Accelerating space-charge gratings in wide-bandgap semiconductors as a tool for simultaneous velocity and acceleration measurement

We study the excitation of the two-wave mixing and non-steady-state photoelectromotive force signals using uniformly accelerated motion of the recording light pattern. Such illumination is created by the linear frequency modulation of the interfering light beams. The pulse response is predicted theoretically and observed experimentally in Bi12TiO20 and GaAs crystals lambda=633 nm. We analyse both the diffusion and space-charge wave regimes of signal excitation. The evolution of the pulse shape versus the chirp 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.