Controlling the transverse correlation in QPM parametric down-conversion

TL;DR

This paper investigates how the transverse spatial correlation of photon pairs generated via spontaneous parametric down-conversion in periodically poled crystals can be controlled by modulating the pump beam's spatial shape, both theoretically and experimentally.

Contribution

It introduces a novel technique for controlling biphoton transverse correlation in QPM gratings through pump beam shape modulation, supported by theoretical and experimental evidence.

Findings

Pump beam shape modulation controls biphoton transverse correlation.

The technique is effective in nearly collinear geometries.

Experimental results confirm theoretical predictions.

Abstract

In this work we study the transverse spatial correlation of the pair of photons generated via the process of spontaneous parametric frequency down-conversion, in periodically poled non-linear crystals illuminated by a pulsed laser beam. It is well known that the two-photon state generated in quasi-phase matching (QPM) configurations depends explicitly on the characteristics of the pump beam, on the crystal modulated non-linearity, and on the detection geometry. This has allowed the development of several techniques for controlling the biphoton spectral and spatial properties. Here we discuss another technique for implementing the spatial entanglement modification in QPM gratings. We show, theoretically and experimentally, that in nearly collinear geometries, the spatial shape modulation of the pump beam allows for the control of the biphoton transverse spatial correlation.