High power Nd:YAG laser with self-pumped phase-conjugate loop cavity and repetitive pulsed diode-matrix side-pumping

The joule-range high-beam-quality Nd³⁺:YAG laser oscillation in the multiloop self-pumped phase-conjugate cavity without an output coupling mirror at four-wave mixing of intracavity beams directly in the 110-mm long Nd³⁺:YAG rod with 12.6 kW diode side-pumping is developed and studied. The oscillation efficiency of up to 18 % and average power of up to 22 W were achieved in the optimized geometry of the laser cavity at the 13.9 kW pumping with repetition rate of up to 20 Hz and pulse duration of up to 475 μs. The laser generated a single high-intensive 200-ns giant laser pulse (or series of such pulses with microsecond period at increased pumping) oscillated at self-Q-switch on gain gratings with relatively narrow linewidth of about 2 GHz followed by low-intensive free-running wideband lasing. We also realized a passive Q-switch by the F₂^-:LiF and Cr⁴⁺:YAG crystals with oscillation of pulse trains and also 30-ns single-pulse oscillation with an individual pulse energy of up to 60 mJ and peak power of up to 4 MW at narrowed laser spectra down to 1.7 GHz.