Bandwidth control of the biphoton wavefunction exploiting spatio-temporal correlations

TL;DR

This paper investigates how the spatial properties of detection and pump beams influence the spectral bandwidth of biphotons generated via spontaneous parametric down conversion, enabling simple experimental bandwidth control through optical configuration adjustments.

Contribution

It demonstrates that the spectral bandwidth of biphotons can be effectively controlled by detection beam waists, and provides a phase and temporal shape characterization using Hong-Ou-Mandel interferometry.

Findings

Bandwidth is mainly affected by detection beam waist.

Experimental control of biphoton spectrum is achievable by optical configuration.

Toy model accurately explains experimental observations.

Abstract

In this work we study the spatio-temporal correlations of photons produced by spontaneous parametric down conversion. In particular, we study how the waists of the detection and pump beams impact on the spectral bandwidth of the photons. Our results indicate that this parameter is greatly affected by the spatial properties of the detection beam, while not as much by the pump beam. This allows for a simple experimental implementation to control the bandwidth of the biphoton spectra, which only entails modifying the optical configuration to collect the photons. Moreover, we have performed Hong-Ou-Mandel interferometry measurements that also provide the phase of the biphoton wavefunction, and thereby its temporal shape. We explain all these results with a toy model derived under certain approximations, which accurately recovers most of the interesting experimental details.