We have synthesized a series of dendrimers, generations 1 through 3, functionalized with two-photon absorbing (TPA) chromophores at their chain ends. These novel TPA materials were characterized with respect to their one- and two-photon absorption properties.

No abstract

Two-photon processes have recently received considerable attention, as they offer opportunities for both fundamental research and technological applications. In this paper, we illustrate both of these opportunities by reporting on a study of two-photon properties and discussing one specific application of a new chromophore, tris[4-(7-benzothiazol-2-yl-9,9-diethylfluoren-2-yl)phenyl]amine . This new compound exhibits a large two-photon absorptive cross section and, more importantly from the application point of view, a high photochemical/photothermal stability. The nonlinear optical properties of an AF-350 solution were studied with ∼800-nm laser pulses in both nanosecond and femtosecond regimes. The two-photon excited fluorescence spectrum and temporal behavior were compared with the corresponding results obtained for one-photon excitation. There is an ∼11-ps delay between an ultrashort pump pulse and the first peak of the two-photon induced fluorescence signal, whereas no delay was measured between the pump pulse and the first peak of the one-photon induced fluorescence. The measured effective two-photon absorption (TPA) cross section is σ 2 ) (151 ( 23) × 10 -20 cm 4 /GW for 7-ns, 810-nm laser pulses and σ 2 ) (0.61 ( 0.02) × 10 -20 cm 4 /GW for 135-fs, 796-nm laser pulses. One specific application reported here is the spatial-profile reshaping and smoothing of a focused laser field.

An approach using an as-formed solid bulk sample containing a blend of photocurable and thermally curable epoxies together with a highly efficient two-photon excitable fluorophore is demonstrated for in situ fabrication of three-dimensional optical circuitry with a precise control of dimension and spatial locations. Confocal volume images of a 1×2 splitter and a grating coupler are shown. End-fire coupling of a He–Ne laser beam into the 1×2 splitter has been achieved.

This paper presents a molecular design for a two-photon absorbing structure, which contains a two-dimensional molecular architecture with four arms and one bridging unit, each of these segments having an extended π-conjugation and capable of producing twophoton absorption in different spectral ranges. Two chromophore units of a triphenylamine derivative dye, (N, N-di[4-{4-(5-[4-tert-butylphenyl]-1,3,4-oxadiazol-2-yl)styryl}phenyl]amino)benzene, were linked with a π-conjugated di-2-thienylethenylene bridging unit to form a new multibranched compound, bis(5-[4-{N,N-di(4-[4-{5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl}styryl]phenyl)amino}styryl]thien-2-yl)ethenylene. Linear absorption spectra and luminescence spectra of the component and the multibranched chromophores revealed a hypochromic effect for the multibranched dye. A very effective energy transfer from the excited arm units to the π-conjugated bridging unit is observed. The two-photon cross-sections were measured using the femtosecond Z-scan technique at several excitation wavelengths in the 620-800 nm range. Comparing the nonlinear absorption coefficients observed for the constituent chromophore dyes with that for the multibranched compound, we found that the arm units make the dominant contribution to the two-photon absorption when the wavelength of excitation is longer than 720 nm.