Analysis of and experiment on time response of four‐wave mixing in a photorefractive crystal

Abstract

AbstractTime variations of four‐wave mixing in photore‐fractive crystals is analyzed, and its relation to the physical parameters of the crystal is clarified. Experiments on phase‐conjugate light generation in a BaTiO3 crystal are performed, and the measured data are compared against the results of numerical calculations.Time variations of the coupling coefficient of the photorefractive effect and its relation to the physical parameters of the crystal are derived first and then the phase‐conjugate reflectivity of the transmission‐type diffraction grating is investigated. The pump ratio (the fraction of the forward to the backward pump intensities) and its effects on the time response of the phase‐conjugate reflectivity is for the first time clarified by numerical calculations. Experiments on phase‐conjugate light generation by four‐wave mixing in BaTiO3 are then done and the steady‐state power of the phase‐conjugate light together with the time response to steady state are measured. Finally, the effects of the pump ratio on the phase conjugate power and its time response are compared against experimental data. As a result, it is shown that when the pump ratio is increased nine times, the steady‐state power of the phase‐conjugate light increases approximately 30 times, theoretically, while the measured data indicates an increase that is 24 times. On the other hand, the time response is shown to be delayed four times, theoretically, while the measured value shows a delay of four and a half times. From these results, it is concluded that the time response of the BaTiO3 crystal can be controlled by adjustment of the pump ratio.