Modeling of optical wavguides with porous silica claddings and their use in LEAC sensors

Abstract

Integrated optical biosensors have many advantages such as low-cost, portability and the ability to detect multiple analytes on a single waveguide. They can be used in many important applications including biosensing applications. Previous research work focused on the issues of design, modeling and measurement of the local evanescent array coupled (LEAC) biosensor. The sensors were made using conventional dielectrics such as SiO2 and SiNx. The large increase in the complexity of the integrated circuits has increased the need for developing low-k dielectrics as new materials to cope with the integration challenges and improve operating speed. Furthermore, optical interconnects are required to be used to replace electrical interconnects in ICs to meet future goals. This increases the need for simultaneous manufacturing of electronics and optics on the same chip using a CMOS process. The research conducted during my Master of Science studies has addressed two important goals. The first was to use models to calculate surface and volume scattering losses in optical waveguides, especially, ones with porous silica claddings. The second goal was to use the simulation results to demonstrate the possibility of using porous silica in designing optical waveguides and LEAC sensors. By applying these models to porous silica optical waveguides described in previous publications, the agreement between their experimental results and the models results have been proved. Thus, these models can be used in the future to calculate the scattering losses in optical waveguides including ones with porous silica cladding. The main methods that are used to prepare porous silica and the models that are used to determine the effective index of porous silica have been discussed. A Matlab modesolver was used to simulate porous silica waveguides. Predictions for sensor sensitivity and waveguide loss as a function of waveguide dimension have been made using modesolver simulation results. The results demonstrate the ability to use porous silica in LEAC sensors in the future.