A silicon source of heralded single photons at 2 $\hat{I}¼$m

Abstract

Mid infrared integrated quantum photonics is a promising platform for applications in sensing and metrology. However, there are only few examples of on-chip single photon sources at these wavelengths. These have limited performances with respect to their C-band counterparts. In this work, we demonstrate a new approach to generate heralded single photons in the mid infrared on a silicon chip. By using a standard C-band pump, the inter-modal spontaneous four wave mixing enables the generation of the herald idler at 1259.7 nm and the heralded signal at 2015 nm. The idler photon is easily detected with a common infrared single photon detector while the signal photon is upconverted to the visible before its detection. In this way, we are able to operate a mid infrared source without the need of mid infrared detectors and laser sources. By measuring a heralded $g^{(2)}$ of $0.23\pm 0.08$ we demonstrate the single photon behaviour of the source as well as the feasibility of multi-photon coincidence measurements beyond 2 $\hat{I}¼$m with our setup. The source exhibits a high intrinsic heralding efficiency of $(59\pm 5)\%$, a maximum coincidence to accidental ratio of $40.4\pm 0.9$ and a generation probability of $\left(0.72\pm 0.10\right)$ W${}^{-2}$.