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1

Bandpass THz frequency selective surface with flat passband

Hussein Muaad, Alrudainy Haider, Abdulkawi Wazie M.

Przegląd Elektrotechniczny

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2022

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R. 98, nr 8

73--76

EN

The thickness of the substrate turns out to be approximately a quarter of a wavelength in implementing second-order passband frequency selective surfaces (FSSs) to achieve better response with faster roll-off and smooth in-band frequency response. The problem with using a thicker substrate in FSS structures is that the losses will be high, especially in millimeter and terahertz (THz) frequency applications. For that, a new approach is introduced in this paper to deal with this issue. The approach is to adopt an improvement of the coupling coefficient without increasing the thickness of the substrate. Based on this, a thin band-pass filter (FSS) with low losses and flat-top response is built. An equivalent circuit model has been provided to characterize the structure based on electric and magnetic fields distributions. Thus, it is proven in this paper that the calculated results are in good agreement with the numerical simulation results.

PL

Okazuje się, że grubość podłoża wynosi około jednej czwartej długości fali w implementacji powierzchni selektywnych częstotliwościowo pasma przepustowego (FSS) drugiego rzędu, aby uzyskać lepszą odpowiedź z szybszym wycofywaniem się i gładką odpowiedzią częstotliwościową w paśmie. Problem z użyciem grubszego podłoża w strukturach FSS polega na tym, że straty będą wysokie, szczególnie w zastosowaniach o częstotliwościach milimetrowych i terahercowych (THz). W tym celu w niniejszym opracowaniu wprowadzono nowe podejście do rozwiązania tego problemu. Podejście polega na przyjęciu poprawy współczynnika sprzężenia bez zwiększania grubości podłoża. Na tej podstawie budowany jest cienki filtr pasmowoprzepustowy (FSS) o niskich stratach i płaskiej odpowiedzi. Dostarczono równoważny model obwodu w celu scharakteryzowania struktury w oparciu o rozkłady pól elektrycznych i magnetycznych. Tym samym dowiedziono w niniejszej pracy, że obliczone wyniki są w dobrej zgodności z wynikami symulacji numerycznej.

2

Fotonika i Technologie terahercowe

Romaniuk R. S.

Elektronika : konstrukcje, technologie, zastosowania

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2011

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Vol. 52, nr 11

133-137

PL

Artykuł omawia podstawowe cechy terahercowego pasma częstotliwości. Przedstawiono podstawowe charakterystyki układu terahercowego złożonego ze źródła promieniowania, ośrodków i linii transmisyjnych, układów przetwarzania sygnałów oraz detektorów. Taki układ znajduje zastosowania badawcze, a także praktyczne w dwóch obszarach: obrazowanie terahercowe transmisyjne i odbiciowe oraz radar terahercowy bliskiego zasięgu a także systemy czujnikowe w paśmie THz. W kraju uruchomiono ostatnio kilka projektów badawczych dotyczących źródeł i detektorów promieniowania THz oraz ich zastosowań, w tym duży projekt infrastrukturalny, inwestycyjny FOTEH na PW. Omówiono program projektu FOTEH w obszarze technologii terahercowych i potencjalne konsekwencje jego realizacji w kraju.

EN

The paper debates basic features of the terahertz band of frequencies. There are presented fundamental characteristics of the basic terahertz system consisting of a THz source, propagation media, transmission lines, THz signal processing, and detectors. Such a system finds research application, but also practical in two main areas: terahertz imaging - transmissive and reflective, and as close range THz radar, but also as sensory systems mainly for molecular sensing. There were launched in this country a few THz research projects concerning the THz sources, detectors and their applications. Among these projects there is an infrastructural one called FOTEH, opened at WUT. The details of this project are debated and the consequences of its realization in this country.

3

THz/sub-THz bolometer based on electron heating in a semiconductor waveguide

Dobrovolsky V., Sizov F.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

250-258

EN

Direct detection THz/sub-THz bolometer is proposed. In it an electromagnetic wave propagates in the bipolar semiconductor waveguide, heats electrons and holes there, and therefore creates their bipolar thermodiffusion flow and, as well as, the electromotive force (emf). The flow causes the carrier excess concentration. Both this concentration and emf are used to get the bolometer response voltage. The bolometer theoretical model is developed. The possibility without cooling or moderate cooling (about 100 K for the Cd₀.₂Hg₀.₈Te bolometers) to get acceptable for applications values of the noise equivalent power is shown. Experimental results confirm the main model conclusions.

4

Free Electron Laser in Poland

Romaniuk R. S.

Electronics and Telecommunications Quarterly

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2009

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Vol. 55, No 4

669-682

EN

The idea of building a new IVth generation of light sources of high luminosity, which use accelerators, arose in the 80ties of XXth century. Now, in a numerable synchrotron and laser laboratories in Europe, an intense applied research on free electron lasers has been carried out for a couple of years (FEL) [17,18]. Similarly, in this country, free electron laser in Poland - POLFEL [9] is in a design, a coherent light source of the IVth generation, characterized by very short pulses in the range of 10-100fs, of big power 0,2GW and UV wavelength of 27nm, of average power 1W, with effective high power third harmonic of 9nm. The laser consists of a linear superconducting accelerator 100m in length, undulator and experimental lines. It generates a monochromatic and coherent radiation and can be tuned from THz range via IR, visible to UV, and potentially to X-rays. The linac works in quasi-CW or real-CW mode. It is planned by IPJ [9,10] and XFEL-Poland Consortium [16] as a part of the ESFRI [1] priority Euro FEL infrastructure collaboration network [6], part of the European Research Area - ERA [2]. The paper discusses: FEL background in Poland as a part of EuroFEL infrastructure, FEL parameters and performance, FEL research and technical program and FEL networking in Europe and worldwide. Emphasis is put on the usage of superconducting RF TESLA technology and ties linking Polfel and the European X-Ray Free Electron Laser. The Polfel team of researchers is now dissipated worldwide among such projects as Flash and E-xfel in Desy, Cebaf in JLab, Alba in Barcelona, Elettra in Trieste, ILC in Fermilb, LCLS in SLAC. Polfel creates an unique, but quite transient chance to gather and solidly accumulate for a long time this expertise in this country again.

5

Ambient temperature or moderately cooled semiconductor hot electron bolometer for mm and sub-mm regions

Dobrovolsky V. N., Sizov F. E., Kamenev Y. E., Smirnov A. B.

Opto-Electronics Review

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2008

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Vol. 16, No. 2

172-178

EN

A model of semiconductor hot electron bolometer (SHEB), in which electromagnetic radiation heats only electrons in narrow-gap semiconductor without its lattice slow-response heating, is considered. Free carrier heating changes the generation-recombination processes that are the reason of semiconductor resistance rise. It is estimated, that Hg₀.₈Cd₀.₂Te detector noise equivalent power (NEP) for mm and sub-mm radiation wavelength range can reach NEP ~ 10⁻¹¹ W at Δf = 1 Hz signal gain frequency bandwidth. Measurements performed at electromagnetic wave frequencies v = 36, 39, 55, 75 GHz, and at 0.89 and 1.58 THz too, with non-optimized Hg₀.₈Cd₀.₂Te antenna-coupled bolometer prototype confirmed the basic concept of SHEB. The experimental sensitivity Sv ~ 2 V/W at T = 300 K and the calculated both Johnson-Nyquist and generation-recombination noise values gave estimation of SHEB NEP ~ 3.5 × 10⁻¹⁰ W at the band-width Δf = 1 Hz and v = 36 GHz.