Experimental upper bounds for resonance-enhanced entangled two-photon absorption cross section of indocyanine green.
J Chem Phys
; 160(9)2024 Mar 07.
Article
en En
| MEDLINE
| ID: mdl-38445732
ABSTRACT
Resonant intermediate states have been proposed to increase the efficiency of entangled two-photon absorption (ETPA). Although resonance-enhanced ETPA (r-ETPA) has been demonstrated in atomic systems using bright squeezed vacuum, it has not been studied in organic molecules. We investigate for the first time r-ETPA in an organic molecular dye, indocyanine green (ICG), when excited by broadband entangled photons in near-IR. Similar to many reported virtual state mediated ETPA (v-ETPA) measurements, no r-ETPA signals are measured, with an experimental upper bound for the cross section placed at 6(±2) × 10-23 cm2. In addition, the classical resonance-enhanced two-photon absorption (r-TPA) cross section of ICG at 800 nm is measured for the first time to be 20(±13) GM, where 1 GM equals 10-50 cm4 s, suggesting that having a resonant intermediate state does not significantly enhance two-photon processes in ICG. The spectrotemporally resolved emission signatures of ICG excited by entangled photons are also presented to support this conclusion.
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Colección:
01-internacional
Banco de datos:
MEDLINE
Idioma:
En
Revista:
J Chem Phys
Año:
2024
Tipo del documento:
Article
País de afiliación:
Estados Unidos