F_2-laser microfabrication of sub-μm gratings in fused silica

摘要

Submicron surface-relief gratings were fabricated on fused silica by laser ablation with nanosecond (ns) pulses from a high-resolution F_2-laser processing station. The grating relief was generated by imaging a transmission amplitude grating with a Schwarzschild objective of 25x demagnification. The chrome-coated CaF_2 mask had been structured by laser ablation at 193 nm to form a line and space pattern of 20-μm period. The F_2-laser generated gratings on fused silica were characterized by SEM, AFM and diffraction of a HeNe laser beam, yielding a grating period of 830 nm and a corrugation depth of 250 nm. Surface-relief gratings on optical materials are required for various applications such as grating demultiplexers for telecommunication components, light couplers for planar optical waveguides, Bragg reflectors, or alignment grooves for liquid crystals. Laser ablation is a rapid and flexible method to generate custom grating designs on a variety of materials.