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Research into THz hyperspectral imaging is moving forward in the H-cube project

Researchers from the Department of Physics and Mathematics at the University of Eastern Finland are involved in the international H-cube project, which aims at developing a ready-for-the-market, room temperature hyperspectral camera for Terahertz radiation, capable of detecting the range from 100 GHz to 10 THz. The project constitutes part of the ATTRACT phase-2 research initiative funded by the European Union’s Horizon 2020 research and innovation programme.  

The development of the hyperspectral THz camera is based on converting the energy of THz radiation into heat, which changes the frequency of mechanical oscillations of the membrane. Silicon nitride has mechanical properties ideal for trampoline membranes but is transparent to THz radiation.

UEF’s role in the project pertains especially to the design and fabrication of special coatings that are needed for converting the energy of THz radiation into heat.

“These coatings are very lightweight and chemically stable, and they have high conductivity. Uniform coating allows for broad-band absorption, while meta-surfaces based on these coating designed at UEF allow for resonant absorption of radiation at a certain frequency, thus enabling hyperspectral features of the created THz vision system,” Professor Polina Kuzhir says. 

The H-cube project brings together the expertise of Consorzio Nazionale per le Ricerche (CNR), Coordinator, Asteria Business Development, Elettra Sincrotrone Trieste, Fondazione Bruno Kessler (United Kingdom), the Research Center for Non-Destructive Testing, UAB TeraVil (Lithuania), the University of Eastern Finland, and the University of Salerno.  

For more information, please contact:

Professor Polina Kuzhir, tel. +358 50 5666624, polina.kuzhir@uef.fi

H-cube project https://www.h-cube.eu/

Maria Corojari working on the h-cube tasks.
In the photo: Maria Corojari working on the h-cube tasks.

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Chiral Metamaterials For THz Polarisation Control (CHARTIST)

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Although nature has provided us a rich palette of materials to engineer devices for control electromagnetic (EM) radiation, this palette is limited. However, the limitations imposed by conventional materials can be overcome because the required functionality can be achieved by assembling an assortment of sub-wavelength entities together. The artificial materials created by structuring on a sub-wavelength scale are called metamaterials. Metamaterials typically consist of two- or three-dimensional arrays of entities (meta-atoms) with subwavelength period and structural features. The freedom in designing of “artificial atoms” enables a delicate tuning of the optical properties using Mie-type resonances. Due to the sub-wavelength periodicity of meta-atoms array, EM properties of metamaterials can often be described in terms of the permittivity, permeability, refraction index, and other uniform-material parameters. Among them a special attention of the research community is currently attracted to the rotatory power, a quantitative measure of metamaterial’s ability to rotate the polarization azimuth of the incident EM wave. A non-zero rotatory power is a feature inherent in chiral metamaterials. The reason for the special attention in chiral media is two-fold. First, chiral media interact with the right- and left- circularly polarized waves differently, which makes chiral metamaterials a unique playground to access fundamental aspects of the light-matter interaction. Second reason is that chiral media can be employed for polarization control. However, a beauty of the chiral metamaterials is that their optical properties go beyond those of chiral crystals and liquids, e.g. they may be engineered to have negative refraction index for one of the circular polarizations. The main goal of the CHARTIST is to provide chiral metamaterials that pave the way towards THz components having unprecedented tunability and being beyond the state-of the art in terms of the THz radiation control. We will create arrays of meta-atoms, which are deposited on a dielectric or semiconducting substrate. The meta-atom will be designed to maximize THz response and to enable control of this response by intense laser pulses and external static electric fields. Unprecedented tunability will be based on the graphene membrane placed on the array of chiral meta-atoms deposited on the dielectric substrate. By adding a solid electrolyte layer on the top of the membrane we will tune the carrier densities by applying a small gate voltage thus achieving modulation of the polarization and amplitude of the transmitted THz wave. Such a geometry enables also combing the electrical and optical control of the carrier density providing a feasible approach for achieving THz polarization control. Coordinator: University of Eastern Finland (UEF) Participants: Foundation for Research and Technology – Hellas (FORTH), Greece Optoelectronic Research Centre of the University of Southampton (ORC), United Kingdom Centre National De La Recherche Scientifique(CNRS), France S.Ep. CommonsLab, Greece XpectralTEK LDA (XPEC), Portugal NAPA Technologies, France Partners: National University Corporation Theuniversity Of Tokyo (IPST), Japan  

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