http://www.jlps.gr.jp/jlmn/index.php?action=laser_volno&volno=203

A two-grating interferometer setup is described for fabricating large area grating structures via laser ablation with UV femtosecond pulses. Phase grating pairs on fused silica substrates with high damage threshold and diffraction efficiency were illuminated with non-collimated (convergent) laser beams to generate a periodic intensity distribution with high energy density and high contrast on the sample surface. Large line numbers without phase distortions were reached by applying cylindrical focusing perpendicular to the grating lines. Scanning the illuminating laser beam in the direction parallel to the grooves enabled the fabrication of cm-scale grating sizes with multiple shot ablation, while keeping the whole line structure in phase. Complex patterns are possible by applying multiple exposures. Experimental results demonstrating the capability of the method to generate laser ablated grating structures with submicron periods down to ~300 nm are presented.