An efficient integrated two-color source for heralded single photons

Abstract

We present a pulsed and integrated, highly non-degenerate parametric down-conversion (PDC) source of heralded single photons at telecom wavelengths, paired with heralding photons around 800 nm. The active PDC section is combined with a passive, integrated wavelength division demultiplexer on-chip, which allows for the spatial separation of signal and idler photons with efficiencies of more than 96.5%, as well as with multi-band reflection and anti-reflection coatings which facilitate low incoupling losses and a pump suppression at the output of the device of more than 99%. Our device is capable of preparing single photons with efficiencies of 60% with a coincidences-to-accidentals ratio exceeding 7400. Likewise, it shows practically no significant background noise compared to continuous wave realizations. For low pump powers, we measure a conditioned second-order correlation function of g ^(2) = 3.8 × 10 ^−3 , which proves almost pure single-photon generation. In addition, our source can feature a high brightness of 〈 n _pulse 〉 = 0.24 generated photon pairs per pump pulse at pump power levels below 100 μ W. The high quality of the pulsed PDC process in conjunction with the integration of highly efficient passive elements makes our device a promising candidate for future quantum networking applications, where an efficient miniaturization plays a crucial role.