Study of the electric and magnetic response of random Split Ring Resonators

Date
2021-12
Authors
Bhattarai, Rabindra
Major Professor
Dalal, Vikram
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NA, NA
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Abstract
A metamaterial is an artificial material engineered to have the desired electric and magnetic response not available in nature by arranging subwavelength structures in definite patterns. Such unit structures are inhomogeneous at the microscopic level, but the array itself can be described by homogenous effective parameters at the scale of the wavelength of incident light. With proper tuning of electric and magnetic responses, we can control the propagation of the EM waves. Electric metamaterial, used in tuning electric response, is realized by periodically arranging thin metallic wires, whereas magnetic metamaterial is realized by the periodic arrangement of the sub-wavelength structure called Split Ring Resonator. SRR give rise to magnetism by the resonant current through it. Most SRR are fabricated using a top-down approach like electron-beam lithography, which has a serious issue with scalability. The bottom-up approach, like DNA-assisted lithography, can be very effective in fabricating a large number of SRR. Due to the stochastic nature of self-assembly and growth process, SRR fabricated using this technology possesses morphological disorder and surface roughness. The robustness of optical response against these disorders in SRR is studied using electromagnetic simulations. Aggregated- random spheres model is used to create SRR. SRR is bianisotropic. i.e., the magnetic and electric dipole moments can be excited by external electric and magnetic fields and are related by polarizability dyadic. Polarizations and magnetization due to the external excitations are computed to retrieve polarizabilities, ultimately fitting to function assuming equivalence of SRR and LCR circuit. The distribution of these fitted parameters is studied.
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