Articoli di riviste: "Twisted waveguides"

1

Briet, Philippe, Hynek Kovařík e Georgi Raikov. "Scattering in twisted waveguides". Journal of Functional Analysis 266, n. 1 (gennaio 2014): 1–35. http://dx.doi.org/10.1016/j.jfa.2013.09.026.

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Kovařík, Hynek, e Andrea Sacchetti. "Resonances in twisted quantum waveguides". Journal of Physics A: Mathematical and Theoretical 40, n. 29 (3 luglio 2007): 8371–84. http://dx.doi.org/10.1088/1751-8113/40/29/012.

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Shyroki, Dzmitry M. "Exact Equivalent Straight Waveguide Model for Bent and Twisted Waveguides". IEEE Transactions on Microwave Theory and Techniques 56, n. 2 (2008): 414–19. http://dx.doi.org/10.1109/tmtt.2007.914637.

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4

Wilson, J. L., Cheng Wang, A. E. Fathy e Y. W. Kang. "Analysis of Rapidly Twisted Hollow Waveguides". IEEE Transactions on Microwave Theory and Techniques 57, n. 1 (gennaio 2009): 130–39. http://dx.doi.org/10.1109/tmtt.2008.2009042.

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5

Ekholm, T., H. Kovařík e D. Krejčiřík. "A Hardy Inequality in Twisted Waveguides". Archive for Rational Mechanics and Analysis 188, n. 2 (5 febbraio 2008): 245–64. http://dx.doi.org/10.1007/s00205-007-0106-0.

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Briet, Philippe, Hiba Hammedi e David Krejčiřík. "Hardy Inequalities in Globally Twisted Waveguides". Letters in Mathematical Physics 105, n. 7 (6 giugno 2015): 939–58. http://dx.doi.org/10.1007/s11005-015-0768-8.

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7

Kirsch, Werner, David Krejčiřík e Georgi Raikov. "Lifshits Tails for Randomly Twisted Quantum Waveguides". Journal of Statistical Physics 171, n. 3 (21 marzo 2018): 383–99. http://dx.doi.org/10.1007/s10955-018-2001-5.

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Bruneau, Vincent, Pablo Miranda e Nicolas Popoff. "Resonances near thresholds in slightly twisted waveguides". Proceedings of the American Mathematical Society 146, n. 11 (23 luglio 2018): 4801–12. http://dx.doi.org/10.1090/proc/14141.

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9

Karpierz, M. A., K. A. Brzdąkiewicz e Q. V. Nguyen. "Modeling of Spatial Solitons in Twisted Nematics Waveguides". Acta Physica Polonica A 103, n. 2-3 (febbraio 2003): 169–75. http://dx.doi.org/10.12693/aphyspola.103.169.

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Karpierz, Mirosław, Marek Sierakowski e Tomasz Wolinski. "Light Beam Propagation in Twisted Nematics Nonlinear Waveguides". Molecular Crystals and Liquid Crystals 375 (2002): 313–20. http://dx.doi.org/10.1080/713738372.

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Nicolet, A., F. Zolla e S. Guenneau. "Modelling of twisted optical waveguides with edge elements". European Physical Journal Applied Physics 28, n. 2 (novembre 2004): 153–57. http://dx.doi.org/10.1051/epjap:2004189.

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12

Wilson, Joshua L., Aly E. Fathy, Yoon W. Kang e Cheng Wang. "Applications of Twisted Hollow Waveguides as Accelerating Structures". IEEE Transactions on Nuclear Science 56, n. 3 (giugno 2009): 1479–86. http://dx.doi.org/10.1109/tns.2009.2017534.

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13

KARPIERZ, MIROSłAW A., MAREK SIERAKOWSKI e TOMASZ R. WOLIńSKI. "Light Beam Propagation in Twisted Nematics Nonlinear Waveguides". Molecular Crystals and Liquid Crystals 375, n. 1 (1 gennaio 2002): 313–20. http://dx.doi.org/10.1080/10587250210548.

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Taira, Hisao. "Spin transfer of light waves in twisted optical waveguides". Journal of Physics B: Atomic, Molecular and Optical Physics 44, n. 19 (2 settembre 2011): 195401. http://dx.doi.org/10.1088/0953-4075/44/19/195401.

