Noise reduction in 3D noncollinear parametric amplifier

TL;DR

This paper analytically derives an approximate Bloch-Messiah reduction for a noncollinear parametric amplifier, enabling optimization of signal gain and noise reduction through mode management and pump adjustments.

Contribution

It introduces a perturbative analytical approach to optimize mode structure and noise performance in noncollinear parametric amplifiers.

Findings

Fundamental mode is an elliptic Gaussian shape.

Higher order modes are approximately Hermite-Gaussian beams.

Pump waist adjustment can minimize noise in higher order modes.

Abstract

We analytically find an approximate Bloch-Messiah reduction of a noncollinear parametric amplifier pumped with a focused monochromatic beam. We consider type I phase matching. The results are obtained using a perturbative expansion and scaled to a high gain regime. They allow a straightforward maximization of the signal gain and minimization of the parametric fluorescence noise. We find the fundamental mode of the amplifier, which is an elliptic Gaussian defining the optimal seed beam shape. We conclude that the output of the amplifier should be stripped of higher order modes, which are approximately Hermite-Gaussian beams. Alternatively, the pump waist can be adjusted such that the amount of noise produced in the higher order modes is minimized.