doi:10.3850/978-981-08-6555-9_157

ABSTRACT

Femtosecond laser machining is a versatile materials processing technology suitable for fabricating a wide range micro- and nanostructures. Nondiffracting zero-order Bessel beams enable to answer two problems of ultrafast laser micromachining. First, in the case of surface laser nanostructuring, threshold effect allows for creating craters below the spot size but at cost of critical sample positioning. The long focal zone of Bessel beams render sample positioning non-critical. Ultrafast laser micromachining holds particular promise for microfluidics applications where high quality sub-10 µm channels are essential structures in the development of system-scale lab-on-chip and DNA analysis. Femtosecond microchannel machining in various glasses has been the subject of many previous studies and, whilst debris redeposition and tapering effects precludes high aspect ratio microchannel fabrication using simple front-surface illumination in air, several more sophisticated approaches have been developed. These include micromachining in vacuum, micromachining with filamentary propagation, micromachining combined with selective etching, and micromachining the reverse side of the sample using water immersion for debris removal. These previous studies, however, have all used femtosecond lasers with transverse Gaussian beam intensity profiles. In this paper, an alternative and original approach is described using high-aspect ratio Bessel beams to overcome many of the difficulties associated with femtosecond micromachining with Gaussian beams.

Microchannels with aspect ratio 40 and diameter 2 µm can be drilled in glass without sample translation.

Keywords: Ultrafast laser material processing, Nondiffracting beams.

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