Self-starting Nd : YAG holographic laser oscillator with a thermal grating

Self-starting operation of a self-conjugating loop oscillator is achieved, for the first time to our knowledge, by use of an optically induced thermal hologram in a nonsaturable absorbing medium. Self-Q-switched single-longit udinal-mode pulses of 12-ns duration are obtained in a near-diffraction-lim ited spatial mode and with an output energy of >250 mJ. Good correction of intracavity phase distortions is obtained, as well as good extraction effic iency in the laser mode volume. It is shown that one has to set an addition al nonreciprocal phase-shift element in the loop to ensure resonant operati on of the system. (C) 1999 Optical Society of America.