Microchannels fabrication in nanoporous silicate matrix by femtosecond direct laser writing and subsequent chemical etching

Femtosecond direct laser writing (FDLW) is a powerful tool for modification of the properties of transparent materials through nonlinear multiphoton absorption. Implementing such a tool makes it possible to fabricate buried optofluidic elements for microfluidic (MF) systems and optical waveguides in glass materials. In this study a novel method for microchannel fabrication in glass was suggested. Microchannels were fabricated by FDLW in two-phase glass followed by chemical etching. We report two types of laser modification of two-phase glass processed material with pronounced refractive index change, and core-cladding-like elements that include a densified core surrounded by a decompressed region and an outer densified shell. Fabricated microchannel prototypes resulted from applying different pulse durations, each with various laser powers and scanning speeds. Chemical etching of two-phase glass in HCl is a procedure to obtain a nanoporous matrix and to clean out the channels. After chemical etching both types of modification resulted in similar microchannels with different width and layer properties. Highly uniform microchannels with high aspect ratio, and a pronounced refractive index surrounding layer were achieved after chemical etching, which could possibly be used as waveguide layers.