Photon Collection Enhancement of Shallow Single Spin\nDefects in Silicon Carbide

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