InGaAsP-InP Semiconductor Microcavity Geometries for Annular Bragg Reflection, Optical Switching, and Sensing

Citation

Green, William M. J. (2005) InGaAsP-InP Semiconductor Microcavity Geometries for Annular Bragg Reflection, Optical Switching, and Sensing. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/GGH2-AQ53. https://resolver.caltech.edu/CaltechETD:etd-05292005-111904

Abstract

One of the key mandates of modern optoelectronic research is the development of compact photonic integrated circuits, capable of performing many diverse functions for the generation, manipulation, and detection of light, all on a single chip. A key practical requirement for such circuits is the development of optical devices for the localization and processing of light within extremely small dimensions. In recent years, planar microring and microdisk resonators, in which light is confined by total internal reflection, have emerged as versatile photonic elements for filling this role. The high quality factors and long photon storage times associated with the whispering-gallery modes supported by these microcavities result in several technologically useful characteristics, including narrow-band filter response, and large resonant enhancement of the circulating electric field. These properties have been exploited in numerous passive and active device applications, including optical add/drop multiplexers, all-optical switches, and tunable lasers.

This thesis describes the study of several unique ring-based optical microcavity geometries based upon the indium gallium arsenide phosphide/indium phosphide alloy semiconductor material system, undertaken in an effort to explore new optoelectronic architectures for confining and manipulating light.

The first portion of this work involves the analysis and demonstration of a new microcavity geometry, in which cylindrical Bragg reflection is used for radial optical confinement, as an alternative to total internal reflection. In this class of structures, collectively known as annular Bragg resonators, light can be guided within a ring or pillar defect layer surrounded by cylindrical Bragg mirrors. Several microcavities based upon this configuration are designed and fabricated using a thin InGaAsP quantum well membrane. Using pulsed optical excitation, the characteristics of these structures as low threshold vertically emitting lasers is explored.

Second, a total internal reflection-based coupled waveguide-resonator geometry, having applications to low power optical switching and modulation, is analyzed. This geometry makes use of the hybrid integration of a Mach-Zehnder interferometer with a racetrack resonator. Switching takes place using the Mach-Zehnder to control the coupling parameters in the vicinity of the critical coupling condition. Characterization of the static and dynamic output response of a thermooptically actuated InGaAsP-InP hybrid switch device demonstrates good ON-OFF switching contrast, microsecond response time, and reduced switching power in comparison with a conventional Mach-Zehnder configuration.

Finally, this work concludes by examining both the annular Bragg resonator and hybrid switch geometries in application to chemical and biological sensing. Both microcavity devices are shown to possess unique characteristics making them ideal for sensitive monitoring of small changes in the refractive index of a chemical or biological analyte.

Thesis Files