Image restoration based on phase conjugation in second order nonlinear composite under reflection configuration

Previously, we demonstrated that recovery of image blurred by phase aberration and atmospheric turbulence through optical phase conjugate beams generated by difference-frequency generation. In Refs. [1,2], the images were restored by the phase-conjugation in the transmission configuration. Based on such a scheme, the image system overcomes the disadvantages which were suffered in the past, such as slow response rate based on photorefractive effect, requiring large pump powers based on four-wave mixing. In contrast, based on the scheme demonstrated in Refs. [1,2], the response time is limited by the pulse width or modulation speed, and therefore, it is perhaps the only scheme which can restore the blurred images caused by dynamic atmospheric turbulence. In addition, the pump power required to achieve the conversion efficiency of 100% from the input beam to the phase-conjugate beam can be in principle reduced to several miliwatt. In an AFB-KTP nonlinear composite, one pair of the signal and idler was split into two sets of the highly-coherent signals and idlers. The perpendicular polarizations of the signals and idlers make this new scheme insensitive to the polarization of the input beam in restoration of distorted images.