Design and experimentation of liquid-liquid waveguides

Abstract

This report investigates the parameters affecting the output light intensity given a fixed input light intensity through a liquid-liquid waveguide made from poly(dimethylsiloxane) (PDMS) material. In the biomedical industry, since most biological samples are in forms of liquid solutions, there is reason for research to be carried out more with liquid-liquid waveguides. Moreover, liquid waveguides have been known to have lower interfacial loss compared to solid waveguides, hence the growing interest in investigating liquid-liquid waveguides. At a micro scale level, flow of liquid is laminar. Because liquid-liquid waveguides are dynamic, parameters can be adjusted accordingly to specific user-requirements. For the straight waveguide, 3 parameters are of concern in this report: The refractive index of the core, the refractive index of the cladding and the core width. Every other factor is held constant when one of these is changed. For the curved waveguides, 2 additional parameters are of concern: The sweep angle and the radius of curvature. The results of the experiments are shown to be very close to the actual theoretical concepts of waveguides as studied by previous researchers. Reasons for the differences in detected output light intensity can also be explained through the various losses that occur in liquid-liquid waveguides. Losses in straight and curved liquid-liquid waveguides are also compared with theoretical results and explained.