Ultrafast and precision processing of glass by selective absorption of fiber-laser pulse into femtosecond-laser-induced filament

The extreme intensity of femtosecond laser pulses can enable microfabrication in glass. However, conventional femtosecond laser based glass processing has two severe limitations, viz., a low processing speed and the generation of damage during processing. To create a hole with a diameter of 10 mu m and a depth of over 100 mu m using the conventional method, hundreds of pulses must be focused on a single spot because the volume removed by a single femtosecond laser pulse is too small. Furthermore, whenever a laser pulse is focused on the target surface, a strong stress wave is generated, thereby hindering precision. We have resolved these issues by coaxially focusing a single femtosecond laser pulse and a fiber laser pulse having a wavelength that is transparent to glass. A hole with a diameter of 10 mu m and a depth of 133 mu m was created in 40 mu s, which indicates that the processing speed was over 5000 times faster than that of a conventional femtosecond laser. Moreover, the damage generated was considerably eliminated in comparison with the conventional method, and precision processing was achieved. The results of this study will help expand the industrial applications of femtosecond laser processing.