Title: Pockels effect of water in the electric double layer at the interface between water and transparent electrode
Authors: Tokunaga, Eiji
Nosaka, Yugo
Hirabayashi, Masashi
Kobayashi, Takayoshi
Adv Ultrafast Laser Ctr
Keywords: water;pockets effect;optical nonlinearity;electric double layer;indium oxides;solid-liquid interfaces;semiconducting surfaces;metallic surfaces;ITO;indium tin oxides;refractive index;electrolyte;lock-in detection;space charge layer;transmission spectrum;field effect;visible/ultraviolet absorption spectroscopy;non-linear optical methods;interference
Issue Date: 1-Feb-2007
Abstract: We have obtained the first experimental evidence for the Pockets effect of water, which is induced by a high electric field in the electric double layer (EDL) on the water transparent electrode interface. The electric-field induced energy shift of the visible interference fringes of a 300 nm indium-tin-oxide (ITO) electrode layer is observed, indicating a negative refractive index change at the interface. Numerical calculation reproduces well the experimental observation, showing that the signal mainly originates from water in the EDL. The Pockets constants of water are estimated to be r(33) = 5.1 x 100 pm/V and r(13) = 1.7 x 100 pm/V. The large anisotropy of the Pockets effect of water is deduced from the incidence angle dependence of the p-polarization signal. At the same time, the ITO shows a blue shift of the band gap in the UV due to the band population effect in the space charge layer. The plasma frequency in the near IR is also expected to increase due to the band population effect, since the ITO has a high doped carrier population close to metal. A negative refractive index change in the ITO space charge layer is induced from both effects, but its effect on the signal is estimated to be much smaller than that of the negative refractive index change of water in the EDL. (c) 2006 Published by Elsevier B.V.
URI: http://dx.doi.org/10.1016/j.susc.2006.11.001
ISSN: 0039-6028
DOI: 10.1016/j.susc.2006.11.001
Volume: 601
Issue: 3
Begin Page: 735
End Page: 741
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