Building blocks for cavity quantum electrodynamics in on-chip buckled dome microcavities
Creators: Al-Sumaidae, Sanaa Numan Mohammed
Publisher: name: University of Alberta Library
Year: 2022

<p>Technologies for controlling spontaneous emission have attracted considerable attention over the past few decades, and have most recently been concerned with the realization of several quantum light sources such as the threshold-less laser and the controlled source of single photons. The emission rate and directivity of an atomic emitter can be modified through the appropriate design of the surrounding electromagnetic environment. Optical microcavities play a central role in efforts to modify the spontaneous emission rate. The interaction between a cavity mode and an emitter can lead to an enhanced rate of emission into a desired mode and/or a suppressed /inhibited rate of emission into undesired modes.<br>
This research is mainly a theoretical and experimental study of the control/modification of the spontaneous emission rates for dipole emitters embedded inside ‘half-symmetric’ curved-mirror Fabry Perot cavities with omnidirectional mirror claddings.  These cavities are fabricated using a monolithic ‘buckling’ self-assembly process. In theoretical work, we demonstrated that omnidirectional Bragg reflectors can enable significant inhibition of background emission, and thus might greatly enhance the single-atom cooperativity and the spontaneous emission coupling factor into a desired mode of such cavities. In experimental work, we explored monolithic strategies to embed various emitters, including erbium-doped thin films, inside these cavities.  Preliminary evidence for cavity-enhanced emission was achieved, although further optimization of these fabrication strategies is left for future work.<br>
The upper mirror in buckled dome microcavities is essentially a flexible membrane, offering unique options for tuning the resonance spectra. Resonance tuning is a pre-requisite for many cavity quantum electrodynamics (CQED) applications, such as those mentioned above. From another perspective, the shift in cavity resonance in response to changes in ambient pressure and temperature can be viewed as a modality for optical sensing.  The feasibility of utilizing such cavities as optical pressure sensors was investigated experimentally and theoretically, for two different sizes of buckled dome cavities with a-Si/SiO2-based mirrors.  These studies showed the potential for high sensitivity (&lt; 10 Pa), and good linearity over a pressure range &gt; 100 kPa for domes of 100 and 50 µm base diameters. We also measured the mechanical resonance frequencies for those domes, confirming theoretical predictions that the fundamental resonance frequencies lie in the MHz range.  With potential for high-speed response and on-chip fabrication in large arrays, buckled dome microcavities might be an interesting candidate for dynamic pressure sensing applications such as photo-acoustic imaging.  On the other hand, this study also suggests that rapid tuning of the optical resonance might be possible through control of the external pressure, a property which might be useful for some CQED applications such as the single-photon sources mentioned above.</p>