Control of Optical Processes in Diamond using Plasmonic Nanogap Cavities

Solid-state quantum emitters embedded in carefully engineered nanostructures could enable a new generation of quantum information and sensing technologies, including networked processors for quantum computing and precise monitors of temperature and strain at the nanoscale. The primary goal when designing these nanostructures is to utilize the Purcell effect to improve the emission rate, directionality and brightness of quantum emitters, as long decay times, nondirectional emission and weak fluorescence limit their applications. One particularly promising emitter is the silicon vacancy (SiV) in diamond, which offers excellent photostability and minimal spectral diffusion, in addition to coherent emission at its zero-phonon line (ZPL) comprising 80% of its total fluorescence. In this dissertation, up to 121-fold enhancement of the spontaneous emission rate of SiVs coupled to plasmonic nanogap cavities is demonstrated. The vacancy centers are implanted into a monolithic diamond thin film, which is then etched to nanometer-scale thickness, an approach with a clear path towards wafer-scale fabrication. A novel approach to creating film-coupled nanogap metasurfaces was developed to support this research and consists of transferring EBL-fabricated nanoparticles by using a PDMS stamp. Up to seven orders of magnitude of enhancement of nonlinear frequency conversion was also observed in diamond thin films coupled to these metasurfaces. Furthermore, a robust mechanism for actively tuning the nanocavity absorption resonance by integrating sub-10-nm films of the phase-change material vanadium dioxide. This platform opens up opportunities for on-chip quantum networks and nanoscale sensors based on nanocavity-coupled SiVs with the potential for in-situ frequency conversion to outcouple to photonic circuits and reconfigurable properties by incorporating VO2 thin films.