Experimental investigation of the effect of dispersion on squeezing generation in a synchronously pumped optical parametric oscillator

TL;DR

This study experimentally examines how intracavity dispersion affects squeezing in a SPOPO, revealing that squeezing levels are unaffected by dispersion variations, contrary to theoretical expectations.

Contribution

It introduces a new modeling approach that treats intracavity dispersion as an effective spectral filter within the SPOPO's interaction Hamiltonian.

Findings

Squeezing levels remain unchanged despite dispersion variations.

A spectral filtering model explains the experimental results.

Highlights the importance of spectral filtering in multimode squeezing.

Abstract

An experimental investigation of intracavity dispersion effects in a synchronously pumped optical parametric oscillator (SPOPO) is presented. A flexible setup combining spectral and phase shaping of both pump and local oscillator fields with frequency-resolved balanced homodyne detection is employed to examine how intracavity dispersion influences squeezing. Different cavity configurations with varying finesse and dispersion conditions are studied, and the squeezing is measured as a function of pump power and local oscillator bandwidth. Contrary to expectations based on existing theoretical models, the measured squeezing levels remain essentially unchanged as dispersion varies. To account for these observations, a modeling approach is introduced in which intracavity dispersion is described as an effective spectral filtering occurring at the stage of SPOPO supermode generation. Within this framework, the filtering is incorporated directly into the interaction Hamiltonian of the nonlinear process. This perspective establishes a consistent experimental benchmark for the study of dispersion in SPOPOs and underscores the importance of spectral filtering in the interpretation of multimode squeezing experiments.