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Kudryshev, Sergey B., Valentin S. Minakov, Alexey A. Zakaluyzhnyy e Vladimir A. Peglivanyan. "Dynamics of transformation of ultrasonic vibrations in twisted waveguides". MATEC Web of Conferences 226 (2018): 04019. http://dx.doi.org/10.1051/matecconf/201822604019.

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The effective use of ultrasound energy in various technological processes largely depends on the type of ultrasonic vibrations. Wide application in practice has found longitudinal ultrasonic fluctuations in connection with simplicity of realization, and also presence of the developed theoretical and settlement base. The longitudinal-torsional ultrasonic oscillations, the realization of which practically does not differ from the realization of longitudinal oscillations, and the efficiency and technological flexibility are much higher than for longitudinal or torsional ultrasonic oscillations, practically no applications have been found. This is due to several circumstances and, above all, from the theoretical basis for the transformation of this type of oscillation, since the theory of compressedtwisted rods was developed mainly in connection with the problem of longitudinal stability. The article deals with the case of transformation of longitudinal ultrasonic oscillations into complex ones by attaching to the last stage of the concentrator of the longitudinal acoustic system of the twisted waveguide.

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Karpierz, M. A. "Nonlinear Properties of Waveguides with Twisted Nematic Liquid Crystal". Acta Physica Polonica A 99, n. 1 (gennaio 2001): 161–73. http://dx.doi.org/10.12693/aphyspola.99.161.

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17

Igarashi, H., e T. Honma. "A finite element analysis of TE modes in twisted waveguides". IEEE Transactions on Magnetics 27, n. 5 (settembre 1991): 4052–55. http://dx.doi.org/10.1109/20.104991.

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Baqir, Muhamad A., e Pankaj K. Choudhury. "On the Fast-Waves in Dispersive Core-Twisted Clad Waveguides". IEEE Antennas and Wireless Propagation Letters 15 (2016): 1735–38. http://dx.doi.org/10.1109/lawp.2016.2530812.

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Meyer, Andre, e Martin Schneider. "Robust design of a broadband dual-polarized transition from PCB to circular dielectric waveguide for mm-wave applications". International Journal of Microwave and Wireless Technologies 12, n. 7 (27 aprile 2020): 559–66. http://dx.doi.org/10.1017/s175907872000032x.

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A growing interest in dielectric waveguides (DWGs) as an alternative to commonly used waveguides (like coaxial or twisted-pair cables) for high data rate interconnects could be observed in the last few years. Especially in the mm-wave frequency range (30–300 GHz) applications with these waveguides benefit from low losses and low dispersion. Moreover, using both polarizations of the fundamental mode in such waveguides could theoretically double the data rate without the need of higher bandwidth or additional fibers. The connection between DWGs and commonly available transceiver chips requires broadband transitions from planar waveguides like microstrip lines to DWGs. In this paper, an overview of the current developments of such transitions is given and a novel low-complexity design is presented that reduces the space consumption by 35% related to recently published works. This allows an easy integration into a printed circuit board layout or a chip package. Furthermore, an extensive sensitivity analysis is presented to prove the robustness toward manufacturing tolerances. The transition is realized at W-band frequencies (75–110 GHz) and achieves a relative 10 dB-bandwidth of more than 25% with a minimum insertion loss of 1.2 dB. It is shown that these properties even hold for manufacturing tolerances of nowadays manufacturing processes.

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Timofeev, V. V., I. V. Trifanov e E. V. Patraev. "Mathematical modeling of the technological process of twisting a waveguide". Spacecrafts & Technologies 7, n. 4 (31 dicembre 2023): 251–58. http://dx.doi.org/10.26732/j.st.2023.4.03.

