Nanoscale physics

Plasmon resonance in the prism structure with sinusoidal grating
Vernyhor O.L.
 Department of Electronic Engineering, Lviv Polytechnic National University, S.Bandery str.12, Lviv, 71013, Ukraine. 
E-mail: oleksandr.l.vernyhor@lpnu.ua

Nowadays, there is an increasing interest in optimizing plasmon sensors based on prisms by forming periodic structures on them [1,2]. Plasmon resonance in the prism structure, on the surface of which a sinusoidal relief profile with silver film, has been researched by the finite element method (FEM). The angular sensitivity was calculated for the wavelength 1064 nm.  At this wavelength for silver, the refractive index is 0.087829 and the extinction coefficient is 7.6761 [3]. The refractive index of the prism is 1.76. The period of the sinusoidal grating is 150   nm. Resonance angles for two refractive indices of the research medium n1 = 1.333 and n2 = 1.334 were determined. The angular dependence of absorption and reflection is obtained in the structure heights ranging from 0 to 100 nm.
It was determined that the sensitivity increases from 1 to 2.8 rad with increasing structure height. However, increasing the height leads to a degradation of the resonant properties of the structure, which is expressed in a reduction in resonant absorption.  Also, with the increasing height of the structure, there is an expansion of the resonance curve from 0.0018 to 0.0161 rad. This suggests that the optimal selection of the height of the structure can improve sensitivity.

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