Design and Development of Optical Waveguide Architectures for Real-Time Temperature Monitoring in Extreme Environments

This dissertation prompts on the research and development of a new real-time, reusable, and reversible optical sensor for integrated temperature monitoring in harsh environments. This is achieved through integrating the photonic properties of optical waveguides/optical fiber and the phase change properties of chalcogenide glasses (ChGs). ChG materials have very specific crystallization temperatures beyond which these materials transform from being a dielectric material to a metallic material. When such ChG material is coated over a dielectric optical waveguide, in the crystalline phase, highly localized surface plasmon polariton (SPP) modes are generated at the waveguide: metallic ChG interface. In this case, the modes are characterized by very large propagation losses compared to that when the ChG is in its amorphous phase. By monitoring the output power in the two different phases of ChG, ambient temperature can be determined. In ChG materials, the crystalline state of ChGs can be reverted back to its initial amorphous condition through the application of a short intense voltage pulse that melts the material, facilitating multiple time use of the sensors. Based on the phase change property of ChG glasses, and light confinement offered by optical waveguides, we proposed to construct two types of sensor architectures for sensing temperature:Architecture 1: An optical fiber based reflection mode sensor. Architecture 2: An integrated silicon waveguide:ChG based compact plasmonic temperature sensor. These sensors are typically suitable for the real-time monitoring of component temperatures up to 500 ˚C, although with specific adjustment of the composition of the ChG material, these sensors can become useful for metallic or ceramic SFR reactors where the cladding temperature can reach 650 ˚C. This will provide a temperature monitoring method for multiple components in the reactor design domain of multiple reactors. It can be further employed as in a number of hybrid electron/photonic tandem ChG/Si solutions (for example, when non-volatile memory is necessary to be introduced based also on the phase changes in the ChG) in the nuclear facilities since the chalcogenide glasses are radiation hard materials.