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Femtosecond Transient Holography

While at Los Alamos National Laboratory I studied femtosecond transient holography in conjugated polymer blends and superlattices, using tunable, nondegenerate four-wave mixing. Combined with spectral transient absorption studies, these experiments determine the complex photoinduced index of refraction over the photon energy range from 1 to 3 eV. The samples we use include several luminescent polymers from the poly-phenylene-vinylene family, as well as charge transfer blends with soluble methanofullerenes, and donor-acceptor superlattices formed by ionic self-assembly. Diffraction efficiencies of several percent for a single femtosecond pulse are achieved and, by controlling the degree of charge transfer, we can tune the time constant over the range from 1 to 100 ps. This represents a potential holographic information processing density up to 12 orders of magnitude higher than other holographic nonlinear optical materials. Click here to see publications.

Photogeneration mechanisms in conjugated polymers

I also studied photogeneration mechanisms in conjugated polymers through femtosecond polarized transient absorption experiments. The type of photoexcitation created depends on the intensity of the incident light. By monitoring the dichroic ratio of the transient absorption as a function of the intensity of the photoexciting light pulse, we can discriminate between the various types of fundamental photoexcitations created. Click here to see publications.

For a survey of some of the physics, experiments, and lasers involved in ultrafast physics and nonlinear optics, click here.