Browsing by Author "Cooper, K. L."

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    High-performance photovoltaic behavior of oriented purple membrane polymer composite films
    Zhang, L. M.; Zeng, T. Y.; Cooper, K. L.; Claus, Richard O. (Cell Press, 2003-04-01)
    The photovoltaic behavior of films in which bacteriorhodopsin molecules are embedded in a polyvinyl alcohol matrix has been investigated by using both pulsed laser excitation and regular light illumination. Response times as short as milliseconds, photocurrents as great as 120 muA/cm(2), and photovoltages as large as 3.8 V have been obtained. A theoretical model has been developed and used to extract several physical parameters and fit the experimental results. Some important intrinsic parameters have been obtained. Theoretical results indicate that the average displacement of the excited protons is on the order of several tens of microns. Other curve fits show that photocurrent and photovoltage increase linearly with external field, but increase exponentially with flash power. These theoretical models and results can be extended to other kinds of photoactive polymeric materials.
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    In-Fiber Reflection Mode Interferometer Based on A Long-Period Grating For External Refractive-Index Measurement
    Kim, D. W.; Zhang, Y.; Cooper, K. L.; Wang, Anbo (Optical Society of America, 2005-04-01)
    We present two novel schemes for refractometry based on a long-period fiber grating- (LPG-) based Michelson interferometer. These schemes are designed to overcome the measurement dependence of previously demonstrated LPG-based refractometry on the immersion depth. The first utilizes an unshielded LPG and the second, a shielded one. Both schemes were tested over a certain refractive-index range, and the measurement of glucose concentration in water was experimentally demonstrated. In addition, the temperature sensitivity of the two schemes is discussed. (c) 2005 Optical Society of America.
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    Label-free DNA sequence detection using oligonucleotide functionalized optical fiber
    Wang, X. W.; Cooper, K. L.; Wang, Anbo; Xu, J. C.; Wang, Z. A.; Zhang, Y.; Tu, Zhijian Jake (AIP Publishing, 2006-10-01)
    The authors present a label-free method for direct detection of deoxyribonucleic acid (DNA) sequences. The capture DNA is immobilized onto the surface of a silica optical fiber tip by means of the layer-by-layer electrostatic self-assembly technique. Hybridization of target DNA with complementary capture DNA increases the optical thickness of the fiber tip. This phenomenon can be detected by demodulation of the spectrum of a Fabry-Perot cavity fabricated in the optical fiber. Experimental results demonstrate sequence specificity and sensitivity to nanogram quantities of target DNA sequences with short (similar to 5 min) hybridization time. (c) 2006 American Institute of Physics.