Sensing with Optical Microresonators and Integrating Cavities

Abstract

This thesis explores theoretical and experimental considerations for the design of refractometric sensors based on optical microcavities for sensing of gases and liquids as well as integrating sphere laser absorption spectroscopy for the detection of greenhouse gases. I discuss highly sensitive refractometric sensing of fluids using a robust, inexpensive platform consisting of a cylindrical microcapillary and broadband light source. Next, I adapt this platform for performing refractometric sensing with the hitherto little-explored "star" and "triangle" modes of microcapillaries. When pumped with sufficient intensity, these modes are capable of lasing and demonstrating high sensitivity to the refractive index of fluids in the capillary channel. This lasing refractometric sensor is then demonstrated for the detection of carboxy-functionalized polystyrene microspheres binding to the inner capillary wall. Finally, I discuss the benefits of using integrating spheres in laser absorption spectroscopy of methane and carbon dioxide, and demonstrate detection of single-digit part-per-million quantities of methane.