An 8.2 J phase-conjugate solid-state laser coherently combining eight parallel amplifiers

We describe a phase-conjugate master oscillator-power amplifier configuration in which as many as eight parallel flashlamp-pumped Cr:Nd:GSGG amplifiers and four parallel CD*A frequency doubling crystals were coherently combined. Operating at a pulse repetition frequency of 1.25 Hz, we demonstrated an output energy of 8.2 J at 1 μm and 4.4 J at 530 nm for a 54% frequency-doubling efficiency. This effort represents the highest reported output energy achieved using coherent coupling via phase conjugation. In subsequent experiments at a pulse repetition frequency of 5 Hz, we produced ~22 W of 1.06 μm average power with a beam quality that was ~2.5 times diffraction-limited. The observed far-field intensity profile indicates that we achieved effective and consistent compensation of optical-path length differences among the multiple parallel amplifiers and frequency-doubling crystals