KIT-led team reports 96% extinction contrast with tin-vacancy centers in diamond microcavity
Researchers at the Karlsruhe Institute of Technology, with the University of Stuttgart, Ulm University and the Fraunhofer Institute, coupled tin-vacancy (SnV) centers in diamond to a tunable Fabry-Pérot microcavity at temperatures down to 1 K. They report 96% extinction contrast, a Purcell factor of 4.1(1) in a diamond-like mode versus 1.85(5) in an air-like mode, and a coherent cooperativity of C = 4.0(14). The cavity used diamond membranes with 0.2 nanometer root mean square roughness, and an applied magnetic field split the extinction into two spin-selective branches with a contrast of 0.91. The authors say the SnV linewidth was twice the theoretical minimum because of charge-noise-induced spectral diffusion, and extrapolate to a cooperativity of 8.0(5) and contrast of 0.99(1) under ideal conditions.