Free-Space Subterahertz-Field Polarization Controlled by Selection of Waveguide Modes

Journal article (2021)

Authors

M.P. Westig QN/Klapwijk Lab , Kavli institute of nanoscience Delft
R. Thierschmann Kavli institute of nanoscience Delft, QN/Klapwijk Lab
A.J. Katan Kavli institute of nanoscience Delft, QN/Afdelingsbureau
M. Finkel Kavli institute of nanoscience Delft, QCD/DiCarlo Lab - QuTech Advanced Research Centre
T.M. Klapwijk Kavli institute of nanoscience Delft, QN/Afdelingsbureau
Research Group
QN/Afdelingsbureau
Copyright: © 2021 M.P. Westig, R. Thierschmann, A.J. Katan, M. Finkel, T.M. Klapwijk
DOI
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https://doi.org/10.1103/PhysRevApplied.16.024049
More Info
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Published Date

2021

Language

English

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Research Group

QN/Afdelingsbureau

Abstract

We experimentally study the free-space electromagnetic field emitted from a multimode rectangular waveguide equipped with a diagonal-horn antenna. Using the frequency range of 215-580 GHz, a photomixer is used to launch a free-space circularly polarized electromagnetic field, exciting multiple modes at the input of the rectangular waveguide via an input diagonal-horn antenna. A second photomixer is used, together with a silicon mirror Fresnel scatterer, to act as a polarization-sensitive coherent detector to characterize the emitted field. We find that the radiated field, excited by the fundamental waveguide mode, is characterized by a linear polarization. In addition, we find that the polarization of the radiated field rotates by 45 if selectively exciting higher-order modes in the waveguide. Despite the higher-order modes, the radiated field appears to maintain a predominant Gaussian beam character, since an unidirectional coupling to a detector was possible, whereas the unidirectionality is independent of the frequency. We discuss a possible application of this finding.