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Twisted waveguides are part of waveguide paths of antenna- feeder devices of spacecraft. They have high requirements for accuracy and reliability. They are made of profiled rectangular pipes. The twisting of waveguide pipes with a cross- sectional size of less than 11x5.5 mm is carried out in the device using a rigid calibration mandrel. The calculation method determined the main parameters of the technological process of twisting the waveguide tube (torque M, drawing force Pпр). When twisting workpieces with cross sections according to GOST, the torques (M) and drawing forces (Pпр) from the cross- section sizes vary according to a nonlinear relationship. Twisting the workpiece from M4 requires less torque (M) and drawing force (Pпр) than for the workpiece from M1. By mathematical modeling, it is possible to select the optimal technological mode in advance, thereby ensuring high quality of waveguide twisting manufacturing. To substantiate the calculation results, the methods of control of technological parameters and quality control of the product manufacturing were considered. A problem has been found in measuring the torque and pulling force when twisting the workpiece. Therefore, the pulling force should be measured from the machine. A method for measuring torque using a non- contact torque sensor is proposed. The manufacturing quality is supposed to be carried out by the STRESSVISION mechanical stress scanner, and electrical tests.

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Vavulin, D. N., e A. A. Sukhorukov. "Generation of orbital-angular-momentum entangled biphotons in twisted nonlinear waveguides". Journal of Physics: Conference Series 917 (novembre 2017): 062010. http://dx.doi.org/10.1088/1742-6596/917/6/062010.

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Knyazev, B. A., O. E. Kameshkov, A. K. Nikitin, V. S. Pavelyev e Yu Yu Choporova. "Feasibility of generating surface plasmon polaritons with a given orbital momentum on cylindrical waveguides using diffractive optical elements". Computer Optics 43, n. 6 (dicembre 2019): 992–1000. http://dx.doi.org/10.18287/2412-6179-2019-43-6-992-1000.

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Three optical systems employing diffractive optical elements to generate surface plasmon polaritons (SPP) with orbital angular momentum on axisymmetric conductors are considered. In all three systems, the incident radiation is first converted by binary spiral phase axicons into a set of plane waves converging to the optical axis. In the zone of intersection of these waves, a "twisted" Bessel beam is formed. By fitting the diameter of the first ring of the Bessel beam to the diameter of the cylindrical conductor, it is possible to generate a rotating SPP by the "end-fire coupling" method. The use of an additional lens makes it possible to convert the SPP-exciting Bessel beam into a vortex annular beam whose diameter is independent of the topological charge of the beam. In the third scheme, converging plane waves are “intercepted” by a cylindrical metal diffraction grating, which forms twisted SPPs on a cylindrical conductor connected to the grating. Examples of the possible use of the proposed systems in experiments on a terahertz free electron laser are presented.

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Oh, Min-Cheol, Wol-Yon Hwang e Kwangjoon Kim. "Transverse-electric/transverse-magnetic polarization converter using twisted optic–axis waveguides in poled polymers". Applied Physics Letters 70, n. 17 (28 aprile 1997): 2227–29. http://dx.doi.org/10.1063/1.118823.

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24

Xi-Sheng Fang e Zong-Qi Lin. "A Coupled-Mode Approach to the Analysis of Fields in Space-Curved and Twisted Waveguides". IEEE Transactions on Microwave Theory and Techniques 35, n. 11 (novembre 1987): 978–83. http://dx.doi.org/10.1109/tmtt.1987.1133795.

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25

Fujisawa, Takeshi, Takanori Sato e Kunimasa Saitoh. "Full-Vector Finite-Element Beam Propagation Method for Helicoidal Waveguides and Its Application to Twisted Photonic Crystal Fibers". Journal of Lightwave Technology 35, n. 14 (15 luglio 2017): 2894–901. http://dx.doi.org/10.1109/jlt.2017.2703889.

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Fujisawa, Takeshi, Takanori Sato e Kunimasa Saitoh. "Errata to “Full-Vector Finite-Element Beam Propagation Method for Helicoidal Waveguides and its Application to Twisted Photonic Crystal Fibers” [Jul 17 2894-2901]". Journal of Lightwave Technology 36, n. 18 (15 settembre 2018): 4211–12. http://dx.doi.org/10.1109/jlt.2018.2854881.

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27

Zhang, Feng, Ying Wang, Zhiyong Bai, Shen Liu, Cailing Fu, Yijian Huang, Changrui Liao e Yiping Wang. "Helicity Enhanced Torsion Sensor Based on Liquid Filled Twisted Photonic Crystal Fibers". Sensors 20, n. 5 (9 marzo 2020): 1490. http://dx.doi.org/10.3390/s20051490.

