GIANT ENHANCEMENT OF LOW-FREQUENCY NON-STEADY-STATE PHOTO-EMF SIGNAL IN BI12SIO20 CRYSTAL UNDER EXTERNAL DC BIAS

We present experimental results which demonstrate that non-steady-stat e photo-EMF, induced by vibrating interference fringes in Bi12SiO20 ph otorefractive crystal can be dramatically (by a factor of 10(3) in our experimental conditions) enhanced in a resonance regime under applica tion of an external DC field. We show that for increasing applied elec tric field the resonance maximum moves from the dielectric relaxation frequency towards the low frequency end. Its magnitude grows as E-0(2) for low values of the field, for high external field significant broa dening of the resonance peak and linear growth of the signal resonance amplitude is observed. This effect and non-trivial dependence of the resonance signal amplitude on the spatial frequency of the pattern is explained by saturation of the space charge grating. Finally, the sens itivity of the biased resonance adaptive photo-EMF detector is estimat ed. (C) 1998 Elsevier Science B.V. All rights reserved.