Repetitively pulsed laser damage in optical thin films

摘要

The theory of laser-induced damage in dielectric films, containing highly absorbing impurities, developed previously for single-shot damage is extended to the case of multiple shots. Calculations are carried out for micro-, nano-, and pico-second pulses, with the time interval between pulses varying from equal to the pulse duration to two-orders of magnitude greater than the pulse duration. It is found that in the case of spherical impurities the size of the easiest to damage particle is in general a complicated function of the laser intensity, pulse duration, and time interval between pulses. However, for sufficiently large number of pulses, the dependence is much simpler, characterized by constant values of the following: (1) pulse duration multiplied by the number of shots divided by the square of the radius of the easiest to damage impurity; (2) the minimum intensity needed to cause damage multiplied by the radius of the easiest to damage impurity.