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A highly sensitive torsion sensor can be constructed by combining a twisted photonic crystal fiber with a liquid-filled waveguide in its air-hole cladding. The torsion sensitivity of this type of sensor is determined directly by the phase-matching conditions between the fiber core mode and the liquid waveguide mode, which can be improved by tuning the helicity (denoted by the initial twist rate, α0) of the twisted photonic crystal fiber. The enhancement mechanism of α0 on the sensitivity of the proposed torsion sensor is investigated theoretically, followed by experimental verifications, and a torsion sensitivity as high as 446 nm∙mm∙rad−1 can be obtained by tailoring these parameters. Experimental results show that the torsion sensitivity increases with α0 decreasing from 3.142 to 3.925 rad/mm, which are in consistence with that of the numerical predictions. The demonstrated torsion sensor is expected to contribute to the development of highly sensitive torsion-related photonic crystal fiber devices.

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Zhang, Hongyan, Jian Li, Can Jiang, Shili Chen, Zheng Fan e Yang Liu. "On propagation characteristics of ultrasonic guided waves in helical strands". AIP Advances 13, n. 2 (1 febbraio 2023): 025257. http://dx.doi.org/10.1063/5.0131295.

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Steel strands have been widely used in industrial fields as a reliable load-bearing component. Under the influence of environmental erosion and fatigue stress, different types of damage, such as corrosion and fracture, will occur in the in-service steel strands, which will cause unpredictable loss of personnel and property. Ultrasonic nondestructive testing technology has become an ideal testing method for long-distance metal structures in recent years due to the advantages of long detection distance and high efficiency. The detection effect of ultrasonic nondestructive testing technology largely depends on the propagation characteristics of the selected guided wave modes. However, due to the influence of the helical structure of the steel strands and the contact between the wires, the propagation characteristics of the guided waves in the steel strands are very complicated. In this paper, a method for analyzing the dispersion characteristics of steel strands based on the Floquet boundary conditions (Floquet BCs) is proposed. The essence of this method is the mutual transformation principle of wave solution and vibration solution. To adapt to the helical structure of steel strands, this paper proposes a helical coordinate system and twisted coordinate system and deduces the corresponding wavenumber conversion formula. The results of Floquet BCs are consistent with the semi-analytical finite element method and sweep frequency finite element modeling method, which proves the correctness of the Floquet BC method from both theoretical and experimental perspectives. This paper provides a new idea for analyzing the dispersion characteristics of complex waveguides such as steel strands.

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Ibarra-Villalon, H. E., O. Pottiez, A. Gómez-Vieyra, J. P. Lauterio-Cruz e Y. E. Bracamontes-Rodriguez. "Numerical study of polarization evolution governed by linear birefringence, twist-induced circular birefringence and nonlinear birefringence in a single-mode optical fiber". Journal of Optics 23, n. 12 (26 ottobre 2021): 123501. http://dx.doi.org/10.1088/2040-8986/ac2eaa.

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Abstract This tutorial presents a numerical analysis of continuous wave and ultrashort pulse evolution through a twisted single-mode optical fiber, modeled by the nonlinear Schrödinger equation. In this model, the polarization evolutions of the continuous wave and the pulse profile are studied by the changes in ellipticity and ellipse rotation, which are driven by the inherent linear birefringence of the optical fiber, the induced nonlinear birefringence due to the centrosymmetric response of the fiber and the induced circular birefringence due to a uniform twist applied along the fiber. In particular, the role of each birefringence effect is studied in detail. As a result, it is pointed out that a large uniform twist rate allows viewing the optical fiber as an isotropic waveguide that preserves ellipticity. On the other hand, a saturable absorber mechanism based on a linear polarizer and the ellipse rotation in a twisted fiber, which introduces a nonlinear transmission characteristic that is part of the principles of operation of the mode-locked fiber lasers, is analyzed in order to illustrate the applicability of this numerical study.

