Two‐Photon Absorption and the Design of Two‐Photon Dyes

Abstract

Two-photon absorption has important advantages over conventional one-photon absorption, which has led to applications in microscopy, microfabrication, three-dimensional data storage, optical power limiting, up-converted lasing, photodynamic therapy, and for the localized release of bio-active species. These applications have generated a demand for new dyes with high two-photon absorption cross-sections. This Review introduces the theory of two-photon absorption, surveys the wide range of potential applications, and highlights emerging structure-property correlations that can serve as guidelines for the development of efficient two-photon dyes.

Identifying diamagnetic interactions in scattering and nonlinear optics

“…Two-photon absorption (TPA) is a well-studied process, widely used in nonlinear spectroscopy [19]. Single-beam TPA is a suitable process to exhibit how a scalar diamagnetic contribution can become both readily identifiable and dominant compared to other multipole contributions.…”

Multi-photon excitation in uncaging the small molecule bioregulator nitric oxide

“…The evolution of such structure/activity design considerations has also pointed to π -conjugated quadrupolar molecules with such electron-donor and -acceptor units arranged symmetrically with respect to the centre of the molecule as having large two-photon cross sections in the NIR region [31]. This has led to a sizable effort into the development of new TPE chromophores [26,31,32], although as He and co-workers [26] pointed out, there is some difficulty in comparing the quantitative two-photon absorption cross-section values reported, since these have been measured by different techniques and under different conditions.…”

Comparison of Carbazole and Fluorene Donating Effects on the Two‐Photon Absorption and Nitric Oxide Photorelease Capabilities of a Ruthenium–Nitrosyl Complex

“…Among them, ruthenium-nitrosyl complexes have been recognized as the most promising candidates in relation to their generally low toxicity, good stability, and ability to release exclusively NO· under light irradiation, [6] taking advantage of the noninvasive and highly controllable characteristics of light. Additionally, although most NO· donors require to be irradiated in the 300-500 nm domain, the use of the two-photon absorption (TPA) technique, [7][8][9][10][11] in which the molecules simultaneously absorb two photons instead of one, allows the use of optical radiation at the double of wavelength, that is, the 600-1200 nm therapeutic window tiary amine in the carbazole unit leads to redshifted chargetransfer transitions towards the electron-withdrawing Ru-NO fragment and hence enhanced two-photon absorption (TPA) properties. In contrast, the quantum yield of the NO· photorelease process is lower for the carbazole-containing complex.…”

“…Indeed, it has been shown that increasing the "push-pull" character of the π-conjugated skeleton usually leads to an increase in σ TPA in dipolar molecules. [7][8][9][10][11] Therefore, the idea of replacing the fluorenyl unit by a more donating fragment arises naturally.…”