Efficient and spectrally bright source of polarization-entangled photons

Abstract

We demonstrate an efficient fiber-coupled source of nondegenerate polarization-entangled photons at 795 and $1609\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ using bidirectionally pumped parametric down-conversion in bulk periodically poled lithium niobate. The single-mode source has an inferred bandwidth of $50\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ and a spectral brightness of $300\phantom{\rule{0.3em}{0ex}}\text{pairs}∕(\mathrm{s}\phantom{\rule{0.2em}{0ex}}\mathrm{GHz}\phantom{\rule{0.2em}{0ex}}\mathrm{mW})$ of pump power that is suitable for narrowband applications such as entanglement transfer from photonic to atomic qubits.