Homodyne detection of ultrasonic surface displacements using two-wave mixing in photorefractive polymers

Summary form only given. Laser-based ultrasound is a promising technique for remote ultrasonic inspection. One approach for the measurement of small ultrasonic surface displacements uses dynamic holography in a photorefractive material to combine a distorted signal beam with a plane-wave reference beam and match their wavefronts for homodyne detection. Slow variations in the wavefront of the signal beam are compensated by the real-time hologram and thus do not produce noise or interfere with the quality of the wavefront overlap in the output beams.