LASER-BASED ULTRASOUND DETECTION USING PHOTOREFRACTIVE QUANTUM-WELLS

We demonstrate a laser-based adaptive ultrasonic homodyne receiver usi ng dynamic holography in AlGaAs/GaAs photorefractive multiple quantum wells. The dynamic hologram acts as an adaptive beamsplitter that comp ensates wavefront distortions in the presence of speckle and requires no path-length stabilization. The photorefractive quantum wells have t he unique ability to achieve maximum linear homodyne detection regardl ess of the value of the photorefractive phase shift by tuning the exci tonic spectral phase. We achieve a root mean square noise-equivalent s urface displacement of 6.7 x 10(-7) Angstrom (W/Hz)(1/2). (C) 1998 Ame rican Institute of Physics. [S0003-6951(98)02434-6].