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Bulletin of Pure and Applied Sciences- Physics (Started in 1982)
eISSN: 2320-3218
pISSN: 0970-6569
Impact Factor: 5.195 (2017)
DOI: 10.5958/2320-3218
Editor-in-Chief:  Prof. Madan jee,
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Bulletin of Pure and Applied Sciences- Physics (Started in 1982)
Year : 2019, Volume & Issue : BPAS-Physics 38D(1), JAN-JUN 2019
Page No. : 46-50, Article Type : Original Aticle
Article DOI : 10.5958/2320-3218.2019.00007.1 (Received on 29.03.2019 Accepted on 04.05.2019)

Impedance for Wave Guiding Devices from the Microwave Frequency Regime to Optics and Plasmonics

Abdul Sattar Alam* & Ashok Kumar
Author’s Affiliation : Abdul Sattar Alam Research Scholar, University Department of Physics, B.N. Mandal University, Laloo Nagar, Madhepura, Bihar 852113, India E-mail: [email protected] Ashok Kumar University Department of Physics, B.N. Mandal University, Laloo Nagar Madhepura, Bihar 852113, India E-mail: [email protected]

Corresponding Author : Abdul Sattar Alam, Research Scholar, University Department of Physics, B.N. Mandal University, Laloo Nagar, Madhepura, Bihar 852113, India,
E-Mail:-[email protected]


We have derived expressions that generalized the impedance concept for wave guiding devices from the microwave frequency regime to optics and plasmonics. Our expressions were based on electromagnetic eigen modes that are excited at the interface of a structure. Impedance in electromagnetic wave theory is the ratio of the electric and magnetic field strength. The ratio between the electric and magnetic field is not constant over the cross section in most devices. This caused several suggestions using averaged or integrated fields which were heuristically proposed for a manifold of photonic structures not only waveguides. The area of photonic crystals were several such heuristic approaches excited until it was proven that the so called Bloch impedance, the ratio of the surface averaged fields was analytically correct solution, provided that the photonic crystal operates only in its fundamental modes. Electromagnetic response closely resembles the solution in the quasistatic limit. Plasmonic metal-insulator-metal waveguide and a waveguide at microwave frequencies facilitated the use of traditional impedance for this kind of structure in plasmonics. For this we required lumped circuit parameters to the radio frequency domain. Impedance definition must correctly describe the reflection that occurs at the boundary between two different structures. We analysed the reflection at an interface of impedance discontinuity i.e. between two different structures. A plasmonic insulator-metal-insulator waveguide characterized by referential impedance; illustrates another photonic structure. We have used Bragg reflector, i.e periodic corrugations in a metal film which intended to describe impedance. In case of circuit theory; we considered as part of a photonic network. Our approach was based on a decomposition of the electromagnetic fields into eigenmodes. We have chosen it because the relatively strong loss in the metal that prevented the use of many radio frequency derivations and the open boundary condition that made it possible to find suitable analogies to voltage and current. We observed that the impedance for the reciprocity based overlap of eigen modes. We found that applicability of simple circuit parameters ends and how the impedance can be interpreted beyond any particular point. The unconjugated reciprocity framework set up to solve for the interface reflection coefficient of the different electromagnetic eigen modes. This rigorous expression is linked to the relative impedance of the discontinuity between the two structures which yields a very general expression for the modes’ impedances. Our obtained results were found in good agreement with previously observed theoretical and experimental works.


Impedance, waveguide, microwave, plasmonics, electromagnetic, eigen modes, heuristically, photonics, radio frequency.
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