Ultrashort pulsed laser backside ablation of fused silica

We report on the fabrication of rectangular microchannels with vertical sidewalls in fused silica by laser backside ablation. A 515 nm femtosecond laser is focused by an objective with a NA of 0.5 through the sample on the glass/air interface, allowing processing from the backside into the bulk material. Experimental investigations reveal a logarithmically increasing depth of the channels with an increasing number of scans, while keeping the focal position fixed. A certain number of scans has to be applied to generate rectangular shaped channels while their depth can be controlled by the applied fluence from 2.64 mu m to 13.46 mu m and a corresponding ablation roughness R-a between 0.20 mu m and 0.33 mu m. The channel width can be set directly via the number of parallel ablated lines demonstrated in a range from 10 mu m to 50 mu m. By adjusting the focal position after each scan the channel depth can be extended to 49.77 mu m while maintaining a rectangular channel geometry. Finally, concentric rings are ablated to demonstrate the flexibility of the direct writing process. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

Rectangular microchannels with vertical sidewalls in fused silica are fabricated using femtosecond laser backside ablation, allowing for control of channel depth and width through applied fluence and number of scans, with focal position adjustment enabling extension of channel depth. The flexibility of the direct writing process is demonstrated by ablating concentric rings.