Excitation with entangled photon pairs may lead to an increase in the efficiency of two-photon absorption at low photon flux. The corresponding process, entangled two-photon absorption (E2PA), has been investigated in numerous theoretical and experimental studies. However, significant ambiguity and inconsistency remain in the literature about the absolute values of E2PA cross-sections. Here, we use a fluorescence-based registration scheme to experimentally determine upper bounds on the cross-sections for six fluorophores. These bounds are up to four orders of magnitude lower than the smallest published cross-section. For two samples that have been studied by others, Rhodamine 6G and 9R-S, we measure upper bounds four and five orders of magnitude lower than the previously reported cross-sections.
@article{arxiv.2008.02664,
title = {Setting bounds on two-photon absorption cross-sections in common fluorophores with entangled photon pair excitation},
author = {Kristen M. Parzuchowski and Alexander Mikhaylov and Michael D. Mazurek and Ryan N. Wilson and Daniel J. Lum and Thomas Gerrits and Charles H. Camp and Martin J. Stevens and Ralph Jimenez},
journal= {arXiv preprint arXiv:2008.02664},
year = {2021}
}