One‐ and Two‐Photon Absorption: Physical Principle and Applications

Abstract

We introduce the principle and applications of one‐photon absorption (OPA) and two‐photon absorption (TPA) controlled by external electric fields. The physical mechanism of OPA and TPA are firstly introduced, which can visually promote thoroughly understanding of principle and physical analysis. Secondly, the applications of different molecules in OPA and TPA with and without external electric field are introduced in detail. The effect of the external electric field on the charge transfer during the absorption process is also exemplified. Furthermore, the external electric field on the molecular orbital wave function is visualized through the charge transfer process in the excited state transitions. The purpose of this review is to deepen the understanding of the types of charge transfer under linear and non‐linear absorption in different systems.

Interpretable Machine Learning of Two-Photon Absorption

“…1,2 TPA has been crucial in many technologies, including upconverted laser 3,4 , two-photon bioimaging [5][6][7] , two-photon photodynamic therapy [8][9][10] , and three-dimensional printing [11][12][13] . A range of molecules and materials with high TPA cross sections (TPACS, ) were discovered, [14][15][16][17] as determined by the Z-scan 18 and two-photon excited fluorescence methods 19 .…”

Predicting Two-Photon Absorption Cross Sections with Experimental Accuracy Using Only Four Molecular Features Revealed by Interpretable Machine Learning

“…1, 2 TPA has been crucial in many technologies, including upconverted laser 3,4 , two-photon bioimaging [5][6][7] , two-photon photodynamic therapy [8][9][10] , and three-dimensional printing [11][12][13] . A range of molecules and materials with high TPA cross sections (TPACS, ) were discovered, [14][15][16][17] as determined by the Z-scan 18 and two-photon excited fluorescence methods 19 .…”

Control and Modulation of Photoinduced Charge Transfer in a Rigid Donor–Bridge–Acceptor System by Electric Fields

“…Since then, in order to commemorate her, the unit of the TPA cross section is represented by GM (1 GM ≡ 10 –50 cm 4 ·s·photons –1 ·molecule –1 ). TPA is a nonlinear optical effect. , When two photons at different frequencies or the same frequency act on atoms or molecules, energy conversion occurs between optical radiation and matter. After the substance absorbs the photons generated by the high-intensity laser excitation, the transition process happens in two steps: (1) the transition from the ground state to the intermediate virtual state and (2) the further transition to the final excited state .…”