Preliminary Experimental Results of Spot Size Scaling in Laser Induced Damage to Optical Coatings
SourceThe laser damage threshold of various thin film coatings has been assessed using 1.06 μm radiation at a pulse length of 6ns FWHM. Samples of conventional coatings of several materials have been tested as a function of film thickness and spot size. Beam diameters employed range from approximately 9μm and larger.
From these preliminary data, previously observed scaling has been verified, i.e., thinner films are more damage resistant, while smaller spot sizes yield higher damage thresholds, as expected. The samples employed in these tests were conventional coatings of ThF4, ZrO2 and HfO2 as well as specially prepared “Low defect” coatings of Cerac and RAP grown ThF4. These “low defect” coatings are initial efforts and unfortunately showed no advantage over conventional coatings in terms of damage threshold.