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Updated: May 13, 2026

Measuring Diffusion Coefficients via Two-photon Fluorescence Recovery After Photobleaching
Published on: February 26, 2010
Measurement of the Entangled Two-Photon Absorption Cross-Sections of 4-Aminoazobenzene
Sena Hashimoto1,2, Hisaki Oka1, Izumi Iwakura1
1Kanagawa University, Yokohama, Japan.
Abstract:
Recently, entangled two-photon absorption (ETPA) has attracted considerable attention, yet reported cross-sections vary widely. In this study, we focused on 4-aminoazobenzene, an azobenzene derivative that exhibits extremely low one-photon absorption in the wavelength range of time-entangled photon pairs. By measuring the time correlation between the two photons transmitted through the sample solution and separating correlated from uncorrelated counts, we distinguished between ETPA and linear-loss contributions. The ETPA cross-section is only ≈107-fold lower than the one-photon absorption cross-section and ≈1018-fold higher than the classical TPA cross-section (evaluated under classical two-photon excitation at a photon-flux density of ≈108 photons·s-1·cm-2). Moreover, ETPA is measurable at a photon-flux density of ≈108 photons·s-1·cm-2.
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