Micro- and nano-structured optically functional surface textures continue to exhibit higher performance and longer term
survivability than thin-film coatings for an increasing number of materials used within high energy laser (HEL) systems.
Anti-reflection (AR) microstructures (ARMs) produce a graded refractive index yielding high transmission over wide
spectral ranges along with a chemical, mechanical and laser damage resistance inherited from the bulk optic material.
In this study, ARMs were fabricated in the relevant HEL materials sapphire, neodymium-doped YAG, fused silica, BK7
glass, and the magnesium aluminate known as SPINEL. Standardized pulsed laser induced damage threshold (LiDT)
measurements were made using commercial testing services to directly compare the damage resistance of ARMs-treated
optics to uncoated and thin-film-AR-coated (TFARC) optics at wavelengths of 532nm, 694nm, 800nm, 1064nm, and
1538nm. As found with prior work, the LiDT of ARMs etched in fused silica was typically in the range of 35 J/cm2 at a
wavelength of 1064nm and a pulse width of 10ns, a level that is comparable to uncoated samples and 3.5 times greater
than the level specified by six prominent TFARC providers. The Army Research Laboratory measured the pulsed LiDT
at 532nm (10ns) of ARMs in fused silica to be up to 5 times the level of the ion beam sputtered TFARC previously
employed in their HEL system, and 2 times higher than a low performance single layer MgF2 TFARC. This result was
repeated and expanded using a commercial LiDT testing service for ARMs in two types of fused silica and for Schott
N-BK7 glass. An average damage threshold of 26.5 J/cm2 was recorded for the ARMs-treated glass materials, a level 4
times higher than the commercial IBS TFARCs tested.