2. Laser Induced Damage Threshold – LIDT

Laser Induced Damage Threshold (LIDT) is a physical characteristic of optical component which defines a critical power or peak fluence of laser irradiation causing irreversible changes in materials structure. There exist several (application dependent) interpretations of this definition.

Technical definition: Laser-Induced Damage Threshold is the ability limit of material to withstand intense laser irradiation without observable changes in its optical properties.

International standard ISO 21254-1, 2, 3 and 4 definition: Laser-induced damage threshold is the highest quantity of laser radiation incident upon the optical component for which the extrapolated probability of damage is zero where the quantity of laser radiation may be expressed in energy density, power density or linear power density. LIDT is often confused with Ablation Threshold (interpreted as a laser melting or evaporation point) which is not the same.



Q: If I am very close to the damage threshold but below it is it safe for my optics?

A: It is not recommended to operate very close to the damage threshold since it depends on many things. Depending on material, wavelength, rep. rate, environmental properties, coating type and other factors LIDT may change in time. Use operating fluence preferably below 50% of the damage threshold.