Femtosecond laser micromachining of suspended silica-core liquid-cladding waveguides inside a microfluidic channel

This work addresses the fabrication of straight silica-core liquid-cladding suspended waveguides inside a microfluidic channel through fs-laser micromachining. These structures enable the reconfiguration of the waveguide's mode profile and enhance the evanescent interaction between light and analyte. Further, their geometry resembles a tapered optical fiber with the added advantage of being monolithically integrated within a microfluidic platform. The fabrication process includes an additional post-processing thermal treatment responsible for smoothening the waveguide surface and reshaping it into a circular cross-section. Suspended waveguides with a minimum core diameter of 3.8 mu m were fabricated. Their insertion losses can be tuned and are mainly affected by mode mismatch between the coupling and suspended waveguides. The transmission spectrum was studied and it was numerically confirmed that it consists of interference between the guided LP01 mode and uncoupled light and of modal interference between the LP01 and LP02 modes.

Automated summary

This work focuses on the fabrication of straight silica-core liquid-cladding suspended waveguides using fs-laser micromachining in a microfluidic channel. The waveguides are further smoothed and reshaped into a circular cross-section through post-processing thermal treatment. The study shows that the suspended waveguides have adjustable insertion losses and allow for the reconfiguration of the mode profile, enhancing the evanescent interaction between light and analyte.