紫外光学薄膜の多光子吸収と電子雪崩の観測

抄録

Non-linear absorption was measured for optical thin layers of various oxides and fluorides by using 1.7 ps and 20 ns pulses of a KrF laser. Laser induced damage due to two-photon absorp-tion was detected in oxide coatings by photo-acoustic measurement. In fluoride films, three photon absorption was less than linear absorption up to their damage threshold around 600GW/cm². We measured photo-current in the films to detect dynamic absorption within nanosecond irradiation. A nonlinear current growth due to electron avalanche was observed. The damage thresholds were found to be correlated inversely with the carrier lifetime of coatings.