Low-loss optofluidic waveguides in fused silica enabled by spatially shaped femtosecond laser assisted etching combined with carbon dioxide laser irradiation

We demonstrate the fabrication of low-loss optofluidic waveguides encapsulated in fused silica glass using femtosecond laser microfabrication followed by carbon dioxide laser irradiation. Spatially-shaped femtosecond laser-assisted chemical etching is first used to fabricate microchannels with circular cross-sections and a string of open extra-access ports in the glass. Further, the carbon dioxide laser direct writing on the glass surface is used to create a thermal reflow effect of etched glass microstructures for simultaneously polishing all internal surfaces of channels and sealing the extra-access ports. With this effect, the inner surface roughness of the etched microchannels can be reduced to -40 nm. Finally, a single-mode microfluidic optical waveguide with a propagation loss of -0.78 dB/cm at 1310 nm is obtained inside the glass by filling a mixture solution of decane and liquid paraffin into a laser-polished microchannel.

Automated summary

This paper presents a method for fabricating low-loss optofluidic waveguides in fused silica glass by using femtosecond laser microfabrication and carbon dioxide laser irradiation. Circular microchannels and open extra-access ports are first created using spatially-shaped femtosecond laser-assisted chemical etching. Then, carbon dioxide laser direct writing is applied to achieve a thermal reflow effect, which polishes all internal surfaces of the channels and seals the extra-access ports. By filling a mixture solution of decane and liquid paraffin into a laser-polished microchannel, a single-mode microfluidic optical waveguide with a propagation loss of -0.78 dB/cm at 1310 nm is obtained.