Bright and pure single-photon source in a silicon chip by nanoscale positioning of a color center in a microcavity

Abstract

We present an all-silicon source of near-infrared linearly-polarized single photons, fabricated by nanoscale positioning of a color center in a silicon-on-insulator microcavity. The color center consists of a single W center, created at a well-defined position by Si${}^{+}$ ion implantation through a 150 nm-diameter nanohole in a mask. A circular Bragg grating cavity resonant with the W's zero-phonon line at 1217 nm is fabricated at the same location as the nanohole. By Purcell enhancement of zero-phonon emission, we obtain a photon count rate of $1.29\pm 0.01$ Mcounts/s at saturation under above-gap continuous-wave excitation with a Debye-Waller factor of $98.6\pm 1.4\%$. A clean photon antibunching behavior is observed up to pump powers ensuring saturation of the W's emission ($g^{(2)}(0)=0.06\pm 0.02$ at $P=9.2P_{sat}$), evidencing that the density of additional parasitic fluorescent defects is very low. We also demonstrate the triggered emission of single photons with $93\pm 2\%$ purity under weak pulsed laser excitation. At high pulsed laser power, we reveal a detrimental effect of repumping processes, that could be mitigated using selective pumping schemes in the future. These results represent a major step towards on-demand sources of indistinguishable near-infrared single photons within silicon photonics chips.