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Kudryavtsev, I. V., M. V. Brungardt, O. B. Gotseluk, O. I. Rabetskaya e A. A. Sharonov. "Elastic bend of twisted waveguide". Journal of Physics: Conference Series 1515 (aprile 2020): 042069. http://dx.doi.org/10.1088/1742-6596/1515/4/042069.

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Craig, Steven R., Zhenglu Li, Jiawei Ruan, Steven G. Louie e Chengzhi Shi. "Acoustic analog of twisted bilayer graphene". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A130. http://dx.doi.org/10.1121/10.0010876.

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The emergence of twistronics in bilayer graphene has inspired the creation of new phononic structures that translate quantum effects into macro systems. Here, we introduce an acoustic analog of twisted bilayer graphene that is built with 3D-printed star arrays confined in a two-dimensional acoustic waveguide. The lattices on the top and bottom of the waveguide are coupled by spoof surface acoustic waves. Like its quantum counterpart, the twisting angle of the structure influences wave propagation within the system and its resulting band structures. In analytical models, full-wave simulations, and experiments, we observe mode localization at magic twisting angle that hosts the flat bands. We also study other twisted bilayers with different twisting angles to compare with the magic-angle results. The observation of unusual twistronics effects in acoustic systems demonstrates the potential to identify new quantum materials with simplified acoustic models.

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Briet, Philippe, Hynek Kovařík, Georgi Raikov e Eric Soccorsi. "Eigenvalue Asymptotics in a Twisted Waveguide". Communications in Partial Differential Equations 34, n. 8 (27 luglio 2009): 818–36. http://dx.doi.org/10.1080/03605300902892337.

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Rico-Fernández, José, Álvaro F. Vaquero, Marcos R. Pino e Manuel Arrebola. "Fully Metallic Additively Manufactured Monopulse Horn Array Antenna in Ka-Band". Applied Sciences 14, n. 23 (28 novembre 2024): 11065. http://dx.doi.org/10.3390/app142311065.

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The Laser Powder-Bed Fusion Additive Manufacturing (LPBF AM) technique is evaluated for the manufacturing of fully metallic monolithic microwave components. To validate the manufacturing technique, a difference pattern array of 4 × 4 horn antennas is designed to operate at mm-Wave frequencies. The antenna is based on H-plane power dividers and a complex structure to obtain a difference radiation pattern by rotating twisted sections in two different orientations. The prototype is manufactured with a monolithic piece of aluminum alloy AlSi10Mg, providing a lightweight single structure that includes both radiating elements and a feeding network consisting of twisters and power dividers in a waveguide. The prototype was experimentally evaluated in an anechoic chamber and the near-field planar acquisition range, obtaining good agreement with full-wave simulations within an operational bandwidth from 34 to 36 GHz. The results demonstrate that the LPBF AM technique is a suitable candidate to produce challenging monolithic metal-only microwave components in the Ka-band, such as monopulse antennas.

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Chermoshentsev, Dmitry A., Evgeny V. Anikin, Sergey A. Dyakov e Nikolay A. Gippius. "Dimensional confinement and waveguide effect of Dyakonov surface waves in twisted confined media". Nanophotonics 9, n. 16 (26 ottobre 2020): 4785–97. http://dx.doi.org/10.1515/nanoph-2020-0459.

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AbstractWe theoretically study Dyakonov surface waveguide modes that propagate along the planar strip interfacial waveguide between two uniaxial dielectrics. We demonstrate that owing to the one-dimensional electromagnetic confinement, Dyakonov surface waveguide modes can propagate in the directions that are forbidden for the classical Dyakonov surface waves at the infinite interface. We show that this situation is similar to a waveguide effect and formulate the resonance conditions at which Dyakonov surface waveguide modes exist. We demonstrate that the propagation of such modes without losses is possible. We also consider a case of two-dimensional confinement, where the interface between two anisotropic dielectrics is bounded in both orthogonal directions. We show that such a structure supports Dyakonov surface cavity modes. Analytical results are confirmed by comparing with full-wave solutions of Maxwell’s equations. We believe that our work paves the way toward new insights in the field of surface waves in anisotropic media.

