-long LBO crystal for type I non-critical phase matching at 150/spl deg/C results in an average power of 16.2 W of second-harmonic radiation. This corresponds to a conversion efficiency of 60%. The output of the oscillator, which is close to diffraction-limited, is focused to a radius of /spl ap/20 /spl mu/m in the crystal.