Dielectric Mirror Damage by Laser Radiation over a Range of Pulse Durations and Beam Radii

Laser induced damage characteristics have been studied for twelve, multiple-layer dielectric, 95% reflecting mirrors irradiated with single ruby laser pulses of 20 nsec and 20-psec duration and Gaussian beam radii ranging from 0.06 mm to 0.24 mm. During measurements to determine damage threshold the pulse energy, an oscilloscope trace of the pulse, and the beam's transverse energy density profile at the surface being damaged are recorded for each shot. In a separate set of experiments, the temporal development of coating breakup and plasma formation is investigated. The experimental results are discussed in the context of possible damage mechanisms.