Ultrasonic Technology for Characterizing Laser Damage in Optics

An ultrasonic technique was developed to detect and characterize laser damage in critical optics. During normal usage, sub critical flaws induced by high laser fluence can grow to critical size and potentially can cause unanticipated failure of the optics. This ultrasonic technique monitors the optic in situ and provides a quick, reliable way to quantify the location, number and, ultimately, the size of defects that may initiate and grow during firing of the laser. The feasibility of detecting and sizing laser-induced damage with an ultrasonic technology was theoretically and experimentally demonstrated. An experiment was conducted whereby ultrasonic data was acquired in situ on an optic as it was damaged by a laser. This monitoring of laser induced damage clearly demonstrated the potential for ultrasonic monitoring of critical optics for laser-induced damage.