Effect of dispersion on indistinguishability between single-photon wave-packets

TL;DR

This study explores how dispersion affects the indistinguishability of single-photon wave-packets using Hong-Ou-Mandel interference, revealing conditions for dispersion cancellation and methods to measure dispersion effects.

Contribution

It demonstrates how second-order dispersion influences single-photon interference and introduces a way to measure dispersion effects through HOM interference.

Findings

Dispersion cancellation occurs when both paths have equal dispersion.

Unbalanced dispersion broadens the interference curve.

The second-order dispersion coefficient can be measured via HOM interference.

Abstract

With propagating through a dispersive medium, the temporal-spectral profile of laser pulses should be inevitably modified. Although such dispersion effect has been well studied in classical optics, its effect on a single-photon wave-packet, i.e., the matter wave of a single-photon, has not yet been entirely revealed. In this paper, we investigate the effect of dispersion on indistinguishability of single-photon wave-packets through the Hong-Ou-Mandel (HOM) interference. By dispersively manipulating two indistinguishable single-photon wave-packets before interfering with each other, we observe that the difference of the second-order dispersion between two optical paths of the HOM interferometer can be mapped to the interference curve, indicating that (1) with the same amount of dispersion effect in both paths, the HOM interference curve must be only determined by the intrinsic indistinguishability between the wave-packets, i.e., dispersion cancellation due to the indistinguishability between Feynman paths; (2) unbalanced dispersion effect in two paths cannot be cancelled and will broaden the interference curve thus providing a way to measure the second-order dispersion coefficient. Our results suggest a more comprehensive understanding of the single-photon wave-packet and pave ways to explore further applications of the HOM interference.