| 1. |
- Anoshkin, Ilya V., et al.
(författare)
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Freeze-Dried Carbon Nanotube Aerogels for High-Frequency Absorber Applications
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:23, s. 19806-19811
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Tidskriftsartikel (refereegranskat)abstract
- A novel technique for millimeter wave absorber material embedded in a metal waveguide is proposed. The absorber material is a highly porous carbon nanotube (CNT) aerogel prepared by a freeze-drying technique. CNT aerogel structures are shown to be good absorbers with a low reflection coefficient, less than -12 dB at 95 GHz. The reflection coefficient of the novel absorber is 3-4 times lower than that of commercial absorbers with identical geometry. Samples prepared by freeze-drying at -25 degrees C demonstrate resonance behavior, while those prepared at liquid nitrogen temperature (-196 degrees C) exhibit a significant decrease in reflection coefficient, with no resonant behavior. CNT absorbers of identical volume based on wet-phase drying preparation show significantly worse performance than the CNT aerogel absorbers prepared by freeze-drying. Treatment of the freeze-dried CNT aerogel with n- and p-dopants (monoethanolamine and iodine vapors, respectively) shows remarkable improvement in the performance of the waveguide embedded absorbers, reducing the reflection coefficient by 2 dB across the band.
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| 2. |
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| 3. |
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| 4. |
- Demchenko, P., et al.
(författare)
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Study of optical pumping influence on carbon nanotubes permittivity in THz frequency range
- 2018
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Ingår i: Journal of Physics. - : Institute of Physics Publishing.
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Konferensbidrag (refereegranskat)abstract
- Equivalent complex permittivity of carbon nanotubes (CNT) was measured with/without light illumination at the frequency range of 0.2-1 THz. It was shown that we can tune the dispersion of the CNT complex conductivity during varying of optical pumping (wavelength of 980 nm). These results mean that CNT is perspective candidate for development of THz tunable attenuators and phase shifters.
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| 5. |
- Gomon, D., et al.
(författare)
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Opticaly tunable conductivity of carbon nanotubes in terahertz frequency range
- 2018
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580460
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Konferensbidrag (refereegranskat)abstract
- Impact of infrared radiation illumination (980 nm) on the properties of carbon nanotubes (CNT), such as complex conductivity and permittivity, with different geometric parameters in the frequency range of 0.2-1.0 THz was studied.
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| 6. |
- Lyubchenko, Dmitri, et al.
(författare)
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Millimeter Wave Beam Steering Based on Optically Controlled Carbon Nanotube Layers
- 2018
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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.
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| 7. |
- Smirnov, Serguei, et al.
(författare)
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Carbon Nanotube Layer Modeling for Computer Simulation of Optically Controlled Phase Shifters
- 2018
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Konferensbidrag (refereegranskat)abstract
- We propose an approach for efficient modeling of thin carbon nanotube layers for full-wave device simulations without increasing the number of simulation mesh cells. A surface impedance, used in computer simulations, is calculated from the dielectric constant of the material. The dielectric constant is modeled by a Drude–Lorentz resonance, fitted to experimental results. The approach allowed to study the nanotube-induced losses and finite-size resonance effects in optically-controlled, dielectric rod waveguide-based phase shifters. The correctness of the model was verified both by the simulated and the measured S-parameters in the W-band.
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| 8. |
- Smirnov, Serguei, et al.
(författare)
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Millimeter Wave Phase Shifter Based on Optically Controlled Carbon Nanotube Layers
- 2018
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Konferensbidrag (refereegranskat)abstract
- Surfaces with tunable impedance are usually lossy at high frequencies, which limits the design of millimeter wave and Terahertz devices. This work experimentally demonstrates a phase shifter based on single-walled carbon nanotubes and dielectric rod waveguides in the 220–330 GHz frequency range. Thin carbon nanotube layers are used as a tunable impedance surface with the dielectric properties optically controlled by laser illumination.
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| 9. |
- Smirnov, Serguei, et al.
(författare)
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Optically controlled dielectric properties of single-walled carbon nanotubes for terahertz wave applications
- 2018
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 10:26, s. 12291-12296
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Tidskriftsartikel (refereegranskat)abstract
- Materials with tunable dielectric properties are valuable for a wide range of electronic devices, but are often lossy at terahertz frequencies. Here we experimentally report the tuning of the dielectric properties of single-walled carbon nanotubes under light illumination. The effect is demonstrated by measurements of impedance variations at low frequency as well as complex dielectric constant variations in the wide frequency range of 0.1-1 THz by time domain spectroscopy. We show that the dielectric constant is significantly modified for varying light intensities. The effect is also practically applied to phase shifters based on dielectric rod waveguides, loaded with carbon nanotube layers. The carbon nanotubes are used as tunable impedance surface controlled by light illumination, in the frequency range of 75-500 GHz. These results suggest that the effect of dielectric constant tuning with light, accompanied by low transmission losses of the carbon nanotube layer in such an ultra-wide band, may open up new directions for the design and fabrication of novel Terahertz and optoelectronic devices.
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