Nd:YAG loop resonator with a Cr/sup 4+/:YAG self-pumped phase-conjugate mirror

We demonstrate a Nd:YAG loop resonator with a self-pumped phase conjugate, mirror in a Cr/sup 4+/:YAG crystal, in the nanosecond regime. A maximum extraction of 29 mJ and a maximum reflectivity of 3.3 are obtained. The output beam is a high-quality diffraction-limited TEM/sub 00/ mode and has a pulse shape of /spl sim/20-ns duration, showing the self Q-switching ability of the resonator. In addition, we demonstrate an original and specific configuration of the anisotropic Cr/sup 4+/:YAG crystal that compensates not only for phase aberrations but also for polarization aberrations induced into the loop resonator.