Schmidt-like coherent mode decomposition and spatial intensity correlations of thermal light

TL;DR

This paper experimentally demonstrates that the spatial intensity correlations of thermal light can be decomposed into a unique set of coherent modes, similar to Schmidt modes in entangled photons, using a mode selection technique.

Contribution

It extends the technique of spatial mode selection from quantum entanglement to classical thermal light, revealing a unique basis of coherent modes for intensity correlations.

Findings

Existence of a unique basis of coherent modes for thermal light

Extension of quantum mode selection techniques to classical light

Demonstration of spatial intensity correlations in thermal sources

Abstract

We experimentally study the properties of coherent mode decomposition for intensity correlation function of quasi-thermal light. We use the technique of spatial mode selection developed for studying transverse entanglement of photon pairs, and show that it can be extended to characterize classical spatial correlations. Our results demonstrate the existence of a unique for a given thermal source basis of coherent modes, correlated in a way much resembling the Schmidt modes of spatially entangled photons.