Non-Degenerate Two-Photon Absorption of Fluorescent Protein Chromophores

26 December 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Two-photon absorption (2PA), where a pair of photons are absorbed simultaneously, is recognized as a potent bioimaging technique, which depends on the quantified 2PA probability, defined as cross-section (σ2PA). The absorbed photons either have equivalent (ω1 = ω2) or different frequencies (ω1 ≠ ω2), where the former is degenerate 2PA (D-2PA) and the latter is non-degenerate 2PA (ND-2PA). ND-2PA is of particular interest since it is a promising imaging technology with flexibility of photon frequencies and enhanced cross-sections, however, it remains a relatively unexplored area compared to D-2PA. This work utilizes time-dependent density functional theory (TD-DFT) and second-order approximate coupled-cluster with the resolution-of identity approximation (RI-CC2), for the excitation from S0 to S1, to investigate σD-2PA and σND-2PA of fluorescent protein chromophore models. Interestingly, comparison of the CAMB3LYP and RI-CC2 computations show a qualitative trend in the computed σND-2PA improvements and vertical excitation energy, ΔE. As expected, the computed values of σND-2PA are quantitatively larger than σD-2PA, where chromophores with the largest values of σD-2PA show greater potential for σND-2PA improvement. Anionic chromophores demonstrated improvements up to 14%, while substantial enhancements were observed in neutral chromophores with some achieving a 30% increase.


Two-Photon Absorption
Fluorescent Protein Chromophores
Response Theory

Supplementary materials

Supporting Information
Supporting Information for “Non-Degenerate Two Photon Absorption of Fluorescent Protein Chromophores”


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.