Spatial control of entangled two-photon absorption with organic chromophores.

Entangled photons generated by spontaneous parametric down-conversion (SPDC) have been used to investigate entangled two-photon absorption (ETPA) in multiannulene systems. The ETPA characteristics are shown to depend on the spatial orientation of the SPDC emission pattern. The expected dependence of the absorption rate on input flux is seen for emission patterns that exhibit spatial indistinguishability between the signal and idler photons, while no absorption is observed for a spatially distinguishable emission pattern. The amount of absorption of entangled photons is also seen to depend on the degree of overlap of the entangled photons for the indistinguishable conditions. Tunability of the entangled photon absorption can thus be achieved by utilizing the spatial characteristics of the entangled photon pairs.