Manufacture of Three-Dimensional Optofluidic Spot-Size Converters in Fused Silica Using Hybrid Laser Microfabrication

We propose a hybrid laser microfabrication approach for the manufacture of three-dimensional (3D) optofluidic spot-size converters in fused silica glass by a combination of femtosecond (fs) laser microfabrication and carbon dioxide laser irradiation. Spatially shaped fs laser-assisted chemical etching was first performed to form 3D hollow microchannels in glass, which were composed of embedded straight channels, tapered channels, and vertical channels connected to the glass surface. Then, carbon dioxide laser-induced thermal reflow was carried out for the internal polishing of the whole microchannels and sealing parts of the vertical channels. Finally, 3D optofluidic spotsize converters (SSC) were formed by filling a liquid-core waveguide solution into laser-polished microchannels. With a fabricated SSC structure, the mode spot size of the optofluidic waveguide was expanded from similar to 8 mu m to similar to 23 mu m with a conversion efficiency of similar to 84.1%. Further measurement of the waveguide-to-waveguide coupling devices in the glass showed that the total insertion loss of two symmetric SSC structures through two similar to 50 mu m-diameter coupling ports was similar to 6.73 dB at 1310 nm, which was only about half that of non-SSC structures with diameters of similar to 9 mu m at the same coupling distance. The proposed approach holds great potential for developing novel 3D fluid-based photonic devices for mode conversion, optical manipulation, and lab-on-a-chip sensing.

Automated summary

We propose a hybrid laser microfabrication approach for the manufacture of three-dimensional optofluidic spot-size converters. The method combines femtosecond laser microfabrication and carbon dioxide laser irradiation to create complex microchannel structures in glass and achieve size conversion by filling them with liquid-core waveguide solution. Experimental results demonstrate high conversion efficiency and low insertion loss of this method.