A room temperature single photon source, cavity coupling of single solid-state defects to open-access microcavitie

Thesis

Room temperature solid-state emitters provide a promising source of single photons for use in quantum technologies. The emitters studied in this thesis are the nitrogen-vacancy (NV) centre in diamond, and defects in two-dimensional hexagonal boron nitride (hBN). In this thesis, I present investigations into the coupling of these defects to open-access microcavities at room temperature. The optical microcavity serves to confine the electric field down to mode volumes on the order of λ³, increasing the spontaneous emission rate of these emitters and channelling this emission into well defined cavity modes. The general properties of both emitters will be presented, including examples of single photon emission, emission spectra, saturation behaviour and photo-stability. A few examples highlighting the long-term photo-stability of the NV centre under pulsed excitation will be displayed. This will highlight the suitability of the NV centre for a practical device. Following the preparation and characterisation of each emitter, single photon emission into the cavity modes is verified, reaching single photon purities greater than 97%. Enhancements in the spectral density of photons were observed for both the NV centre (~25×) and defect in hBN (~3×), along with decreases in the excited state lifetimes. While the NV centre provides a stable source of single photons, the cavity enhancement is limited by its broad emission spectrum. Defects in hBN present near-ideal optical properties in the absence of the cavity, and were expected to deliver superior results within the cavity. However, the poor photo-stability of these defects did not allow complete characterisation of the cavity coupled emission. FDTD simulations were combined with changes in the excited state lifetime to infer the quantum efficiency of these defects. The results of this thesis form the foundation for the realisation of a robust room temperature single photon source.

Authors: Adekanye, S

• DOI: 10.5287/ora-e20x40rbv
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Microcavities; Nitrogen-vacancy centre; Single Photon Emission; Nanodiamonds
• Subjects: Nanodiamonds; Nitrogen-vacancy centre; Hexagonal Boron Nitride; Single Photon Source; Optical Microcavities; Quantum Technologies; Single Photon Emission; Solid-state defects; Quantum Optics