Adaptive interferometers using photorefractive crystals

The authors report the detailed study of salient features of an adaptive interferometer operating via dynamic two-wave mixing in a cubic photorefractive Bi₁₂SiO₂₀ crystal. Specifically, they measured its transfer function and demonstrated its differentiating and adaptive properties. The latter means that the device can efficiently detect a weak high-frequency phase-modulated signal at the background of a slowly varying jamming signal of a large amplitude. The authors point out that similar adaptive features are also exhibited by the effect of non-steady-state photo-EMF. This effect consists in an alternating photocurrent arising as a result of illumination of a short-circuited simply photoconducting crystal by a vibrating interference pattern