Dark decay behaviors of photorefractive gratings in self-pumped phase conjugation with Ce:BaTiO3 at 532 and 790 nm wavelengths

Abstract

Dark decay behaviors of photorefractive gratings in self-pumped photorefractive phase conjugation (SPPC) with Ce:BaTiO 3 are studied by measuring the decay of SPPC reflectivities at 532 and 790 nm wavelengths at room temperature. Four-wave mixing by stimulated photorefractive backscattering (SPB-FWM) mechanism and four-wave mixing by total internal reflection (TIR-FWM) mechanism coexist in SPPC at each wavelength. SPB-FWM dominates in SPPC at 532 nm whereas the reverse is true at 790 nm. The stronger the effect of SPB-FWM is, the faster the SPPC grating decays. It is found that two deep traps, i.e., Fe-ion deep trap and Ce-ion deep trap, both make contributions to the SPPC grating. It is also deduced that SPB-FWM forms the charge grating in Fe-ion deep trap, while TIR-FWM builds up the charge grating in the Ce-ion deep trap.