Fabrication of polarization-independent microchannels in fused silica using shaped femtosecond laser-assisted etching

The Femtosecond Laser-assisted Etching (FLAE) technique represents an optimal approach for fabricating three-dimensional microfluidic channels. In this study, we introduce a novel approach utilizing birefringent crystals for temporal and polarization shaping to generate orthogonally polarized pulse sequences, effectively controlling the polarization dependence of the etching process, and achieving high-precision and high-efficiency microchannel fabrication in fused silica. Experimental results demonstrate that polarization-independent etching can be achieved by manipulating the sub-pulse delays and polarization states. Additionally, we found that four-pulse sequences offer a higher etching rate compared to dual-pulse sequences under the same conditions, thus enhancing manufacturing efficiency. Incorporating slit beam shaping on top of temporal and polarization shaping has successfully adjusted the longitudinal and transverse dimensions of the microchannels, improving their cross-sectional roundness and quality. Overall, we propose a method for fabricating polarization-independent microchannels and optimizing their cross-sectional profiles.