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Predictability of non-degenerate two-photon absorption spectra (Conference Presentation)
Author(s): Sanaz Sadegh; Mu-Han Yang; Christopher G. L. Ferri; Martin Thunemann; Payam A. Saisan; Anna Devor; Yeshaiahu Fainman

Paper Abstract

In non-degenerate two-photon excitation (ND-TPE), electronic transition of fluorophores happens via absorption of two photons with different energies. This contrasts with conventional - or degenerate - two-photon excitation (D-TPE), where two photons with identical energies are absorbed. ND-TPE can improve performance of two-photon microscopy by extending the excitation wavelength range, reducing out-of-focus excitation, and increasing resolution and penetration depth. However, a systematic study of fluorophore performance under ND-TPE is missing, which is critical for the selection of optimal excitation wavelength combinations. It is a well-known fact that degenerate two-photon absorption spectra often deviate from theoretical predictions based on one-photon absorption spectra. Therefore, it is not clear whether non-degenerate two-photon absorption spectra are predictable from the corresponding degenerate spectra. Using our sensitive fluorescence-based spectroscopy technique, we measured non-degenerate two-photon absorption cross-sections (ND-TPACS) of several commonly used fluorophores and generated 2-dimensional ND-TPACS maps. We observed that the shape of the measured ND-TPACS spectra follows the spectra of the degenerate two-photon absorption cross-sections (D-TPACS). However, ND-TPACS are higher in magnitude, which is predicted by the “resonant enhancement” phenomenon. Therefore, we show that ND-TPACS spectra are predictable from the corresponding degenerate D-TPACS spectra under consideration of resonant enhancement. Predictability of ND-TPACS spectra is an important finding that helps choosing the optimal combination of wavelengths for ND-TPE of a given fluorophore without prior experimental measurement of ND-TPACS.

Paper Details

Date Published: 9 September 2019
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Proc. SPIE 11122, Ultrafast Nonlinear Imaging and Spectroscopy VII, 111220V (9 September 2019); doi: 10.1117/12.2530423
Show Author Affiliations
Sanaz Sadegh, Univ. of California, San Diego (United States)
Mu-Han Yang, Univ. of California, San Diego (United States)
Christopher G. L. Ferri, Univ. of California, San Diego (United States)
Martin Thunemann, Univ. of California, San Diego (United States)
Payam A. Saisan, Univ. of California, San Diego (United States)
Anna Devor, Univ. of California, San Diego (United States)
Yeshaiahu Fainman, Univ. of California, San Diego (United States)


Published in SPIE Proceedings Vol. 11122:
Ultrafast Nonlinear Imaging and Spectroscopy VII
Zhiwen Liu; Demetri Psaltis; Kebin Shi, Editor(s)

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