Adaptive correction of linear phase aberrations in laser amplifier systems

摘要

Linear phase aberrations in laser amplifier systems are adaptively corrected by a device which propagates an object beam formed by reflection of a laser beam from a target backwards through a laser amplifier chain in order to sample the linear phase aberrations and produces a conjugate image beam by degenerate four-wave mixing in a medium having a third order nonlinearity in susceptibility. The conjugate image beam which is amplified as it propagates back through the laser amplifier chain has the linear phase aberrations removed. The device also corrects for birefringent aberrations contained in the laser amplifier chain when (1) the medium has an isotropic nonlinearity; (2) the polarization of the pump beams, required for four-wave mixing, lies in the plane formed by the object beam and the pump beams; and (3) the angle between the object beams and the pump beams is substantially 90 degrees. The degenerate four-wave mixing is accomplished in one embodiment by gain saturation in Nd:YAG.