Polarization-independent selective etching of fused silica glass induced by femtosecond laser pulses in GHz burst mode

Polarization-independent ultrafast laser-induced selective etching (ULISE) using GHz femtosecond laser bursts is demonstrated in fused silica. Its performance at various inscription conditions was studied, revealing a high etching speed (>600 µm/h) and a lower nonlinear threshold. Complex 3D microchannel networks and 2D curved microchannels were successfully fabricated. Unlike conventional femtosecond laser pulses that form polarization-dependent nanogratings or sparse nano cracks in the “few-pulse” regime, GHz femtosecond laser bursts generate random micro/nano cracks and eliminate polarization dependence, similar to those induced by picosecond lasers with pulse duration ≥4 ps. This technique offers a new strategy for high-throughput, high-fidelity 3D subtractive manufacturing of brittle glass and crystals.