Bright source of spectrally uncorrelated polarization-entangled photons with nearly single-mode emission

TL;DR

This paper reports a bright, nearly single-mode polarization-entangled photon source at 1552 nm with high pair generation rate and minimal spectral/spatial entanglement, suitable for quantum communication.

Contribution

The authors demonstrate a high-brightness, spectrally uncorrelated polarization-entangled photon source using group velocity matching and innovative beam overlap techniques.

Findings

Pair generation rate of 123,000 pairs/s/mW.

Polarization-entanglement visibility of 94.7%.

Minimal spectral and spatial entanglement achieved.

Abstract

We present results of a bright polarization-entangled photon source operating at 1552 nm via type-II collinear degenerate spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We report a conservative inferred pair generation rate of 123,000 pairs/s/mW into collection modes. Minimization of spectral and spatial entanglement was achieved by group velocity matching the pump, signal and idler modes and through properly focusing the pump beam. By utilizing a pair of calcite beam displacers, we are able to overlap photons from adjacent down-conversion processes to obtain polarization-entanglement visibility of 94.7 +/- 1.1% with accidentals subtracted.