Spatial properties of entangled two-photon absorption

TL;DR

This study investigates how the spatial properties of entangled photon pairs influence two-photon absorption in Rhodamine 6G, revealing dependence on flux attenuation type and beam waist size, with implications for understanding dye cross-sections.

Contribution

It provides experimental insights into the spatial dependence of entangled two-photon absorption, comparing it to classical processes, and clarifies the variability in reported cross-sections.

Findings

Entangled two-photon absorption rate depends linearly on flux attenuation.

Beam waist size affects entangled two-photon absorption similarly to classical two-photon absorption.

Results suggest variability in reported entangled two-photon absorption cross-sections.

Abstract

We experimentally study entangled two-photon absorption in Rhodamine 6G as a function of the spatial properties of a high flux of broadband entangled photon pairs. We first demonstrate a key signature dependence of the entangled two-photon absorption rate on the type of entangled pair flux attenuation: linear, when the laser pump power is attenuated, and quadratic, when the pair flux itself experiences linear loss. We then perform a fluorescence-based Z-scan measurement to study the influence of beam waist size on the entangled two-photon absorption process and compare this to classical single- and two-photon absorption processes. We demonstrate that the entangled two-photon absorption shares a beam waist dependence similar to that of classical two-photon absorption. This result presents an additional argument for the wide range of contrasting values of quoted entangled two-photon absorption cross-sections of dyes in literature.