Conditions for neutralizing unwanted photorefraction in a laser with negative electrooptic feedback

The stability regions of high-energy, single-pulse, microsecond- and millisecond-range lasers are analyzed for the case of quasi-cw pumping with negative electrooptic feedback. The approximation of an instantaneous negative feedback is used, and integration in the feedback loop is taken into account. The unwanted photorefraction in DKDP crystals is analyzed. This photorefraction is an additional and very effective factor in the excitation of spiking in these lasers. The photorefraction is treated in the linear approximation and is assumed to occur once a threshold oscillation power is reached in the laser. Those parameter values of the feedback loop which completely neutralize the photorefraction at a high power or energy of the single-pulse lasing are determined. The results derived here can be used to develop computer-controlled, high-energy, single-pulse lasers with programmable output-pulse characteristics.