Damage and its mechanism to the visible wavelength filter irradiated by femtosecond laser: Damage and its mechanism to the visible wavelength filter irradiated by femtosecond laser

The mechanism of damage to the optical coatings of filters induced by femtosecond laser at different wavelengths was studied. A near infrared wavelength tunable femtosecond laser was used to rediate the visible wavelength filter from backside. The wavelengths were selected in the transitional region of the filter pass band and the corresponding threholds of average power density were obtained. Based on the avalanche ionization process, the relationship between damage threshold and distribution of interference field was investigated. The theoretical results can predict the trend of thresholds. The results indicate that the damage behavior of a coating irradiated by femtosecond laser pulses exhibits an overall behavior. The damage threshold decreases with the increase of transient residual energy in the multi-layer structure of the coating.