Design and modelling of integrated photonic devices for sensing and switching applications

In this work, we describe the design and modeling of integrated photonic devices based on photonic waveguides on silicon substrates. We have first designed and modeled integrated photonic chemical sensors, in which the sensing region is integrated with the on-chip optical waveguides that carry the light to and from the sensing regions, such that the transduction in the light signal due to the presence of the analyte molecules could be detected. This work involves the designing and modeling of micro-scale to nano-scale optical waveguides of silicon on insulator substrates as well as silicon nitride waveguides on thermal oxide in silicon substrates. The optical waveguides are integrated with nanophotonic structures developed on the sensing regions. We are employing numerical modeling methods such as FDTD, FDFD, and FEM to simulate these integrated sensor devices. The fabrication of these sensor devices is also being carried out. We have also designed and modeled integrated switches based on Phase-Change Materials (PCMs). We investigate hybrid device architectures utilizing the non-volatile properties of PCMs for integrated programmable photonics in a Si₃N₄ platform. FDTD modeling was carried out to study configurations of reconfigurable switches such as a reconfigurable reflector switch consisting of a photonic crystal slab waveguide and having a thin layer of PCM on top of the waveguide and a 1×2 mode converter switch. In the case of a non-volatile reconfigurable reflector switch, the reflectivity of the waveguides is controlled by shifting the mode-gap of the photonic crystal slab waveguide by changing the phase of the PCM.