Highly Active Two-Photon Dyes: Design, Synthesis, and Characterization toward Application

A series of compounds with systematically varied molecular structures which exhibit very large effective two-photon cross sections has been synthesized and characterized in solution using a nonlinear transmission technique. The general structure of these compounds can be categorized into two basic structural families: acceptor/donor/donor/acceptor and donor/bridge/acceptor. This study attempts to determine certain molecular structure/effective two-photon absorption relationships by careful characterization and as a function of systematically varied changes in the organic structure of the dye molecules. Such information can be useful in the design of more efficient two-photon dyes for imaging and power-limiting applications. The results of the study indicate that with the incorporation of certain combinations of structural elements, dyes can be synthesized which have greatly increased effective cross sections as high as 152.5 × 10^-48 cm⁴ s/photon molecule in benzene solution at 800 nm using 8 ns pulses. This value is orders of magnitude higher than commercially available organic dyes measured at the same wavelength. Although the process is thought to involve a combination of two-photon absorption and excited state absorption phenomena, the information gathered from these new families of dyes has provided an important first step in producing improved materials for use in many different two-photon technology application.