Self-pumped phase conjugation in interferometric detection of laser induced ultrasonic waves on rough surfaces

A well known scheme of the stabilized Michelson interferometer was, used for the detection of laser generated bulk ultrasonic waves to demonstrate the possibiliy of all optical nondestructive material testing, The scheme was improved by a phase conjugate mirror for the possibility of measurements on rough industrial surfaces. Self-pumped phase conjugation in BaTiO3 crystal and subsequent second reflection from the sample surface are used to compensate for the distorted wavefront after the reflection from the sample. Different types of sample surfaces with roughnesses up to 10 mu m were used. The method was used for detection of ultrasonic waves generated via thermoelastic or ablative mechanism.