Characterization of an asynchronous source of heralded single photons generated at a wavelength of 1550 nm

TL;DR

This paper thoroughly analyzes asynchronous heralded single photon sources at 1550 nm, highlighting their advantages over synchronous sources under certain conditions, and provides a detailed methodology for efficiency determination and performance evaluation.

Contribution

It introduces a comprehensive analysis framework for asynchronous single photon sources, including efficiency calculations and performance comparisons with synchronous sources.

Findings

Asynchronous sources outperform synchronous ones in multiphoton suppression when coupling efficiencies are near perfect.

The studied source achieves a 48% probability of delivering a heralded 1550 nm photon.

The photon statistics are highly sub-Poissonian, indicating low multiphoton probability.

Abstract

We make a thorough analysis of heralded single photon sources regarding how factors such as the detector gate-period, the photon rates, the fiber coupling efficiencies, and the system losses affect the performance of the source. In the course of this we give a detailed description of how to determine fiber coupling efficiencies from experimentally measurable quantities. We show that asynchronous sources perform, under most conditions, better than synchronous sources with respect to multiphoton events, but only for nearly perfect coupling efficiencies. We apply the theory to an asynchronous source of heralded single photons based on spontaneous parametric downconversion in a periodically poled, bulk, KTiOPO4 crystal. The source generates light with highly non-degenerate wavelengths of 810 nm and 1550 nm, where the 810 nm photons are used to announce the presence of the 1550 nm photons inside a single-mode optical fiber. For our setup we find the probability of having a 1550 nm photon present in the single-mode fiber, as announced by the 810 nm photon, to be 48%. The probability of multiphoton events is strongly suppressed compared to a Poissonian light source, giving highly sub-Poisson photon statistics.