Investigation On Photorefractive Phase Conjugation And Its Applications

The phase-conjugation wave is the wave time-reversed on the amplitude, phase and polarization with another wave. It has many potential applications, including self-adaptive optics, optical computing and optical communications, image processing and real-time holography. In this thesis, we investigate the properties of the phase-conjugate wave produced by the self-pumped in Cu:KNSBN crystal and by the four-wave mixing in Cr:SBN crystal.Based on the band transport model, the formation of refractive index grating in photorefractive crystal is discussed firstly. Then the characteristics of two-wave coupling, four-wave mixing and light-induced scattering are analyzed.The relationship between the incident angle and the self-pumped phase-conjugate(SPPC) reflectivity in Cu:KNSBN is studied. The relation between the photo-voltage, photocurrent of photocell and light intensity measured by photocell is discussed. It can be explained by light-induced scattering that the SPPC wave is diffracted in the course of being produced. We utilize Cu:KNSBN crystal to correct a distorted picture because of its super SPPC characteristic.The experiment show that Cr:SBN crystal has super characteristic of four-wave mixing to produce the phase-conjugate wave. We study the dependence of the phase-conjugate reflectivity of 1000ppm Cr:SBN crystal on the parameters of incidence light such as light intensity ratio and the angle of incidence. We also study the phase-conjugate characteristic of 500ppm Cr:SBN crystal. We draw the conclusion that 1000ppm Cr:SBN crystal has greater phase-conjugate reflectivity than 500ppm Cr:SBN crystal. We find that the phase-conjugate reflectivity depends on the direction of two-wave coupling. We utilize 1000ppm Cr:SBN crystal to correct a distorted picture because of its super phase-conjugate characteristic.