Abstract-Ferromagnetic resonance isolator based on a photonic crystal structure with terahertz vortices

Gianni Portela, Victor Dmitriev, Daimam Zimmer,

https://link.springer.com/article/10.1007%2Fs11107-019-00871-x

A new terahertz isolator based on the ferromagnetic resonance effect is suggested and analyzed. A two-dimensional photonic crystal consisting of a square lattice of gallium arsenide rods has been employed in the design of the device. Incident electromagnetic waves interact with one magnetized ferrite rod and two stubs inserted in the photonic crystal structure, generating a vortex-like field profile in the ferrite rod. Electromagnetic signals propagating in the forward direction are transmitted with low insertion losses, while their propagation in the backward direction is not allowed due to the high losses of the ferrite rod operating at the ferromagnetic resonance regime. Computational simulations show that the operating bandwidth is equal to 0.87 GHz around the central frequency 106.6 GHz. In this frequency band, the insertion losses are lower than − 1.68 dB, the reflection levels are better than − 16 dB, and the isolation levels are greater than − 15 dB.

Abstract-Dynamically controllable graphene terahertz splitters with nonreciprocal properties

Victor Dmitriev and Wagner Castro

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-58-24-6513

Two novel graphene-based nonreciprocal four-port splitters for the terahertz region are proposed. The input power is divided between two output ports, whereas the input port is isolated from the output ports due to the presence of the fourth port. The splitters consist of a circular graphene resonator and four graphene waveguides coupled to the resonator. These elements are placed on the two-layer dielectric substrate. The central part of the splitter is under a biasing DC magnetic field normal to the graphene layer. The surface plasmon-polariton wave in the input port excites the dipole resonance in the resonator. The splitters have the following parameters: the input power is divided between two output ports almost equally with −4.4  dB$-4.4\mathrm{dB}$. The input port is isolated from two output ports by −15  dB$-15\mathrm{dB}$. The bandwidth is 4.0% with a central frequency of 7.4 THz. The biasing DC magnetic field is 0.8 T, and the Fermi energy of graphene 𝜖𝐹=0.15  eV${ϵ}_F=0.15\mathrm{eV}$. Changing the Fermi energy by electrostatic gating allows one to dynamically control the central frequency of the splitters.

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