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Yan, Siqi, Ze Zhang, Weiqin Wang, Ziwen Zhou, Wenyi Peng, Yifan Zeng, Yuqin Yuan et al. "Photodetector Based on Twisted Bilayer Graphene/Silicon Hybrid Slot Waveguide with High Responsivity and Large Bandwidth". Photonics 9, n. 11 (17 novembre 2022): 867. http://dx.doi.org/10.3390/photonics9110867.

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Graphene/silicon hybrid photodetector operating at communication wavelength has attracted enormous attention recently due to its potential to realize bandwidth larger than 100 GHz. However, the responsivity is intrinsically limited by the low absorption from the atomic-thick graphene monolayer, which imposes significant obstacles towards its practical application. Although plasmonic structures has been widely applied to enhance the responsivity, it may induce the metallic absorption thus limit the responsivity lower than 0.6 A/W. Twisted bilayer graphene (TBG) has been reported to hold the ability to dramatically enhance the optical absorption due to the unique twist-angle-dependent van Hove singularities. In this article, we present a design of a silicon/TBG hybrid photodetector with a responsivity higher than 1 A/W and bandwidth exceeding 100 GHz. The enhanced responsivity is achieved by tuning the twisted angle of TBG to increase the absorption within the 1550 nm as well as utilizing the silicon slot waveguide to boost the mode overlap with TBG. The fabrication process of proposed design is also discussed demonstrating the advantages of low fabrication complexity. The proposed silicon/TBG photodetector could not only exhibit superior performance compared to previously reported silicon/monolayer graphene photodetector, but also pave the way for the practical application of graphene-based silicon optoelectronic devices.

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Маргушев, З. Ч., К. А. Бжеумихов e М. М. Назаров. "Протяженный гибкий терагерцевый волновод с малым ослаблением". Письма в журнал технической физики 49, n. 12 (2023): 22. http://dx.doi.org/10.21883/pjtf.2023.12.55569.19558.

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The possibility of fabricating a flexible extended terahertz waveguide with low losses, which has a hollow core and a reflective shell of eight polypropylene capillaries placed in a common shell with an outer diameter of 7.5 mm, has been demonstrated. The passage of terahertz pulses with frequencies of 2.3–2.8THz through a waveguide (including a twisted one, Rbent ∼60 cm) longer than 3 m with an attenuation of 5 dB/m has been experimentally confirmed.

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Choudhury, P. K. "Evanescent Field Enhancement in Liquid Crystal Optical Fibers: A Field Characteristics Based Analysis". Advances in Condensed Matter Physics 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/504868.

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The paper presents the analysis of the electromagnetic wave propagation through liquid crystal optical fibers (LCOFs) of two different types—conventional guides loaded with liquid crystals (addressed as LCOFs) and those with additional twists due to conducting helical windings (addressed as HCLCOFs). More precisely, the three-layer optical waveguide structures are considered along with its outermost region being loaded with radially anisotropic liquid crystal material and the inner regions being made of usual silica, as used in conventional optical fibers. In addition to that, LCOF with twists introduced in the form of conducting helical windings at the interface of the silica core and the liquid crystal clad is also taken into account. Emphasis has been put on the power confinements by the lower-order TE modes sustained in the different sections of the LCOF structure. The results demonstrate useful applications of these guides in integrated optics as the power sustained in the liquid crystal section by the excited TE modes remains very high. In the case of twisted clad liquid crystal guides, descriptions are limited to the nature of dispersion relation only under the TE mode excitation, and corresponding to the cases of helix orientations being parallel and perpendicular to the optical axis.

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Melnikov, Leonid, Vladimir Derbov e Alexei Bychenkov. "Dynamics of an off-axis gaussian beam with astigmatism and twist in a transparent nonlinear waveguide medium". Izvestiya VUZ. Applied Nonlinear Dynamics 6, n. 2 (1998): 73–84. http://dx.doi.org/10.18500/0869-6632-1998-6-2-73-84.

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Using the modified generalized moments method the equations of motion are derived for the parameters of а misaligned astigmatic twisted Gaussian beam in an axially symmetric nonlinear medium. Nontrivial features of the beam dynamics (e.g., phase locking, cycle generation, nonlinear symmetry change) in a parabolic waveguide with Kerr nonlinearity are revealed.

