Nanoplasmonics and surface enhanced spectroscopy
Modelling the spectra of surface plasmons in an ITO nano-ribbon gratings
Reshetnyak V.Yu.1, Zadorozhnii V.I.1, Pinkevych I.P.1, Bunning T.J.2, 
      Evans D.R.2
1 Physics Faculty, Taras Shevchenko National University of Kyiv, 01601 Kyiv, Ukraine.
E-mail: v.i.zador@gmail.com
2 Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, OH 45433, USA.

Indium Tin Oxide (ITO) belongs to the transparent conductive oxides, which have tunable optical properties. Such oxides are considered as alternative to noble metals in different plasmonic device applications [1, 2]. We theoretically studied the reflection and transmission of the ITO nano-ribbon grating placed between a nematic liquid crystal (LC) layer and an isotropic dielectric substrate. An incident electromagnetic wave excites the surface plasmons (SPs) in the ITO ribbons. Using the Drude model for ITO ribbons conductivity, we calculated reflection and transmission of this system under the assumption that the ITO nano-ribbons can be treated as a 2D structure. In the infrared (1-5) region we found the maxima/minima in the reflection/transmission spectra, which are related to the excitation of the SPs in the ITO nano-ribbons.
We show that a change of the 2D electron concentration in the ITO ribbons leads to a shift of the reflection/transmission peaks and the change of their magnitude. It is also shown that the magnitude of the reflection/transmission peaks depends on the electron relaxation time and the LC orientational state. The obtained results can be used for designing new types of photonic structures based on plasmonic properties of the ITO nano-gratings.

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