Employing SiO2 buffer layer to improve adhesion of the frequency-doubled antireflection coating on LBO

Frequency-doubled antireflection coatings simultaneously effective at 1064 nm and 532 nm were deposited on the lithium triborate (LiB3O5 or LBO) crystals using the electron beam evaporation method. Comparing with the sample without buffer layer, it is found that the adhesion of the sample with buffer layer of SiO2 between coating and LBO substrate is improved significantly from 137.4 mN to greater than 200 mN. And the laser-induced damage threshold is increased by 20% from 15.1 J/cm(2) to 18.6 J/cm(2). The strengthening mechanism of adhesion of the buffer layer of SiO2 is discussed by considering full plastic indentation and shear theory.