The performance requirements of optical coatings are closely related to their specific applications. Different fields, different systems, and different application environments impose different performance requirements on optical coatings. The laser-induced damage threshold (LIDT) is the ultimate indicator of a laser coating's 'tolerance,' referring to the maximum laser energy density that the coating can withstand without experiencing permanent damage (such as melting, peeling, or cracking of the coating). Since the damage mechanisms of continuous wave lasers and pulsed lasers are completely different, their requirements for the LIDT of filters are fundamentally distinct. Optical coatings used in high-power laser systems have outstanding requirements for having sufficiently high damage thresholds.

With changes in laser wavelength, pulse width, structure, and repetition rate, the damage mechanisms of thin films and the corresponding control and improvement methods can vary greatly. The thin films required for high-power laser systems mainly include high-reflection films at different angles, anti-reflection films, polarizing films of various sizes, beam-splitting films with specific intensity ratios and polarization ratios; frequency-doubling films for different harmonics and requirements, as well as various wavelength-separation films.