Coherence and dimensionality of intense spatio-spectral twin beams

TL;DR

This paper investigates how the coherence and entanglement dimensionality of intense spatio-spectral twin beams evolve with pump intensity, revealing that coherence increases in spectral, temporal, and wave-vector domains, but remains constant in the output plane.

Contribution

It provides a detailed analysis of the coherence properties and entanglement dimensionality of twin beams across different intensity regimes using mode decomposition and correlation functions.

Findings

Coherence increases with pump intensity in spectral, temporal, and wave-vector domains.

Coherence in the crystal output plane remains nearly constant regardless of pump intensity.

Entanglement dimensionality is evaluated using multiple approaches.

Abstract

Spatio-spectral properties of twin beams at their transition from low to high intensities are analyzed in parametric and paraxial approximations using the decomposition into paired spatial and spectral modes. Intensity auto- and cross-correlation functions are determined and compared in the spectral and temporal domains as well as the transverse wave-vector and crystal output planes. Whereas the spectral, temporal and transverse wave-vector coherence increases with the increasing pump intensity, coherence in the crystal output plane is practically independent on the pump intensity owing to the mode structure in this plane. The corresponding auto- and cross-correlation functions approach each other for larger pump intensities. Entanglement dimensionality of a twin beam is determined comparing several approaches.