High-speed and crack-free direct-writing of microchannels on glass by an IR femtosecond laser

•Optimal processing modes were defined at high-speed fs laser ablation of BK7 glass.•An automated inspection technique was developed to extract quality characteristics.•The value of roughness is minimal when multi-pass machining is performed.•The regression model was appropriate to fabricate microchannels with accuracy of 5%.•The productivity higher than 0.3 mm3/min was obtained without post-processing.

Fabrication of high-resolution 3D structures with laser radiation on the surface of brittle materials has always been a challenging task. Even with femtosecond laser machining, micro-cracks and edge chipping occur. In order to evaluate processing modes optimal both in quality and productivity, we investigated high-speed (50 kHz) femtosecond laser processing of BK7 glass with the use of design of experiments and regression analysis. An automated inspection technique was developed to extract quality characteristics of test-objects. A regression model was obtained appropriate to fabricate microchannels with a predefined depth in the range of 1–30 µm with average accuracy of 5%. It was found that high quality machining modes are in the range of 0.91–2.27 µJ energy pulses, overlap of 53–62%, three and more number of passes. A material removal rate higher than 0.3 mm3/min was reached and microfluidic structures were formed based on data obtained.