Impedance Matching of THz Plasmonic Antennas

Plasmonic antennas with subwavelength gaps work as sensing devices for molecules for the optical and terahertz (THz) frequency range. In such a configuration, the sensing gap creates a high impedance, in contrast to the antenna itself, which is designed for low ohmic losses. Besides metals, highly d...

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Bibliographic Details
Published inJournal of infrared, millimeter and terahertz waves Vol. 40; no. 9; pp. 929 - 942
Main Authors Bettenhausen, Maximilian, Grüßing, Soenke, Hardt, Elena, Flesch, Julia, Römer, Friedhard, Chavarin, Carlos Alvarado, Klesse, Wolfgang M., You, Changjiang, Piehler, Jacob, Capellini, Giovanni, Witzigmann, Bernd
Format Journal Article
LanguageEnglish
Published New York Springer US 01.09.2019
Springer Nature B.V
Subjects
Antennas
Circuit design
Classical Electrodynamics
Computer simulation
Detection
Dipoles
Electrical Engineering
Electronics and Microelectronics
Engineering
Frequency ranges
Germanium
Graphene
High impedance
Impedance matching
Instrumentation
Plasmonics
Q factors
Resonance
Sensors
Three dimensional models
Plasmonics
Impedance matching
Germanium on silicon
Semiconductor antennas
Graphene
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Summary:Plasmonic antennas with subwavelength gaps work as sensing devices for molecules for the optical and terahertz (THz) frequency range. In such a configuration, the sensing gap creates a high impedance, in contrast to the antenna itself, which is designed for low ohmic losses. Besides metals, highly doped semiconductors can be used as plasmonic materials for the THz range, which increase the impedance of the antenna while keeping the strong electromagnetic intensity enhancement in the sensing gap. Still, a substantial impedance mismatch remains. In this paper, an approach for matching the gap to the antenna impedance is proposed. First, a germanium semiconductor slab antenna is designed for THz operation, with a dipole resonance at 4 THz. Based on an impedance analysis, an impedance matching element consisting of a graphene sheet is inserted in parallel to the gap. Employing impedance matching, a strong intensity enhancement occurs and the normal dipole mode of the plasmonic antenna is split into a symmetric one at 0.67 THz and an antisymmetric one at 4 THz. The symmetric mode provides a very high-quality factor and a substantial enhancement; furthermore, its resonance can be tuned by the Fermi level adjustment in the graphene. First designs of this structure are computed analytically with a circuit model and are verified by 3D full-wave simulations.
ISSN:1866-6892
1866-6906
DOI:10.1007/s10762-019-00613-0