| 1. |
- Campion, James, 1989-, et al.
(författare)
-
Ultra‐Wideband Integrated Graphene‐Based Absorbers for Terahertz Waveguide Systems
- 2022
-
Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X. ; 8:9, s. 2200106-2200106
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents novel graphene-based absorber materials which can be directly integrated in terahertz waveguide systems. A simple, low-cost integration method is developed, allowing graphene augmented inorganic nanofibers to be embedded inside a metallic waveguide. In contrast to existing absorbers, the ability to embed such materials in a metallic waveguide allows them to be integrated into complete terahertz systems for large-scale applications. The electromagnetic properties of such materials are then examined using standard network analysis techniques. A wideband measurement setup is developed to enable measurement of a single sample from 67 to 500 GHz, eliminating the need to fabricate multiple samples. The porosity of the integrated material leads to excellent electromagnetic performance across a wide range of frequencies. The samples are found to have a reflection coefficient less than −10 dB for frequencies above200 GHz, while their attenuation per unit length exceeds 35 dB mm−1. The low reflectivity of the material allows it to be used in systems applications where undesired reflections must be avoided. The electromagnetic shielding effectiveness of the material is assessed, with a total effectiveness of 20–45 dB observed for 0.84 mm thick samples.
|
|
| 2. |
|
|
| 3. |
- Drozdz, Piotr A., et al.
(författare)
-
Highly efficient absorption of THz radiation using waveguide-integrated carbon nanotube/cellulose aerogels
- 2022
-
Ingår i: APPLIED MATERIALS TODAY. - : Elsevier BV. - 2352-9407. ; 29
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents the preparation, compositional and electromagnetic characterization of modified few-walled carbon nanotubes/nanofibrillar cellulose (FWCNT/NFC) aerogels integrated in a standard terahertz hollow waveguide and studies their operation as absorbers of electromagnetic waves in the WR-3.4 band (220-330 GHz). Hybrid aerogels consisting of different weight ratios of NFC and modified FWCNT are prepared by freezedrying and characterized through scanning electron microscopy and Raman spectroscopy, and then placed within waveguide cassettes in a simple, low-cost and efficient way that requires no special equipment. A broadband measurement setup is employed for examining the electromagnetic response of the materials. It is found that the materials are excellent absorbers with an average shielding efficiency of 66 dB in the best case and return loss above 10 dB across the band with a flat frequency response. FWCNT aerogels are assessed as a promising candidate for terahertz waveguide terminations.
|
|
| 4. |
- Drozdz, Piotr A., et al.
(författare)
-
Integrated CNT Aerogel Absorbers for Sub-THz Waveguide Systems
- 2022
-
Ingår i: 2022 IEEE/MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM (IMS 2022). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 906-909
-
Konferensbidrag (refereegranskat)abstract
- The ongoing development of sub-THz systems and applications has created a need for new absorbing materials which can be integrated in a simple, low-cost manner. Here, we investigate the properties of CNT-based aerogels in the range of 67-110 GHz and develop a simple technique for their integration. The aerogels are synthesised using standard techniques and then shaped using a laser cutter to allow for direct integration. The S-parameters of a total of four aerogel absorber samples are measured. The absorbers offer a return loss of up to 12 - 14.5 dB across the measurement band, with a maximum absorption 2.54 of 5 dB/mm The observed performance makes CNT aerogels extremely promising candidates for use in sub-THz waveguide systems and applications.
|
|
| 5. |
- Lyubchenko, Dmitri, et al.
(författare)
-
Millimeter Wave Beam Steering Based on Optically Controlled Carbon Nanotube Layers
- 2018
-
Konferensbidrag (refereegranskat)abstract
- In this paper, the dielectric constant changing of thin carbon nanotube layers under light illumination was used for phase shifter development in dielectric rod waveguides. This designed phase shifter was introduced to the dielectric rod waveguide dual-antenna array. The measurements of the beam steering at 90 GHz of the dielectric rod antenna array, covered with carbon nanotubes, were carried out.
|
|
| 6. |
- Morales, Alvaro, et al.
(författare)
-
Photonic-Based Beamforming System for Sub-THz Wireless Communications
- 2019
-
Konferensbidrag (refereegranskat)abstract
- This work presents a sub-THz transmitter scheme for wireless communications with beam steering capabilities based on photonics means. A true time delay 1x4 beamforming photonic chip is designed in Si3N4 technology to continuously tune the progressive time delay between consecutive antenna elements. Simulation results show a progressive delay up to 15 ps with a bandwidth of 1.3 GHz, enabling broadband operation at frequencies above 75 GHz. The sub-THz signals are generated on photoconductive antennas on chip by photonic heterodyning. The design of a dielectric rod antenna array is also presented to efficiently radiate the generated wave.
|
|
| 7. |
|
|
| 8. |
- Przewłoka, Aleksandra, et al.
(författare)
-
Characterization of Silver Nanowire Layers in the Terahertz Frequency Range
- 2021
-
Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 14:23, s. 7399-
-
Tidskriftsartikel (refereegranskat)abstract
- Thin layers of silver nanowires are commonly studied for transparent electronics. However, reports of their terahertz (THz) properties are scarce. Here, we present the electrical and optical properties of thin silver nanowire layers with increasing densities at THz frequencies. We demonstrate that the absorbance, transmittance and reflectance of the metal nanowire layers in the frequency range of 0.2 THz to 1.3 THz is non-monotonic and depends on the nanowire dimensions and filling factor. We also present and validate a theoretical approach describing well the experimental results and allowing the fitting of the THz response of the nanowire layers by a Drude–Smith model of conductivity. Our results pave the way toward the application of silver nanowires as a prospective material for transparent and conductive coatings, and printable antennas operating in the terahertz range—significant for future wireless communication devices.
|
|
| 9. |
- Przewloka, Aleksanda, et al.
(författare)
-
Conductivity inversion of methyl viologen-modified random networks of single-walled carbon nanotubes
- 2023
-
Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 202, s. 214-220
-
Tidskriftsartikel (refereegranskat)abstract
- One of the challenges of using carbon nanotubes electronics is achieving precise control of the conductivity type. It is particularly difficult to obtain the n-type conductive nanotubes. One of the most common methods of CNTs modification allowing to change their conductivity type is chemical functionalization. This paper describes the results of studies on non-covalent modification of randomly oriented single-walled carbon nan-otubes (SWCNT) layers with methyl viologen (MV), which allows for the change of the conductivity of SWCNT from p- to n-type. The properties of pristine and MV-modified SWCNT have been compared using Scanning Electron Microscopy, Raman spectroscopy, and X-ray Photoelectron Spectroscopy. The SWCNT conductivity type change was confirmed by photo-conductance under ultraviolet illumination and measurements in the field effect transistor configuration.
|
|
| 10. |
- Przewłoka, Aleksandra, et al.
(författare)
-
Single-walled carbon nanotube phase shifters for low THz frequencies
- 2021
-
Ingår i: The 11th International Conference on Metamaterials, Photonic Crystals and Plasmonics, META 2021. - : META Conference. ; , s. 1058-1059
-
Konferensbidrag (refereegranskat)abstract
- In this work single-walled carbon nanotube length dependence on phase tuning properties of dielectric rod waveguide is experimentally studied in ultra-wide frequency band of 0.1-0.5 THz.
|
|
