Spatiotemporal entanglement in a noncollinear optical parametric amplifier

TL;DR

This paper theoretically analyzes the generation of entangled light beams in a noncollinear optical parametric amplifier, revealing spatio-temporal coupling effects and providing analytical and numerical solutions for the eigenmodes.

Contribution

It introduces an efficient Gaussian-based analytical method to determine spatio-temporal squeezing eigenmodes in noncollinear parametric downconversion.

Findings

Identified spatio-temporal coupling in the generated entangled beams.

Developed an analytical Gaussian model matching numerical results.

Showed that shorter pump pulses increase spatio-temporal coupling.

Abstract

We theoretically investigate the generation of two entangled beams of light in the process of single-pass type-I noncollinear frequency degenerate parametric downconversion with an ultrashort pulsed pump. We find the spatio-temporal squeezing eigenmodes and the corresponding squeezing eigenvalues of the generated field both numerically and analytically. The analytical solution is obtained by modeling the joint spectral amplitude of the field by a Gaussian function in curvilinear coordinates. We show that this method is highly efficient and is in a good agreement with the numerical solution. We also reveal that when the total bandwidth of the generated beams is sufficiently high, the modal functions cannot be factored into a spatial and a temporal parts, but exhibit a spatio-temporal coupling, whose strength can be increased by shortening the pump.