OSCILLATORY MODE-COUPLING AND ELECTRICALLY STROBED GRATINGS IN PHOTOREFRACTIVE QUANTUM-WELL DIODES

Oscillatory mode coupling between two coherent laser beams is produced when an interference pattern moves against a quasi-static electricall y strobed grating in a photorefractive AlGaAs/GaAs multiple-quantum-we ll diode operated in the quantum-confined Stark geometry. The oscillat ion frequency is equal to the frequency difference between the two las er beams and provides a method to measure high-frequency Doppler shift s or large surface displacements for laser-based ultrasound. Combined photorefractive gains (normally forbidden by symmetry in the Stark geo metry) and absorptive gains approach 1200 cm(-1) during two-wave mixin g using moving gratings. (C) 1998 Optical Society of America.