TY - JOUR T1 - Spheroidal-Shaped Nanoshell Description for Optical Properties of Metallic Nanorings TT - Spheroidal-Shaped Nanoshell Description for Optical Properties of Metallic Nanorings JF - opsi JO - opsi VL - 21 IS - 0 UR - http://opsi.ir/article-1-834-en.html Y1 - 2015 SP - 1619 EP - 1622 KW - Extinction KW - Localized Surface Plasmon Resonance KW - Nanoring KW - Polarizabilty N2 - The optical properties of a single metallic nanoring (NR) have been analyzed according to variation of thickness, inner, and outer radius effects on the extinction cross section spectrum. It is shown that, by considering constant values for inner radius and thickness, a new phenomenon in optical properties is observed. More specifically, increasing the outer radius for the aspect ratio (i.e. outer radius/thickness) of less than 3.2, results in a blue-shift in the extinction spectrum, while for the aspect ratio of greater than 3.2 a red-shift for the LSPR (localized surface plasmon resonance) wavelength occurs. Moreover, by taking constant outer radius and thickness, increasing the inner radius results in a blue-shift for the extinction spectrum. Nonetheless, increasing the thickness leads to a blue-shift for the maximum peaks of the extinction spectrum. It has been shown that the optical properties for a gold NR can be described well through the quasi-static theory of a spheroidal shaped metallic nanoshell, while the previous theory for the NRs known as “slab like model” could not justify these properties. The analytic results supports the numerical simulations. M3 ER -