Recent progress in diamond photonics

We detail the passivation of ultra-high purity diamond and subsequent homoepitaxial growth of thin diamond layers containing spectrally stable nitrogen vacancy (NV) centres. We demonstrate a reduction of three orders of magnitude in the density of fluorescent NV centres in single crystal diamond due to hydrogen plasma treatment. This reduced fluorescence extends to a depth of 80 μm below the diamond surface and provides a clean slate upon which subsequent growth and characterisation of high quality isolated NV centres is possible. The photoluminescence excitation linewidth of NV centres in a 100 nm thick layer are measured to be as low as 140 MHz at T <; 12 K, with favourable spin properties. The combination of these two methods is an important step toward scalable and practical diamond based photonic devices suitable for quantum information processing.