Closed-Loop Spectroscopy and Nanofabrication Around Individual Quantum Emitters

Diamond color centers, with a particular focus on nitrogen vacancy (NV) and tin-vacancy (SnV), have assumed pivotal roles in the realm of quantum information technology. These color centers function as interfaces for photons to interact with electron and nuclear spin ground states, propelling explorations into diverse quantum applications, including quantum networks, quantum computing, and quantum sensing. Yet, a substantial hurdle within this domain pertains to the fabrication of photonic nanostructures like waveguides and photonic crystal nanocavities, which are essential for the efficient control and interaction of photons with color center spins. To tackle these challenges, we introduce a novel approach that combines in-situ maskless etching with high-resolution hyperspectral cathodoluminescence (CL) measurements conducted concurrently. Specifically, we harness electron beam-induced surface chemistry to etch through diamond precisely at the color center's location, all the while capturing emission properties. Our work has successfully achieved remarkable fabrication precision, achieving resolutions as fine as 20 nm creating predefined patterns, and enabling the production of perforations in suspended waveguides. Furthermore, we continuously monitor color center intensity throughout the etching process in terms of both time and depth using cathodoluminescence and free-space laser techniques. Our findings underscore the spatial precision needed to pattern diamond structures, shaping cavities or exposing quantum emitters, while simultaneously tracking optical properties like peak position and brightness enhancement.