Abstract-Scattering of spoof surface plasmon polaritons in defect-rich THz waveguides

Andreas K. Klein, Alastair Basden, Jonathan Hammler, Luke Tyas, Michael Cooke, Claudio Balocco, Dagou Zeze, John M. Girkin, Andrew Gallant

https://www.nature.com/articles/s41598-019-42412-6

We report on the first observation of ‘Spoof’ Surface Plasmon Polariton (SPP) scattering from surface defects on metal-coated 3D printed, corrugated THz waveguiding surfaces. Surface defects, a result of the printing process, are shown to assist the direct coupling of the incident free-space radiation into a spoof SPP wave; removing the need to bridge the photon momentum gap using knife-edge or prism coupling. The free space characteristics, propagation losses and confinement of the spoof SPPs to the surface are measured, and the results are compared to finite-difference time domain simulations. Angular resolved THz spectroscopy measurements reveal the scattering patterns from surfaces and are compared with Mie theory, taking into account the shortened wavelength of the photons in their bound SPP state compared to their free space wavelength. These results confirm yet another similarity between the properties of THz spoof SPPs and their natural, non-spoof, counterparts at optical and infrared frequencies which also, unexpectedly, adds functionality to the structures.

Abstract-Field imaging near to the surface of terahertz reflective optics using a vector network analyzer

Maryam Hajji, Jonathan Hammler, Dagou Zeze, Claudio Balocco, and Andrew J. Gallant

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-56-31-8746

A vector network analyzer-based quasi-optical measurement system that is suitable for mapping electric field intensity and phase near to the surface of terahertz reflective optics is presented. The system uses a fixed five parabolic mirror and transmitter/receiver head arrangement that has the benefit of requiring only the sample to be swept during measurement. The system has been tested with a micromilled aluminum zone plate reflector used as an exemplar structure. The measured focal point of the zone plate reflector, at its designed frequency of 1 THz, is shown to correspond well to both finite difference time-domain simulations and analytical theory.

© 2017 Optical Society of America

Measure Permittivity at Terahertz Frequencies

Jack Browne | Microwaves and RF
http://mwrf.com/test-measurement-analyzers/measure-permittivity-terahertz-frequencies

Terahertz frequencies hold great promise for short-range communications, radar, and medical applications, provided that more can be learned about the building blocks of circuits (such as substrate materials) at those high frequencies. To that end, Jonathan Hammler, Andrew J. Gallant, and Claudio Balocco of the U.K.-based School of Engineering and Computing Sciences at Durham University developed a simple system based on a vector network analyzer (VNA) for the noncontact, free-space measurement of the permittivity (dielectric constant) of materials within the 750- to 1,100-GHz frequency range.

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The system can be applied to the high-throughput quality-control measurements of materials used to fabricate components—such as lenses, diffractive optics, filters, and waveguide—typically employed in terahertz applications. Main components of the measurement system include a commercial VNA and Schottky-diode-based frequency converters.

The measurement system relies on a minimum of additional components, with two parabolic mirrors and a sample holder that must be aligned with a pair of horn antennas for material measurements. System drift is minimized due to the short optical path and lack of moving components. In addition, the researchers developed a fast and easy-to-use numerical calibration method for the system.

Measurements are analyzed with the aid of the MATLAB commercial analysis software from MathWorks running on a PC to provide nonlinear optimization algorithms. Several silicon and gallium-arsenide (GaAs) wafers measurements were made, with only minimal variations around mean permittivity values for each material.

See “Free-Space Permittivity Measurement at Terahertz Frequencies With a Vector Network Analyzer,” IEEE Transactions on Terahertz Science and Technology, Vol. 6, No. 6, November 2016, p. 817.