Two-wave mixing with time-modulated signal in Bi12SiO20 theory and application to homodyne wave-front detection

Abstract

We theoretically analyze a two-wave mixing interaction in photorefractive Bi12SiO20 crystals in which the amplitude of the signal beam is time modulated at high frequency. Calculations of the photoinduced space-charge field are derived for a sinusoidal modulation of the input signal. Due to the time-integrating properties of the nonlinear crystal, the transmitted signal exhibits a differential gain when the modulating frequency is much greater than the inverse of the material response time. Application to coherent homodyne detection of wave fronts carrying spatial and temporal information is also presented.