Development of ultra-high-Q optical resonators with embedded diamond color centers

Abstract

Optical microresonators are small-scaled devices that can confine light at resonant frequencies within the structure. Whispering-gallery-mode optical microresonators are eloquently fabricated sub-class of optical microresonators offering high-quality factor and small mode. Typical whispering-gallery-mode microresonators include microdisks, microtoroids, microspheres, and microring resonators. Popular demand for a deterministic single-photon source made the defects in crystals heavily investigated. Some of the desired properties of these single-photon emitters are high-brightness, high purity in single-photon emission, narrow bandwidth, and single-photon emission at room temperature. Besides, depending on the application, additional properties might be sought such as high coherence time and degenerate spin energies. Thus, the crystals with high Debye temperature and large band-gap energy that can offer defects are in the focus of interest of the researchers. One promising candidate is diamond. Fortunately, diamond lattice can host several optically active defect sites. In this research, we only focus on Nitrogen-Vacancy color center in diamond due to being well researched and vendor availability. We investigate the methods to bring these two powerful elements of photonics together. We used nanodiamonds doped with Nitrogen-Vacancy color centers and microdisk and microtoroid resonators to investigate the methods to bring them together to obtain an emitter-cavity interface.In this work, we investigate and develop methods to embed a nanodiamond in the proximity of an optical mode of cavity made out of silica which readily offers high-Q factor by advanced nanofabrication techniques. Proposedly, melting and deformation of microdisk resonators under surface tension offer the possibility to a nanodiamond existing at the right position on the surface of microdisk to get included inside the cavity. Then we investigate methods and parameters of coating nanodiamond on microdisk in order to place them into the right positions.