Abstract-A Broadband Polarization-Rotating Vivaldi Antenna for Beam Focusing of Terahertz Quantum Cascade Lasers

U. Senica, E. Mavrona, T. Olariu, A. Forrer, M. Beck, J. Faist, and G. Scalari

https://www.osapublishing.org/abstract.cfm?uri=CLEO_Europe-2019-cc_2_4

Terahertz (THz) Quantum Cascade Lasers (QCLs) have been of large interest in the context of very broadband and compact frequency combs in the THz spectral range. For THz QCLs, the double metal waveguide proved to be advantageous in terms of bandwidth, compactness and low dispersion. However, as it confines the optical mode to deeply subwavelength dimensions, the output beam is highly divergent. Previous solutions addressing this issue were either impractical or not so broadband. To improve the far-field properties of the double metal waveguide across a very large frequency range, we designed, fabricated and characterized a broadband, narrow beam Vivaldi Antenna .

© 2019 IEEE

Abstract-Terahertz properties of liquid crystals doped with ferroelectric BaTiO3 nanoparticles

U. Chodorow, E. Mavrona 
 N. Palka, O. Strzezysz, K. Garbat, S. Saitzek, J. F. Blach, V. Apostolopoulos, M. Kaczmarek & J. Parka

http://www.tandfonline.com/doi/abs/10.1080/02678292.2016.1271468?journalCode=tlct20

In this paper, we present the results of the terahertz measurements of liquid crystal (LC) ferroelectric BaTiO3nanoparticles (nps) suspensions in the range of frequency from 0.3 up to 3.0 THz. Two different sol-gel methods and the harvesting technique were used to fabricate the nanoparticles. Five LC materials served as hosts for the suspensions: two single compounds: 6CHBT and 2,3′,5′-trifluoro-4-(4-pentylcyclohexyl)-4′-(trifluoromethoxy)-1,1′-biphenyl, and three mixtures: 1867, 2037 and 2020. We characterise, for the first time, the refractive indices and absorption parameters of suspensions with harvested nps in the terahertz range and show how the process of the nps’ preparation affects their response. We observed the increase of birefringence for few LC suspensions in comparison with the pure LCs. The highest increase of birefringence was for 2020 suspension with one kind of ferroelectric nps. On the other hand in most cases the addition of ferroelectric nps to LC causes the increase of its absorption in the THz range. The measurements of LCs terahertz properties by using time-pulsed spectrometer were performed.

Abstract-Refractive indices and birefringence of hybrid liquid crystal - nanoparticles composite materials in the terahertz region

E. Mavrona^1,2,a), U. Chodorow³, M. E. Barnes¹, J. Parka^3,4, N. Palka⁵, S. Saitzek², J.-F. Blach², V. Apostolopoulos¹ and M. Kaczmarek¹
 HIDE AFFILIATIONS
1 School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, United Kingdom
2 CNRS UMR 8181, Unité de Catalyse et de Chimie du Solide - UCCS, UArtois, Faculté des Sciences Jean Perrin, SP18, F-62307 Lens Cedex, France
3 Institute of Applied Physics, Military University of Technology, Warsaw, Poland
4 Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Warsaw, Poland
5 Institute of Optoelectronics, Military University of Technology, Warsaw, Poland
a) Electronic mail: em3e12@soton.ac.uk
AIP Advances 5, 077143 (2015); http://dx.doi.org/10.1063/1.4927392

http://scitation.aip.org/content/aip/journal/adva/5/7/10.1063/1.4927392

We show that a hybrid LC-ferroelectric nanoparticle suspension of liquid crystal E7 doped with BaTiO3 nanoparticles leads to 10% increase in birefringence in the THz region of spectrum as compared to pure E7. Doped liquid crystals can be used to increase performance of THz modulators and waveplates. BaTiO3 nanoparticles used in the mixture were synthesised with the sol gel technique, and their refractive index has been measured in THz in powder form and in solution.