Imaging and quantum-efficiency measurement of chromium emitters in diamond

We present direct imaging of the emission pattern of individual chromium-based single photon emitters in diamond and measure their quantum efficiency. By imaging the excited state transition dipole intensity distribution in the back focal plane of high numerical aperture objective, we determined its 3D orientation. Employing ion implantation techniques, the emitters were placed at various distances from the diamond-air interface. By comparing the decay rates from the single chromium emitters at different depths in the diamond crystal, we measured an average quantum efficiency of 28%.