Distinguishing thermal and pseudothermal light by testing the Siegert relation

TL;DR

This paper introduces a method to test the Siegert relation to distinguish genuine thermal light from pseudothermal sources, addressing the challenge of verifying thermal properties in different light sources.

Contribution

The authors develop a direct testing technique for the Siegert relation applied to various photon-bunched light sources, enhancing the ability to identify true thermal light.

Findings

Successfully tested the Siegert relation for laser light scattered from rotating ground glass.

Verified the Siegert relation for spontaneously emitted light from a gas discharge lamp.

Demonstrated a fundamental criterion for identifying thermal light sources.

Abstract

Thermal light, including blackbody radiation and spontaneous emission, exhibits photon bunching. Thermal light sources, however, typically yield low spectral densities, limiting their practical utility. Pseudothermal light sources with higher brightness and longer coherence time are often employed instead. While pseudothermal light also exhibits photon bunching, this property may not suffice to fully replicate the behavior of genuine thermal light. Here we demonstrate a method to directly test the Siegert relation for two sources of photon-bunched light, laser light scattered from a rotating ground glass and spontaneously emitted light from a gas discharge lamp, probing a fundamental criterion expected of thermal light.