Formation of Bottom Conjugate Pair Grooves by Femtosecond Laser Grooving on Transparent Substrate

Ultrashort pulsed laser is a promising tool for processing transparent materials. We report on a new approach that simultaneously creates a pair of conjugate grooves on the bottom surface of a thin glass substrate at the duration of plowing a V-shaped microgroove on the top surface using the technique of direct laser ablation. We propose a hypothesis to explain the accompanying grooves' formation mechanism and simulate Maxwell's equations to verify its applicability. Measurements showed the surface roughness of the groove's sidewalls was 0.14 μm. This method requires no mask, can be directly performed in the atmosphere, and can simultaneously produce microgrooves on both sides of the substrate that render it an effective approach for producing high quality V-shaped microgrooves on both sides of the substrate.