PHASE MODULATION SPECTROSCOPY OF SPACE-CHARGE WAVE RESONANCES IN BI12SIO20

A new experimental method for the study of resonance effects and space -charge wave excitation in photorefractive Bi12SiO20 crystals by using a combination of frequency detuning and phase modulation technique ha s been developed. The accuracy of the method allows a detection of res onance peaks of diffraction efficiency within 0.5 Hz. Numerical simula tions of the nonlinear differential equations describing the behaviour of the space-charge waves in photorefractive crystals have been perfo rmed and found to be in a good agreement with experiment. We have meas ured the photocurrent through the crystal and revealed its resonance d ependence, A minimum of electric current through the sample correspond s to the main resonance detected by phase modulation technique.