Infrared laser-induced desorption of H2O and hydrocarbons from optical surfaces

Abstract

Laser-induced desorption has been demonstrated for strongly optically absorbing molecules on nominally transparent substrates. Both H2O and hydrocarbon contaminants were desorbed using a pulsed HF/DF laser source at 2.8 and 3.7 μm. Following laser desorption of H2O, the 2.8-μm damage threshold in CaF2 roughly doubled. Surface mapping of H2O desorption with a 120-μm-diam focal spot showed considerable variation with spatial position on polished CaF2, indicating localized concentrations of adsorbate.