Laser-based ultrasound with linear detection in photorefractive multiple quantum wells

Summary form only given. Laser-based ultrasound is a promising NDE technique for remote sensing, manufacturing diagnostics, and in-service inspection. Nonadaptive homodyne and heterodyne reference beam interferometers could not operate effectively with speckle, and time-delay interferometers (such as the confocal Fabry-Perot) require path-length stabilization to a fraction of an optical wavelength. We use dynamic holography in a photorefractive quantum well, which acts as an adaptive beam splitter to compensate for wave-front distortions. These devices operate close to the quantum noise limit in the presence of speckle and do not require path-length stabilization. Most important, the photorefractive quantum wells have a unique ability to achieve linear homodyne detection regardless of the value of the photorefractive phase shift.