Conical Phase Front And Aberration Beam Shaping For Manipulating Femtosecond Laser Chemical Etching

The countering and enhancing influence of surface aberration in combination with conical phase front beam shaping was examined over shallow to deep focusing inside of fused silica to facilitate the geometric control of chemical etching tracks formed by femtosecond laser inscription. The tuning of the collective shaping effects is shown to compensate for a wide focusing range to favorably manipulate the chemical etching rate, the resolution, the surface roughness, and the cross-section profile of the resulting micro-channels. Using only a single laser scanning track, micro-channels have been tailored from symmetrical to highly asymmetric cross-section of up to 1:13 aspect ratio, permitting distortion-free processing to depths of 1.5 mm. The combined shaping effects thus expand the utility of laser chemical etching for micromachining of transparent substrates.