*** ABSTRACT 96-60966 Klein This Small Business Innovation Research Phase I project addresses enhanced photorefractive multiple quantum wells for laser ultrasonic receivers. Laser-based ultrasound is a promising nondestructive evaluation technique that can provide remote measurements of parts which are at high temperatures or in hostile environments. It can also be used for parts which are moving rapidly or which require scanning of large areas. Most current receivers for laser-based ultrasound are based on various types of interferometers. One promising type of interferometer uses real-time holography in a photorefractive material to combine a signal beam that interrogates a vibrating surface with a reference beam for coherent detection. In this configuration, the real-time hologram acts as an adaptive beamsplitter to overlap the wavefronts of the distorted signal beam and the plane-wave reference beam. In spite of their promise, none of the interferometric receivers have performed near their theoretical capability due to limitations in the performance of the photorefractive material. In this Phase I research effort, photorefractive multiple quantum wells with optimized parameters for use as a real-time adaptive beamsplitter in a homodyne interferometer will be designed, grown and characterized. The goals are a low-cost laser ultrasonic receiver with improved signal-to-noise performance and the capability of operating at low light levels. Laser-based ultrasound has applications in a wide range of industrial markets. It offers the capability to improve the inspection rate of existing scanning systems and it will enable the inspection of many parts that can not be tested with other techniques. It is particularly promising as an in-process diagnostic for 100% inspection of mass-produced parts. ***
