Optimization of fs + ps double-pulse sequence parameters for laser-assisted chemical etching of microchannels in fused silica

Abstract

Developing laser fabricating technology to improve the etching rate of microchannels is of great significance for the development of microfluidic devices. In this paper, the laser processing parameters of the fs + ps double-pulse sequence, including temporal delay and pulse energy ratio, have been investigated to optimize the fabrication of microchannels, in order to obtain a high etching rate. As a result, the optimal energy ratio could be obtained at Efs:Eps = 2:1 in negative delays. Furthermore, the etching rate of microchannels was significantly improved by 40.8% compared with those written by fs + fs double-pulse sequence with an energy ratio of 1:1. This improvement is possibly because fs sub-pulse excited seed electron may trigger impact ionization via an efficient energy absorption process within the following ps sub-pulse, this energy accumulation and subsequent thermal diffusion lead to an increase of the modified area. The aforementioned results possibly offer an effective route to improve the etching rate of microchannels which is in favor of accelerating the fabrication of three-dimensional microfluidic devices.