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Zhang, Zhi Dong, Nai Fu Wu, Wen Jiang Ye e Xuan Zhou. "Fully-Leaky Guided Mode Studies of Inverse Twisted Nematic Liquid Crystal". Advanced Materials Research 718-720 (luglio 2013): 1766–70. http://dx.doi.org/10.4028/www.scientific.net/amr.718-720.1766.

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The fully-leaky waveguide technique has been used to explore the director of inverse twisted nematic liquid crystal cell. The reflection data, including all the polarization-conserving signals Rpp and Rss as well as the polarization-conversion signals Rsp and Rps, are recorded under various voltages applied to the cell of 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, and 7.0V (rms), at a frequency of 1kHz. We found that this technique was sensitive to the director changes, especially for the polarization-conversion signals. Then by fitting angle-dependent reflectivity data to modeling theory, the arrangement of the director and some importance parameters of liquid crystal cell are obtained. It is proved that the reflectivity of fully-leaky waveguide mode can give the imperceptibility change in the cell.

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Borisov, Denis, e Giuseppe Cardone. "Planar waveguide with “twisted” boundary conditions: Small width". Journal of Mathematical Physics 53, n. 2 (febbraio 2012): 023503. http://dx.doi.org/10.1063/1.3681895.

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Borisov, Denis, e Giuseppe Cardone. "Planar waveguide with “twisted” boundary conditions: Discrete spectrum". Journal of Mathematical Physics 52, n. 12 (dicembre 2011): 123513. http://dx.doi.org/10.1063/1.3670875.

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42

Filgueiras, Hugo Rodrigues Dias, James R. Kelly, Pei Xiao, I. F. da Costa e Arismar Cerqueira Sodré. "Wideband Omnidirectional Slotted-Waveguide Antenna Array Based on Trapezoidal Slots". International Journal of Antennas and Propagation 2019 (13 ottobre 2019): 1–8. http://dx.doi.org/10.1155/2019/3792980.

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This manuscript presents a novel approach for designing wideband omnidirectional slotted-waveguide antenna arrays, which is based on trapezoidal-shaped slots with two different electrical lengths, as well as a twisted distribution of slot groups along the array longitudinal axis. The trapezoidal section is formed by gradually increasing the slot length between the waveguide interior and exterior surfaces. In this way, a smoother impedance transition between waveguide and air is provided in order to enhance the array operating bandwidth. In addition, we propose a twisting technique, responsible to improve the omnidirectional pattern, by means of reducing the gain ripple in the azimuth plane. Experimental results demonstrate 1.09 GHz bandwidth centered at 24 GHz (4.54% fractional bandwidth), gain up to 14.71 dBi over the operating bandwidth, and only 2.7 dB gain variation in the azimuth plane. The proposed antenna array and its enabling techniques present themselves as promising solutions for mm-wave application, including 5G enhanced mobile broadband (eMBB) communications.

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43

Wu, Jun-mo, Dong-fang Zhou, Xue Lei, Jun Gao e Hao-ming Hu. "Design of a Compact Broadband 90° Waveguide Twist Based on Double-Corner-Cut Square Slots". International Journal of Antennas and Propagation 2017 (2017): 1–5. http://dx.doi.org/10.1155/2017/8657620.

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A new compact broadband waveguide twist by double-corner-cut square slots is presented. In particular, the proposed module is made from two substrate layers and three copper cladding layers, which can be used as the waveguide twist and broadband filter. A double-corner-cut square slot is etched on each metal layer with relative rotation. It is found that the optimized module can provide the bandwidths of no less than 6.1% at the 10-dB return-loss level or 4.3% at the 20-dB level with a minimum length of 0.07 waveguide width.

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44

Vavulin, D. N., e A. A. Sukhorukov. "Quantum walks of photon pairs in twisted waveguide arrays". Journal of Physics: Conference Series 643 (2 novembre 2015): 012050. http://dx.doi.org/10.1088/1742-6596/643/1/012050.

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45

Kovařík, H., e D. Krejčiřík. "A Hardy inequality in a twisted Dirichlet–Neumann waveguide". Mathematische Nachrichten 281, n. 8 (agosto 2008): 1159–68. http://dx.doi.org/10.1002/mana.200610667.

