Non-steady-state photoelectromotive force and two-wave mixing in photorefractive crystals under frequency modulated illumination

Abstract : We report the excitation of non-steady-state photoelectromotive force and two-wave mixing signals using uniformly accelerated motion of the recording light pattern. Such illumination is created by linear frequency modulation of the interfering light beams. The pulse response is predicted theoretically and observed experimen- tally in GaAs and Bi12TiO20 crystals at λ 633 nm. The evolution of the pulse shape versus sweep rate is demonstrated and explained in the frames of the developed theory. The application of the effects in laser Doppler velocimeters and accelerometers is discussed as well.