Femtosecond Laser Engraved 2D Tunable Optofluidic Liquid Core/Air Cladding Channel Waveguides on PDMS

Abstract

We have demonstrated the fabrication and characterization of 2D liquid-based multimode optical waveguide structures over a Polydimethylsiloxane (PDMS) material-based chip. Fabrication of two separate microstructures, one with a width of 14 microns and a depth of 27 microns while the other with a width as well as depth of 110 microns, was achieved by the femtosecond laser micromachining process. The dye solution is passed through the microstructure from one end to the other; wherein the dye solution acts as the core while PDMS and air act as the cladding medium. The femtosecond laser micromachining parameters are optimized in terms of laser power, pulse width, writing speed, focused beam size, etc. The quality of fabricated microstructures is confirmed by microscopic analysis. The confirmation of liquid-core/air cladding-based waveguide is obtained through spectral and modal analysis. The optical analysis has been done by using fluorescence light coupled out from waveguide structures filled with different dye solutions. These waveguide structures give strong light confinement and intense interaction between dye solution and pump light. The developed microstructures are tunable in terms of intensity, wavelength, and beam size. Such microstructures can be implemented in the design and development of lab-on-chip microlasers and sensing applications in any multifunction lab-on-chip devices.