  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.
