Fluorescence lifetimes and refractometric sensing with cavity-coupled silicon quantum dots

• Author / Creator

  Chung, Deborah K

• This thesis explores the dynamics and sensing performance of silicon quantum dot (SiQD) ensembles coupled to the whispering gallery modes (WGMs) of spherical and cylindrical microcavities. The first project investigated the possibility of observing Purcell effects in an ensemble of QDs coupled to a microsphere resonator. However, no convincing evidence for rate modifications was found. Several possible reasons for this negative result were outlined and future experimental improvements were suggested. Next, the SiQDs were coupled to the WGMs of cylindrical cavities (fibers and microcapillaries) in order to investigate and optimize their refractive-index sensing performance. These sensors register a WGM wavelength shift in response to changes in local index of refraction. Using an SiQD coated optical fiber, the detection limit of the sensor was improved by projecting the WGM spectrum onto a full 2 dimensional CCD array. However, noise from various experimental sources limited the detection limit of the fiber sensor to a value of 2.4E-3 RIU. In order to further improve the ultimate limit of detection, a more mechanically stable device was constructed. This consisted of a microcapillary whose channel was coated with a layer of SiQDs embedded in a protective oxide matrix. By controlling the SiQD channel film thickness via an etching procedure, the device sensitivity to refractometric changes was maximized. Using the techniques developed to minimize the wavelength shift resolution, a detection limit of 1.7E-4 RIU was experimentally measured, which is less than a factor 2 larger than the calculated optimum theoretical limit of detection. This represents one of the best experimentally-observed detection limits reported for fluorescent WGM devices.

• Subjects / Keywords

  • Microcavity
  • Microcapillary
  • Fluorescence
  • Purcell effect
  • Quantum dots
  • Optical fiber
  • Detection limit
  • Silicon
  • Microsphere
  • Sensitivity
  • Photoluminescence
  • Whispering gallery modes
  • Microresonator

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3J960Q9Z

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.