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

Abstract

Two photons are better than one: This principle applies to a wide range of applications, ranging from engineering to physiology. Recent advances in our understanding of the phenomenon of two-photon absorption (see picture) and in the design of two-photon dyes are rapidly increasing the scope of this field. 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.