Dianne McCord-Maughon

Three-dimensional microfabrication using two-photon-activated chemistry

Photochemical reactions which can be activated by the simultaneous absorption of two photons provide a means for single-step fabrication of complex 3D microstructures. These types of structures are needed for a wide range of applications, including microfluidics, electrooptics, and micro-electromechanical systems. We have shown that chromophores can be engineered to have both large two-photon absorptivities as well as an efficient means for activating chemical processes, such as radical polymerization, subsequent to the photoexcitation. Chromophores designed following this strategy two-photon-activate the radical polymerization of acrylates at lower incident laser powers than conventional UV initiators. Efficient two-photon photopolymer resins based on these chromophores were used in the fabrication of complex microarchitectures, such as photonic bandgap structures and tapered waveguides. We have devised a strategy which allows this approach to be extended to other chemical systems.

Theoretical Design of Organic Chromophores with Large Two-Photon Absorption Cross-Sections

Design strategies and structure-property relationships for two-photon absorption in conjugated molecules are described on the basis of correlated quantum-chemical calculations. We first focus on stilbene derivatives with centrosymmetric structures. We found that derivatization of the conjugated molecule with electroactive groups in a quadrupolarlike arrangement leads to a large increase in the two-photon absorption cross section, δ. Quantum-chemical description provides rich insight into the mechanisms for the two-photon absorption phenomenon.

Two-photon spectroscopy of symmetric donor/acceptor substituted conjugated molecules

Summary form only given. The design of two-photon absorbing chromophores for applications such as optical limiting, fluorescence imaging and microfabrication, relies on the availability of detailed structure-property relationships for the two-photon response. In this presentation we will discuss the two-photon absorption spectra for donor-/spl pi/-donor (D-/spl pi/-D), donor-/spl pi/-acceptor-/spl pi/-donor (D-A-D) and acceptor-/spl pi/-donor-/spl pi/-acceptor (A-D-A) molecules (where /spl pi/ is a biphenyl, a polyenic-type or bis(styryl)benzene-type /spl pi/-bridge), which have been measured using the two-photon induced fluorescence method.