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Tunable terahertz all-dielectric linear-to-circular polarization conversion metasurface

Ju Xiacao, Wang Weiguang, Liu Bingchao, Hou Yanzhao, Wen Huashun, Yang Daquan

Optica Applicata

2022

Vol. 52, nr 4

551--563

Terahertz (THz) linear-to-circular (LTC) polarization conversion plays a crucial role in imaging and 6G wireless communication. This paper will give an account of a thermally tunable THz LTC polarization converter by using the active all-dielectric metasurface. It consists of zirconium oxide (ZrO2) microsphere resonators, active strontium titanate (STO) cladding, and flexible polyimide substrate. Through numerical simulation, the amplitude of the ellipticity of the proposed polarization converter at 0.265 THz is –1, indicating that perfect right-hand circular polarization (RHCP) wave is achieved. Meanwhile, the amplitude of the ellipticity is less than –0.8 between 0.247 and 0.278 THz (relative bandwidth is 12%). In addition, with the temperature changes of 180 K (from 200 to 380 K), the operating frequency of the converter can be tuned from 0.220 to 0.291 THz, a sensitivity about 39 GHz/100 K is achieved. Besides, the modulation depth of the ellipticity amplitude can achieve 92% at 0.220 THz, which demonstrates that the converter can output terahertz wave with different polarization states, and the device can be fabricated on a large scale. These perfect conversion performances show that the converter has potential applications in high-speed communication and imaging.

The Microwave Sources for EPR Spectroscopy

Hruszowiec M., Nowak K., Szlachetko B., Grzelczak M., Czarczyński W., Pliński E. F., Więckowski T.

Journal of Telecommunications and Information Technology

2017

nr 2

18--25

Rapid development of many scientific and technical disciplines, especially in material science and material engineering increases a demand for quick, accurate and cheap techniques of materials investigations. The EPR spectroscopy meets these requirements and it is used in many fields of science including biology, chemistry and physics. For proper work, the EPR spectrometer needs a microwave source, which are reviewed in this paper. Vacuum tubes as well as semiconductor generators are presented such as magnetron, klystron, traveling wave tube, backward wave oscillator, orotron, gyrotron, Gunn and IMPATT diodes. In this paper main advantages of gyrotron usage, such as stability and an increased spectral resolution in application to EPR spectroscopy is discussed. The most promising and reliable microwave source is suggested.

Generacja fal terahercowych z zastosowaniem laserów półprzewodnikowych

Mroziewicz B.

Elektronika : konstrukcje, technologie, zastosowania

2009

Vol. 50, nr 9

132-143

Pasmo częstotliwości terahercowych w widmie promieniowania elektromagnetycznego to ostatni skrawek tego widma dotychczas słabo wykorzystywany w technice. Powodem tego stanu rzeczy są trudności w osiągnięciu fal o częstotliwości terahercowej. Tymczasem technika ta znajduje coraz szersze możliwości aplikacyjne. W artykule omówiono metody generacji fal terahercowych oparte na wykorzystaniu promieniowania emitowanego przez lasery - szczególnie lasery półprzewodnikowe. Znaczną część artykułu poświęcono opisowi zjawisk leżących u podstaw tej techniki z położeniem nacisku na zjawisko mieszania częstotliwości. Szczególną uwagę zwrócono na potencjał tkwiący w kwantowych laserach kaskadowych i laserach dwufalowych, które uważane są za szczególnie perspektywiczne z punktu widzenia budowy generatorów promieniowania terahercowego o znaczącej mocy wyjściowej.

The terahertz frequency band is the last shred of the electromagnetic radiation spectrum that had been left al most unused in practical applications. The situation has been caused by difficulties encountered when trying to generate terahertz wavelengths of meaningful power. However, this technique finds ever increasing applications and has aroused a great interest in its development. In the paper we describe basic phenomena leading to generation of terahertz signals by optical methods. Photo-mixing of laser beams is treated more in detail due to variety of possibilities offered by the method itself and semiconductor lasers in particular. Quantum Cascade Lasers and two-colour external cavity lasers deserve special attention as promising sources of high output power terahertz signals and the state of the art in this field has been therefore enlightened more thoroughly.