Terahertz Bandpass Filter Based on Frequency Selective Surface

Li, Jiu-Sheng, Yang Li, and Le Zhang. "Terahertz Bandpass Filter Based on Frequency Selective Surface." IEEE Photonics Technology Letters 30, no. 3 (2018): 238-241.

Abstract:

We designed a terahertz bandpass filter based on double-layer frequency selective surface. Details of the proposed terahertz wave filter design and of the related parametric analysis are presented and discussed. The proposed terahertz filter was fabricated by laser technology. The transmission spectrum was characterized by terahertz time-domain spectroscopy. The results show that the center frequency of the terahertz filter is about 1 THz with 3-dB bandwidth of 400 GHz.

for full paper see http://ieeexplore.ieee.org/document/8194866/

for more information about TeraView is https://www.azom.com/article.aspx?ArticleID=14796

Plasmonic Nanodisk Thin-Film Terahertz Photoconductive Antenna

Burford, Nathan M., Michael J. Evans, and Magda O. El-Shenawee. "Plasmonic Nanodisk Thin-Film Terahertz Photoconductive Antenna." IEEE Transactions on Terahertz Science and Technology (2017).

Abstract:

This paper presents the design, fabrication, and measurement of a plasmonic thin-film terahertz photoconductive antenna. Conventional terahertz photoconductive antennas suffer from poor optical-to-terahertz conversion efficiency, often on the order of 10−4. This is due to the low quantum efficiency of the device. The goal of this work is to demonstrate enhanced terahertz emission from a plasmonic thin-film device architecture. The combination of plasmonic nanodisks, a 120-nm low-temperature-grown gallium arsenide thin-film, and a bottom-located bowtie antenna has demonstrated the feasibility of producing such devices. Fabrication attempts and failure analysis is discussed in this work. Experimental characterization measuring the peak-to-peak electric field values of the terahertz pulses emitted from the device prototypes showed approximately five times improvement in plasmonic thin-film devices compared to conventional devices. The plasmonic thin-film devices had a measureable terahertz bandwidth of ∼5 THz. This indicates that the plasmonic thin-film architecture has a potential for producing high optical-to-terahertz conversion efficiencies across a wide frequency range.

for full paper see http://ieeexplore.ieee.org/abstract/document/8239849/

for more information about TeraView is https://www.azom.com/article.aspx?ArticleID=14796

Resolving the rapid water absorption of porous functionalised calcium carbonate powder compacts by terahertz pulsed imaging

Markl, Daniel, Parry Wang, Cathy Ridgway, Anssi-Pekka Karttunen, Prince Bawuah, Jarkko Ketolainen, Patrick Gane, Kai-Erik Peiponen, and J. Axel Zeitler. "Resolving the Rapid Water Absorption of Porous Functionalised Calcium Carbonate Powder Compacts by Terahertz Pulsed Imaging." Chemical Engineering Research and Design (2018).

Abstract

Cost effectiveness, ease of use and patient compliance make pharmaceutical tablets the most popular and widespread form to administer a drug to a patient. Tablets typically consist of an active pharmaceutical ingredient and a selection from various excipients. A novel highly porous excipient, functionalised calcium carbonate (FCC), was designed to facilitate rapid liquid uptake leading to disintegration times of FCC based tablets in the matter of seconds. Five sets of FCC tablets with a target porosity of 45–65% in 5% steps were prepared and characterised using terahertz pulsed imaging (TPI). The high acquisition rate (15 Hz) of TPI enabled the analysis of the rapid liquid imbibition of water into these powder compacts. The penetration depth determined from the TPI measurements as a function of time was analysed by the power law and modelled for both the inertial (initial phase) and Lucas-Washburn (LW, longer time Laplace-​Poiseuillian) regimes. The analysis of the hydraulic radius estimated by fitting the liquid imbibition data to the LW equation demonstrates the impact of the porosity as well as the tortuosity of the pore channels on the liquid uptake performance. The tortuosity was related to the porosity by a geometrical model, which shows that the powder compact is constructed by aggregated particles with low permeability and its principal axis perpendicular to the compaction direction. The consideration of the tortuosity yielded a very high correlation (R2 = 0.96) between the porosity and the hydraulic pore radius. The terahertz data also resolved fluctuations (0.9–1.3 Hz) of the liquid movement which become more pronounced and higher in frequency with increasing porosity, which is attributed to the constrictivity of pore channels. This study highlights the strong impact of a tablet's microstructure on its liquid penetration kinetics and thus on its disintegration behaviour.

for full paper see https://www.sciencedirect.com/science/article/pii/S0263876218300017

for more information about TeraView is https://www.azom.com/article.aspx?ArticleID=14796

Damage assessment in composite materials using full wavefield analysis

WANDOWSKI, Tomasz, Pawel H. MALINOWSKI, and Wieslaw M. OSTACHOWICZ. "Damage assessment in composite materials using full wavefield analysis." see http://www.ndt.net/article/aero2017/papers/NDT2017-014_Damage_assessment_in_composite_materials_using_full_wavefield_analysis.pdf

Abstract 

In this paper damage assessment method is presented. This method is based on phenomenon of guided elastic waves propagation. Guided waves are generated by piezoelectric transducer and registered by Scanning Laser Doppler Vibrometer (SLDV). Signal processing is based on the analysis of full wave-field measurements. In this approach guided wave signals are gathered from dense mesh of measurement points spanned over investigated area of investigated structure. This approach allows to create animations representing the guided wave propagation which are suitable for analysis of interaction of guided waves with different discontinuities located in composite material. In the research attention is especially focused on analysis of phenomenon of guided wave mode conversion. This phenomenon occurs due to the interaction of guided wave with discontinuities in the structure. Guided wave mode conversion phenomenon has potential for damage detection. Method is validated for the fibre reinforced composite materials. In the research such discontinuities like delamination simulated by teflon insert with different shapes and location as well as true delamination created by impact are investigated. In the research auxiliary nondestructive testing (NDT) method is utilized. The aim of this method is to indicate the depth of discontinuity, and to prove that delamination was created. Auxiliary method is based on terahertz spectroscopy (THz). This method is based on analysis of propagation of electromagnetic waves in the terahertz band. THz spectroscopy method can be utilized for damage assessment in the materials that do not conduct electric current. 

for more information about TeraView is https://www.azom.com/article.aspx?ArticleID=14796

Thermally induced tunability of a terahertz metamaterial by using a specially designed nematic liquid crystal mixture

Kowerdziej, Rafał, Marek Olifierczuk, and Janusz Parka. "Thermally induced tunability of a terahertz metamaterial by using a specially designed nematic liquid crystal mixture." Optics Express 26, no. 3 (2018): 2443-2452.

Abstract

The search for new low loss nematic liquid crystal mixtures with enhanced birefringence and low temperature of nematic-to-isotropic phase transition plays a pivotal role in a development of new applications in the emerging field of thermally tunable metamaterials. Here we maximize thermally induced tunability of a terahertz metamaterial by using a specially designed nematic liquid crystal mixture. It is shown that the resonant response of a metamaterial device can be effectively tuned both in terms of its magnitude and wavelength with the spectral tunability approaching the theoretical limit of 8 GHz. Electromagnetic simulations confirm our tests and match the experimental observations well. The suggested approach opens new routes for next-generation soft-matter-based filtering and sensing components and devices.

"of the metamaterial when loaded with a nematic liquid crystal mixture during the heating process, THz-TDS (TeraView TPS 3000 …" 

for full paper see https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-3-2443

for more information about TeraView is https://www.azom.com/article.aspx?ArticleID=14796