Two-photon superbunching effect of broadband chaotic stationary light at femtosecond timescale based on cascaded Michelson interferometer

TL;DR

This paper demonstrates a method to achieve and measure superbunching of broadband chaotic light using a cascaded Michelson interferometer, surpassing the traditional second-order coherence limit, with implications for enhanced weak signal detection.

Contribution

The paper introduces a novel experimental setup with a cascaded Michelson interferometer to observe superbunching of chaotic light exceeding the classical limit, supported by a developed theoretical model.

Findings

Degree of second-order coherence reached 2.42, exceeding the limit of 2.

Superbunching correlation peak width is about 95 fs.

Theoretical predictions match experimental results and suggest higher coherence with multiple circulations.

Abstract

It is challenging for observing superbunching effect with true chaotic light, here we propose and demonstrate a method to achieve superbunching effect of the degree of second-order coherence is 2.42 with broadband stationary chaotic light based on a cascaded Michelson interferometer (CMI), exceeding the theoretical upper limit of 2 for the two-photon bunching effect of chaotic light. The superbunching correlation peak is measured with an ultrafast two-photon absorption detector which the full width at half maximum reaches about 95 fs. Two-photon superbunching theory in a CMI is developed to interpret the effect and is in agreement with experimental results. The theory also predicts that the degree of second-order coherence can be much greater than $2$ if chaotic light propagates $N$ times in a CMI. Finally, a new type of weak signals detection setup which employs broadband chaotic light circulating in a CMI is proposed. Theoretically, it can increase the detection sensitivity of weak signals 79 times after the chaotic light circulating 100 times in the CMI.