Multiphoton-absorbing organic materials for microfabrication, emerging optical applications and non-destructive three-dimensional imaging

Non-resonant two-photon absorption (TPA) can be defined as the simultaneous absorption of two photons, via a virtual state, in a medium. TPA exhibits a quadratic dependence of absorption on the incident light intensity, resul ting in highly localized photoexcitation. Recent developments in the design and synthesis of efficient, stable TPA organic materials are discussed. Mi crofabrication via two-photon induced free radical polymerization of acryla te monomers and cationic polymerization of epoxide monomers was accomplishe d using commercially available photoinitiators, and also a custom-made comp ound possessing high two-photon absorptivity. Two-photon facilitated photoi somerization of a fulgide in solution and in a polymer thin film demonstrat ed two-photon induced photochromism and its application in interferometric image recording, respectively. Greatly enhanced signal-to-noise ratios and resolution were achieved in the non-destructive three-dimensional two-photo n fluorescence imaging of a polymer-coated substrate versus conventional si ngle-photon laser scanning confocal microscopic imaging. Multifunctional TP A organic materials and fabrication of functional microstructures are also discussed. Copyright (C) 2000 John Wiley & Sons, Ltd.