Spatial, spectral and temporal coherence of ultra-intense twin beams

TL;DR

This paper investigates the coherence properties of ultra-intense twin beams generated through parametric interactions, revealing how coherence varies with pump power and identifying conditions for maximal coherence and additional coherence maxima.

Contribution

It introduces a model based on spatio-spectral Schmidt modes and generalized parametric approximation to analyze coherence in regimes with pump depletion, highlighting novel coherence behaviors.

Findings

Coherence increases with pump power at moderate levels but decreases when pump depletion occurs.

Maximal coherence conditions depend on pump-beam spectral width and transverse radius.

Additional coherence maxima are predicted at higher pump powers due to mode oscillations.

Abstract

Using the model of parametric interaction based on the spatio-spectral Schmidt modes and generalized parametric approximation, we analyze coherence and mode structure of ultra-intense twin beams generated in the regime with pump depletion. We show that the increase of spatial and spectral coherence with the increasing pump power observed for moderate powers is replaced by the decrease for the pump powers at which pump depletion occurs. This behavior of coherence is opposed to that exhibited by the number of spatio-spectral modes effectively constituting the twin beam. The conditions for maximal coherence are analyzed considering pump-beam parameters (spectral width, transverse radius). The existence of additional coherence maxima occurring at even higher pump powers is predicted and explained by the oscillatory evolution of the modes' populations.