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46

Sun, Haibin, Cai Feng, Yongjun Huang, Ruiming Wen, Jian Li, Weijian Chen e Guangjun Wen. "Dual-Band Notch Filter Based on Twist Split Ring Resonators". International Journal of Antennas and Propagation 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/541264.

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A novel dual-band rectangular waveguide notch filter is experimentally investigated in this paper. Such filter is realized by integrating two pairs of split ring resonators (SRRs) printed on the two sides of a dielectric slab with twist angles and separated as a distance in the center of the rectangular waveguide. Due to the coupling effects between the twist SRRs and between the original SRRs and their mirror images generated by the metallic walls perpendicular to the E-field direction, it can flexibly contribute two disjunct resonance states and result in the dual-band notch properties. Furthermore, the two resonance frequencies can be controlled by changing the twist angles, resulting in the shifts of notch frequency bands.

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47

Briet, Ph, J. Dittrich e D. Krejčiřík. "Absolute continuity of the spectrum in a twisted Dirichlet-Neumann waveguide". Journal of Mathematical Physics 61, n. 1 (1 gennaio 2020): 013503. http://dx.doi.org/10.1063/1.5114994.

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48

Min-Cheol Oh e Sang-Yung Shin. "Polymeric polarization-independent modulator incorporating twisted optic-axis waveguide polarization converters". IEEE Photonics Technology Letters 8, n. 11 (novembre 1996): 1483–85. http://dx.doi.org/10.1109/68.541557.

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Wang, Kai, Chih-Ping Lin e Wei-Hao Jheng. "A New TDR-Based Sensing Cable for Improving Performance of Bridge Scour Monitoring". Sensors 20, n. 22 (21 novembre 2020): 6665. http://dx.doi.org/10.3390/s20226665.

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The use of time domain reflectometry (TDR) for real-time monitoring of bridge scour process has gone through several stages of development. The recently-proposed concept of bundled TDR sensing cable, in which two sets of insulated steel strands are twisted around and connected to a central coaxial cable to form a compact sensing cable, is a major change that has several advantages including the bottom-up sensing mechanism. Nevertheless, there is big room for improving its measurement sensitivity and signal to noise ratio (SNR). Changes in waveguide configuration also need to be made to avoid the adverse effect of insulation abrasion observed in field implementation. This study evaluated three new conductor and insulator configurations for constructing the sensing waveguide, including a balanced two-conductor waveguide (Type I), an unbalanced three-conductor waveguide with insulation coating on the middle conductor (Type II) and an unbalanced three-conductor with insulation coating on the two outer conductors (Type III). In all cases, the spacing between the two sets of steel strands (i.e., the waveguide conductors) was especially enlarged by replacing some steel strands with non-conductor wires to increases measurement sensitivity and avoid shorted conditions due to insulation abrasion. Experimental results show that Type III has the best performance on all counts. A new improved TDR sensing cable was hence proposed based on Type III configuration. Its performance was further evaluated by a full-scale experiment to take into consideration the long range of measurement in most field conditions. Detailed discussions on improvements of measurement sensitivity and SNR, limitation of sensing range, and mitigating the adverse effect of insulation abrasion are presented.

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Bagheriasl, Mohammad, e Guido Valerio. "Bloch Analysis of Electromagnetic Waves in Twist-Symmetric Lines". Symmetry 11, n. 5 (3 maggio 2019): 620. http://dx.doi.org/10.3390/sym11050620.

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We discuss here under which conditions a periodic line with a twist-symmetric shape can be replaced by an equivalent non-twist symmetric structure having the same dispersive behavior. To this aim, we explain the effect of twist symmetry in terms of coupling among adjacent cells through higher-order waveguide modes. We use several waveguide modes to accurately derive the dispersion diagram of a line through a multimodal transmission matrix. With this method, we can calculate both the phase and attenuation constants of Bloch modes, both in shielded and open structures. In addition, we use the higher symmetry of these structures to further reduce the computational cost by restricting the analysis to a subunit cell of the structure instead of the entire unit cell. We confirm the validity of our analysis by comparing our results with those of a commercial software.

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