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Potential-sensitive dyes have been extensively used to probe the electrical environment in biological membranes due to changes in its linear and nonlinear optical properties as a function of the local electric field. Ratiometric fluorescence, two-photon excited fluorescence and second harmonic generation have all been applied to study biological cell and membrane systems. Mechanism and sensitivity studies for these potential-sensitive dyes have become popular due to the increasing biological needs. In this book, fluorescence-free time-correlated single photon counting hyper Rayleigh scattering has been used to determine the hyperpolarizability of the potential-sensitive dyes. Experiment results are in agreement with quantum chemical calculations. The polarity-dependent solvent effects of linear absorption and hyper-Rayleigh scattering in solution of potential-sensitive dyes is combined together to analyze the spectral dependence of the sensitivity to the local environment. Studies of dye monolayer have been tried and high resolution fluorescence near-field scanning optical microscopic imaging with has been performed.

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Haowen Li earned a B.S. in physics at Fudan University in 1997, a M.S. in optical science at Shanghai Jiao Tong University in 2000 and a Ph.D. in physics from Case Western Reserve University in 2007. His research interest includes nonlinear optics, biomedical imaging and ultrafast laser applications. He is a member of OSA, SPIE, and Sigma Xi.

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