Pulsed squeezed light: Simultaneous squeezing of multiple modes

TLDR

The study analyzes the spectral properties of squeezed light generated by pulsed, single‑pass degenerate parametric down‑conversion. The authors decompose the multimode output into independent squeezing modes using a Schmidt‑like decomposition, develop a simple analytical model in the perturbative regime, and perform numerical simulations for strong pumping in a beta‑barium‑borate waveguide. Characterizing the squeezing modes reveals that efficient homodyne detection is possible over a broad range of local‑oscillator modes in weak pumping, but in the intense regime stringent mode matching is required, otherwise detected squeezing can decrease with higher pump power due to identified inefficiencies.

Abstract

We analyze the spectral properties of squeezed light produced by means of pulsed, single-pass degenerate parametric down-conversion. The multimode output of this process can be decomposed into characteristic modes undergoing independent squeezing evolution akin to the Schmidt decomposition of the biphoton spectrum. The main features of this decomposition can be understood using a simple analytical model developed in the perturbative regime. In the strong pumping regime, for which the perturbative approach is not valid, we present a numerical analysis, specializing to the case of one-dimensional propagation in a beta-barium borate waveguide. Characterization of the squeezing modes provides us with an insight necessary for optimizing homodyne detection of squeezing. For a weak parametric process, efficient squeezing is found in a broad range of local oscillator modes, whereas the intense generation regime places much more stringent conditions on the local oscillator. We point out that without meeting these conditions, the detected squeezing can actually diminish with the increasing pumping strength, and we expose physical reasons behind this inefficiency.