Organic dye molecules are excellent sources of indistinguishable photons and thus possess
great promise for various photonic quantum technologies such as quantum computing
and sensing. Our system of choice is a dibenzoterrylene (DBT) molecule in an anthracene (Ac) crystal. The molecular sources are limited, however, by a low collection efficiency (<1%) resulting in a reduction of single-photon source efficiency. That can be drastically improved through the use of optical cavities in order to collect all the photons into a single mode and accelerate the zero-phonon line radiative decay.
Integrated cavities are inherently stable since they are solid-state. Placing single molecules at the correct position within a cavity significantly alters the electric field around the quantum emitter. It suppresses the unwanted emission modes and enhances the one that we choose. The emitter then preferentially emits photons into a single spatial, spectral and polarisation mode, considerably increasing its efficiency.
In this thesis, I investigate various photonic structures proposed in our group or by our collaborators, each in a different stage of design, fabrication or testing. Circular Bragg gratings offer an exceptional emission redirection for collection to an objective lens,
while silicon nitride nanobeam cavities and disk resonators provide a route to photon sources integrated on photonic chips. Circular Bragg grating cavities are explored in detail, including FDTD simulations of several designs with varying device materials.
I also present a deterministic approach to fabricating these cavities around pre-chosen
molecules that is in the final stages of development. The nanobeam cavities are optically characterised and a scheme to incorporate molecules by a hole-filling method assisted by convective-capillary forces is outlined. Disk resonators are investigated in the confocal microscope regarding both their optical properties and coupling to DBT molecules. Further work and improvements for all designs are suggested. Additionally, a vertical cavity with a Gaussian defect is proposed as a way to localise the cavity mode into an easily accessible reservoir that can be filled with molecular sources.