Hyperbolic Phonon-Plasmon Modes in Grounded Graphene-hBN Heterostructures for Mid-Infrared Applications

In recent years, the hybridization of hyperbolic van der Waals heterostructures with plasmonic two-dimensional nano-materials is one of the interesting research areas at THz frequencies due to the coupled features of the hybrid structure. This article investigates the propagation of tunable surface phonon-plasmon polaritons in grounded hybrid graphene-hexagonal Boron Nitride (hBN) heterostructures. An analytical model is presented for the proposed structure, by applying the boundary conditions for the electromagnetic components in the various regions, to derive an exact dispersion relation. The structure is simulated and the results are reported in the upper Reststrahlen band. A good agreement is seen between simulation and analytical results, which shows the high accuracy of our mathematical relations. The tunability of the heterostructures is shown by studying the effect of chemical potential on the performance of the structure. A high value of the figure of merit, i.e. FOM=190, is reported at the frequency of 48.3 THz. The presented study can open the way for the design of novel THz devices for future nano-plasmonic applications.Comment: 13 pages, 8 figure

Theoretical analysis of hybrid surface plasmon polaritons in plasma-based elliptical structures with graphene layers for THz applications

In this article, tunable surface plasmon polaritons (SPPs) in graphene-based elliptical waveguides containing gyro-electric layers are investigated. The general structure has an elliptical cross section, where each gyro-electric layer is surrounded by two graphene layers. The DC magnetic bias is applied on the z-axis. By writing Maxwell’s equations inside the gyro-electric medium and applying boundary conditions, closed-form general relations are obtained for electromagnetic components of SPP waves. As a special case, a new plasma-based elliptical structure with double-layer graphene is studied in this paper. The figure of merit (FOM) for this waveguide can be varied by changing the magnetostatic bias and the chemical doping. At the frequency of 40 THz, the FOM of 139 for this waveguide is reported for the B = 1 T and μc = 0.9 eV. Ability to adjust and tune the propagating properties of SPPs in hybrid graphene-plasma elliptical structures can be exploited for the design of new plasmonic components in the THz spectral region

Design and construction of ferrite waveguide circulator with short wall in S band

Abstract One of the most important components in the radar and microwave industry that provides transmitting and receiving features for an antenna at the same time is called a circulator. Ferrite circulators are passive three‐port devices in which the RF or microwave signal is transmitted from one port to other port without leakage to the third port. One of the main disadvantages of these waveguide elements is their large dimensions and especially their height, which cannot be used in some systems due to the limited workspace. This paper solves this problem by exploiting an incomplete wall waveguide to reduce the height of the circulator by 50%. These changes always reduce the frequency bandwidth of the element, the proposed technique optimizes the dimensions of the ferrite and its magnetic characteristics and increases the bandwidth to 400 MHz in 2.9 GHz, which is the ideal bandwidth required by many radar systems that have been reached. The ferrite circulator designed and built in this article has a port with a width of 72.13 mm and a height of 17 mm in the S‐band. The method results in a low insertion loss which is less than 0.5 decibels and a high isolation which created more than 20 decibels. The designed and optimized elements have been implemented and the test results verify the theoretical results