Photophysics of Germanium-Vacancy centers in Diamond

Point defects in diamond are promising candidates in the solid-state for a wide range of applications in quantum information processing. Among different defects with allowed optical transitions, the germanium-vacancy center (GeV) is attractive because it has good optical properties at room temperature, including a narrow zero-phonon line and low emission into the phonon sideband. Some of the GeV center's intrinsic physical properties are yet unknown. This contribution focuses on the optical investigation of single GeV center deeply implanted into a synthetic diamond crystal at a cryogenic sample temperature of 4K. Single GeV center's optical properties are monitored by collecting photons emitted in the phonon side band and the zero-phonon line using a cross-polarization scheme. Applying a resonant optical excitation scheme, we report on the observation of fluorescence switching effects with the evidence of a dark shelving state, optical gating of the phonon-sidebands emission with the addition of weak power off-resonant laser, and discrete spectral jumps. Further, evidence of nonclassical states of light is studied using a dual correlation approach. Finally, a fiber-based Fabry-Pérot microcavity in a bath cryostat design is proposed as a low vibration solution for enabling Purcell enhancement.