PACS 42.65.Sf – Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics PACS 42.70.Nq – Other nonlinear optical materials; photorefractive and semiconductor materials Abstract – We report the excitation of the non-steady-state photoelectromotive force using a uniformly accelerated motion of the recording light pattern. Such illumination is created by the linear frequency modulation of the interfering light beams. The pulsed response is observed experimentally in a semi-insulating GaAs crystal at a light wavelength of 633 nm. The evolution of the pulse shape vs. sweep rate is demonstrated. We also discuss the possible application of the effect in laser Doppler velocimeters and accelerometers.