Measuring the second order correlation function and the coherence time using random phase modulation

TL;DR

This paper introduces a novel method to measure the second order correlation function and coherence time of light sources using random phase modulation, offering improved accuracy for weak sources with long coherence times.

Contribution

The paper presents a new technique for measuring $g^{(2)}$ and coherence time that is more effective for weak light sources compared to traditional methods.

Findings

High order correction improves $g^{(2)}$ accuracy when $ar{I} au_{c}$ is significant.

The method accurately measures coherence time using random phase modulation.

Compared to self-heterodyne detection, the new approach is better for weak, long-coherence light sources.

Abstract

A new approach to measure the second order correlation function $g^{(2)}$ and the coherence time was investigated. The $g^{(2)}$ was calculated from the photon pair time interval distribution by direct numerical self-convolution with the high order correction. The accuracy of this method was examined using an optical fiber based Hanbury-Brown-Twiss interferometer with a pseudo-thermal light source. We found that the significance of the high order correction is related to the factor $\bar{I}\tau_{c}$, which is the overlapping of the photon wave packets. A novel technique was also demonstrated to measure the coherence time $\tau_c$ of a light source using the random phase modulation. In comparison with the conventional self-heterodyne detection, this method is more suitable for a weak light source with a long coherence time.