Laser-induced damage properties of antireflective porous glasses

Porous nanostructures on BK7 glass manufactured by chemical treatment are able to function as antireflection (AR) components over a wide spectral range and have potential to achieve high laser damage resistance. The damage-resistant properties of antireflective porous glasses with nearly 100% transmittances exposed to pulse lasers with three different central wavelengths were investigated in this paper. The laser damage tests showed that the LIDTs under the irradiation of 12 ns 1064 nm pulses, 10 ns 532 nm pulses and 8 ns 355 nm pulses are 58 J/cm(2), 20 J/cm(2) and 12 J/cm(2), respectively. These values are much higher than those of AR coated glasses, but are almost the same level of un-etched substrate. To understand possible damage mechanisms, the role of electric field distribution inside the porous structure during the laser radiation process was investigated by a three-dimensional finite difference time-domain method. The temperature distribution resulting from the internal electric field may be a main factor to induce the damage. In addition, the involved defects during the etching process are also responsible for the damage in the porous structure. Finally, some possible approaches to improve the LIDT are proposed. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.