Photon Collection Enhancement of Shallow Single Spin Defects in Silicon Carbide

Recent studies have widely acknowledged the utility of silicon carbide (SiC) spin defects in solid-state quantum information processing. However, the practical implementation of these spin defects encounters challenges arising from the high refractive index of SiC, resulting in a significant decrease in the collected efficiency of the color center fluorescence. In this work, we greatly enhance the collection efficiency of these shallow color centers by utilizing plasmonic enhancement and solid immersion lenses on SiC films. We have successfully elevated the saturated fluorescence counts to over 1 Mcps (mega counts per second) of single divacancy spin defects while preserving their spin properties, which is ten times higher than the bulk sample. Notably, our methodology showcases a notable reduction (approximately one-fourth) in background fluorescence under identical excitation laser conditions. Consequently, our research successfully improves the collection efficiency of broad-spectrum spin signals and contributes to advancements in quantum sensing sensitivity by harnessing shallow spin defects. The findings from our investigation hold significant implications beyond the scope of SiC spin defects as the outlined approach exhibits potential for improving the photon collection efficiency of other solid-state spin defects.