Nanoplasmonics and surface enhanced spectroscopy

Resonance of surface-localized plasmons in a system of periodically arranged copper and aluminum nanowires on a dielectric substrate 
 V.V. Fitio1, I.Y. Yaremchuk1, O.L.Vernyhor1,  Y.V. Bobitski 1,2

1 Department of Fotonics, Lviv Polytechnic National University,
C. Bandera str. 12, Lviv-71013, Ukraine 
E-mail: v.m.fitio@gmail.com
2 Faculty of Mathematics and Natural Science, University of Rzeszów, 
Rejtan’s str. 16b, Rzeszów-35-959, Poland
Plasmon resonance in the gratings on base of copper or aluminum periodic square nanowires has been researched by rigorous coupled wave analysis (RCWA). Cross-sections of the nanowires are selected 30×30 nm2 and 50×50 nm2. Period of such structure was varied from 0.06 µm to 0.25 µm. Modified RCWA has been used for better convergence [1]. The spectral dependences of absorption, transmission and reflectance were obtained in wavelength range from 0.1 to 0.7 µm. In additional, a field distribution was calculated on the interfaces grating-air and grating-substrate. It is determined, that absorption maximum is at wavelengths 0.6 µm for copper and 0.12 µm and 0.22 µm for aluminum gratings. 
The resonance peak is observed in ultraviolet wavelengths region for aluminum nanowires and is splitted on two peaks. The spectral characteristic of the plasmon resonance for copper nanowires is similar to the corresponding characteristic of the gold nanowires. However, it is shifted to the region of long wavelengths. From the viewpoint of the convergence of the calculation results for the aluminum nanogratings, it is necessary to use more coupled waves than for copper. As a result, electromagnetic fields on resonance wavelengths which occur in aluminum nanogratings are significant higher than in copper nanogratings.
In generaly, it can be concluded that the spectral characteristics of the aluminum nanowires are close to the spectral characteristics of the silver nanowire; in case of the copper nanowires the spectral characteristics are qualitatively similar to the ones for the gold nanowires.

1.	Fitio, V., Yaremchuk, I., Vernyhor, O., Bobitski, Y. Resonance of surface-localized plasmons in a system of periodically arranged gold and silver nanowires on a dielectric substrate.// Applied Nanoscience.- 2018. - P. 1-10.