Non-steady-state photoelectromotive force effect in photorefractive Sn_2P_2S_6 crystals

Abstract

Results of experimental investigation of the non-steady-state photoelectromotive-force effect in ferroelectric photorefractive Sn2P2S6 crystals at a wavelength of 633 nm are reported. The dominating photoconductivity proved to be of the p type, with a diffusion length of photocarriers of ∼1 µm. This characteristic length proved to be shorter than the Debye-screening length evaluated as ∼3 µm in this crystal. The millisecond characteristic time of the space-charge grating formation was determined by the photoconductivity-relaxation time, which was found to be a little bit longer than the dielectric-relaxation time. Both of them dropped sublinearly with increasing average light intensity in the investigated region I0≃0.5–0.01 mW/mm2.