Fabrication of millimeter-scale deep microchannels in fused silica by femtosecond laser filamentation effect

In this work, a millimeter-scale deep microchannel is processed in 2 mm thick fused silica using direct punching based on the femtosecond laser filamentation effect. The length of the femtosecond laser filament, the position and the time of interaction with the material were adjusted by changing the laser power, focus position and processing time. The variations of depth and opening diameter with different laser parameters were further analyzed under linearly polarized light and circularly polarized light. The results show that in the negative defocusing state (＜2 mm), the depth of the microchannel increases and the opening diameter of the microchannel remains almost unchanged as the defocusing distance increases. Compared with the microchannel processed by linearly polarized light, the microchannel processed by circularly polarized light has a larger depth and a smaller diameter under the same parameter combination. The influence of polarization state on microchannel opening roundness and bottom morphology was analyzed. The possible influencing mechanisms of femtosecond laser processing microchannel were elucidated. Based on this, the optimum combination of parameters for processing millimeter-scale deep-microchannels in fused silica was obtained. Therefore, this work would be helpful for the application of fused silica materials in microchannels.