Abstract-Broadband amplitude, frequency, and polarization splitter for terahertz frequencies using parallel-plate waveguide technology

A. I. Hernandez-Serrano, Daniel M. Mittleman, and Emma Pickwell-MacPherson

 (a) Schematic diagram of the proposed demultiplexer. The incoming beam impinges on the back surface of the demultiplexer forming guided modes inside the structure. The exit beam is deflected by an angle 𝜃$\theta$ which depends on the frequency of the signal and on the dimensions of the structure. The inset shows a photograph of the device. (b)–(c) Finite-element simulation at 0.3 THz when the spacing between plates is 0.8 mm for the TE1${\mathrm{T}\mathrm{E}}_1$ and TEM guided-modes, respectively.

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-45-5-1208

In this Letter, we report a broadband frequency/polarization demultiplexer based on parallel-plate waveguides (PPWGs) for terahertz (THz) frequencies. The fabrication and experimental validation of this polarization sensitive demultiplexer is demonstrated for the range from 0.2 to 1 THz. Upgrading the demultiplexer by adding a second demultiplexer stage, a fifty-fifty amplitude splitter is also demonstrated in the same frequency range. The multiplexer is based on a stainless-steel traveling-wave antenna, exhibiting strong mechanical robustness. This unique device exhibits three splitting mechanisms in the same device: amplitude, polarization, and frequency splitting. This is a significant improvement for the next generation of THz passive components for communication purposes.

Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Abstract-Optimized nonlinear terahertz response of graphene in a parallel-plate waveguide

APL Photonics

Parvin Navaeipour and Marc M. Dignam

The metallic parallel-plate waveguide with monolayer graphene inside forms the system being modelled. The inner material of the waveguide is polyolefin, and the graphene is placed at the center of the waveguide at y = b/2. The pump field propagates in the +z-direction and is polarized in the x-direction.

https://aip.scitation.org/doi/10.1063/1.5045652

Third harmonic generation of terahertz radiation is expected to occur in monolayer graphene due to the nonlinear relationship between the crystal momentum and the current density. In this work, we calculate the terahertz nonlinear response of monolayer graphene inside a parallel-plate waveguide including pump depletion, self-phase, and cross-phase modulation. To overcome the phase mismatching between the pump field and third-harmonic field at high input fields due to self-phase and cross-phase modulation, we design a waveguide with two dielectric layers with different indices of refraction. We find that, by tuning the relative thicknesses of the two layers, we are able to improve phase matching and thereby increase the power efficiency of the system by more than a factor of two at high powers. With this approach, we find that despite the loss in this system, for an incident frequency of 2 THz, we are able to achieve power efficiencies of 75% for graphene with low Fermi energies of 20 meV and up to 35% when the Fermi energy is 100 meV.

Abstract-Bessel-like beam generated by an axicon based on parallel-plate waveguides

Tingting Shen, Tingting Lang, Mengru Wu, and Zhanghua Han

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-57-21-6174

The axicon is the simplest and most effective optical element for generating the zero-order Bessel-like beam. The zero-order Bessel-like beam, which has the characteristics of small spot size, high brightness, good direction, and large collimation distance, can be applied to optical micromanipulation and power transmission. In this paper, we proposed and designed a structure for phase manipulation based on parallel-plate waveguides that can be used to realize the functionality of the axicon in the terahertz (THz) region. Meanwhile, we characterized the influence of the cone angle of the axicon and the waist radius of the incident Gaussian beam on the generated zero-order Bessel-like beam by simulation. The planar structure, consisting of a parallel stack of thin copper plates, can be easily fabricated to fulfill the phase requirement to realize the zero-order Bessel-like beam and also can be utilized in THz imaging systems, THz sensing systems, THz communication systems, etc.

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