Fabrication and performance analysis of on-chip optical whispering-gallery mode resonators for dynamic thermal sensing

Due to the small mode volume, high quality factor (Q-factor), and micro- nano- size of optical whispering-gallery mode (WGM) resonators significant interest in potential applications in physics and engineering for WGM based photonic devices has been generated. In the past two decades, studies have been conducted demonstrating the capabilities of WGM sensor devices for biological, chemical, pressure, and temperature sensing among other fields. These studies often demonstrate the high-resolution capabilities of optical WGM micro-sensors, however, the actually sensing device was an independent component in the system it was monitoring. In the present dissertation, methods for the fabrication of optical WGM sensor onto a region of interest are discussed. These techniques allow the WGM devices to achieve, for the first time, direct, on-chip, measurement capabilities, allowing them to take full advantage of their small size and high resolution. In particular, techniques are developed for the fabrication of silica based glasses and polymer based resonator onto an electrical working component. These fabrication methods allow for both cylindrical annulus and ellipsoid shell geometries with Q-factors as high as 106. Use of polymers allow for low-cost fabrication of sensors without risking thermal damage to the electronic component. These devices are also evaluated for potential use as temperature sensors at both room and cryogenic temperature regimes. The theory for WGM temperature sensitivity is developed to explain the diameter dependence of a dielectric coating on a conductive core. The design and fabrication of two experimental setups capable of creating controllable temperature environments are discussed. The first of these setups can be used to create a stable temperature environment at room temperature to 10K above room temperature. The second setup is designed for WGM testing below 100K. Within these experimental setups WGM sensors are calibrated in their respective temperature regimes. PDMS is shown to be able to support WGM resonance below 100K for the first time. The calibrated sensors are also evaluated against both thermocouples and heat transfer theory for the real-time temperature monitoring of the core wire as it undergoes Joule heating. The performance of the sensor is discussed in detail for both temperature regimes. Additionally, a preliminary exploration of the potential use of WGM sensors for the temperature monitoring of superconducting wires is performed.Ph.D.Includes bibliographical referencesby Matthew Frenke