Three-photon absorbing materials: characterization and applications

Recent successes in developing two-photon absorption (2PA) materials and applications have now created significant interest in exploring three-photon absorption (3PA) based novel optical materials and new applications. 3PA-based techniques may exhibit two major advantages: (1) much longer IR wavelengths (1.2-1.7 mum) can be used, and (2) much better beam confinement (resolution) can be achieved owing to the cubic dependence of nonlinear absorption on the local intensity of the excitation IR light. We have demonstrated efficient three-photon excitation in a number of nonlinear organic materials. developed at our Institute or in cooperation with other research groups. The 3PA capability of a given material can be estimated by measuring the 3PA coefficient (or cross-section) at a given excitation wavelength or as a function of the excitation wavelength. The 3PA-active materials can be either highly fluorescent or non-fluorescent. Applications of novel and highly efficient three-photon absorbing materials include (i) three-photon pumped (3PP) and frequency upconverted lasing, (ii) 3PA-based optical power limiting and stabilization, (iii) 3PA-based bio-imaging via IR to visible conversion, and (iv) 3PA-associated 3D data storage and microfabrication. Some recent experimental results of 3PP lasing as well as 3PA-based power limiting are briefly presented.