Multi-photon and quantum communication experiments such as loophole-free Bell tests and device independent quantum key distribution require entangled photon sources which display high coupling efficiency. In this paper we put forward a simple quantum theoretical model which allows the experimenter to design a source with high pair coupling efficiency. In particular we apply this approach to a situation where high coupling has not been previously obtained: we demonstrate a symmetric coupling efficiency of more than 80% in a highly frequency non-degenerate configuration. Furthermore, we demonstrate this technique in a broad range of configurations, i.e. in continuous wave and pulsed pump regimes, and for different nonlinear crystals.
@article{arxiv.1309.2457,
title = {High efficiency coupling of photon pairs in practice},
author = {T. Guerreiro and A. Martin and B. Sanguinetti and N. Bruno and H. Zbinden and R. T. Thew},
journal= {arXiv preprint arXiv:1309.2457},
year = {2014}
}