Femtosecond-laser-written optofluidics in alumino-borosilicate glass

Femtosecond Laser Irradiation followed by Chemical Etching (FLICE) is a powerful technique for prototyping three-dimensional microfluidic structures in glass. Direct inscription of optical waveguides, by the same femtosecond laser, enables rapid fabrication of optofluidic devices for chemistry or biology applications. As a matter of fact, substrates where FLICE is known as most effective, such as fused silica, are not optimal for laser inscription of high-contrast optical waveguides, thus limiting the potentials of this technology. Here we show that it is possible to apply FLICE also to a commercial alumino-borosilicate glass, where very complex and low-loss photonic circuitry has been demonstrated recently. Besides optimizing the irradiation parameters to achieve hollow structures with high aspect-ratio, we investigate the etching dynamics and the micro-morphology of the etched regions. As a test for the technique, we realize an optofluidic device composed of a microchannel and two intersecting optical waveguides. •Selective etching of femtosecond-laser-written tracks in borosilicate glass.•Etching mechanism shows differences from analogous process in fused silica.•Optical waveguides and microchannels are integrated in a borosilicate-glass chip.