Microstructuring of Transparent Dielectric Films by TWIN-LIBWE Method for OWLS Applications

We report on the fabrication of micro-and submicrometer period transmission gratings in SiO 2 , Al 2 O 3 , and Y 2 O 3 thin films by two-beam interferometric laser-induced backside wet etching (TWIN-LIBWE). The optimal etching parameter domain has been established for each film with the help of profilometric and atomic force microscopic measurements. The modulation depth and the quality of the etched SiO 2 film is found excellent over a relatively broad fluence (285-600 mJ/cm 2 ) and pulse quantity (1-150) range. For Al 2 O 3 , and Y 2 O 3 films it is significantly narrower (250-260 mJ/cm 2 and 1-10 pulses). We have tested the created gratings as waveguide couplers, which prove the suitability of the studied method to produce transmission gratings onto dielectric films.