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Influence of temperature on ultrasound absorption in waveguides made out of refractory materials

ULTRASONICS 2015年 61卷 33-39页

作者： Kozhemyakin, G. N. Bulankina, A. A. Volodymyr Dahl East Ukrainian Natl Univ Dept Micro & Nanoelect UA-91034 Lugansk Ukraine

We studied the influence of temperature increase to 1500 degrees C on ultrasound absorption at frequencies from 0.1 to 1.0 MHz in tungsten, molybdenum, vanadium, graphite, and fused silica. The ultrasound absorption coefficient in these materials was calculated. It was shown that the fused silica has the smallest ultrasound absorption coefficient for temperatures up to 1000 degrees C. Vanadium and graphite also have small values of this coefficient for the considered temperature. The ultrasound absorption was investigated experimentally in graphite and fused silica waveguides. We demonstrated that the ultrasound absorption did not change in graphite with the temperature increase, but it increased in fused silica by a factor 2 for the temperature above 1000 degrees C. We show that different acoustical and mechanical properties of vanadium, graphite, and fused silica allow using them for waveguide applications and buffer rods in crystal growth at temperatures below 1500 degrees C and ultrasound frequency below 1.0 MHz. (C) 2015 Elsevier B.V. All rights reserved.

关键词： waveguides Buffer rods Crystal growth Ultrasound absorption Ultrasound intensity

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Anisotropic build-up of photo-induced waveguides in biased photorefractive media

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OPTICS COMMUNICATIONS 2015年 355卷 382-390页

作者： Coda, Virginie Ciret, Charles Mengis, Thibault Gorram, Mohamed Montemezzani, Germano Chauvet, Mathieu Devaux, Fabrice Univ Lorraine LMOPS EA 4423 F-57070 Metz France CentraleSupelec LMOPS EA 4423 F-57070 Metz France Univ Franche Comte UMR CNRS 6174 FEMTO ST Inst F-25000 Besancon France

We study the anisotropic dynamic formation of photo-induced waveguide in biased photorefractive media by means of a time resolved three-dimensional numerical model of the space-charge field formation. Specific features of the dynamic creation of 1D-confined planar and 2D-confined channel waveguides are elucidated and confirmed experimentally. Thanks to a transient space-charge field overshooting in both 1D and 2D geometries, light confinement in the first dimension occurs at a very early stage in the formation of the space-charge field. In the 2D channel type waveguides, the final shape of the waveguide index contrasts and modes depend not only on the illumination geometry and intensity distribution, but also on the anisotropy of the charge mobility along the two transverse directions. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Photorefractive material Photo-induced structures waveguides

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Numerical Analysis of Transient Wave Propagation in Nonlinear One-Dimensional waveguides by Using the Spectral Finite Element Method

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JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS 2015年第5期10卷 051003页

作者： Liu, Yu Dick, Andrew J. Rice Univ Nonlinear Phenomena Lab Dept Mech Engn & Mat Sci Houston TX 77005 USA

In this paper, transient wave propagation in nonlinear one-dimensional (1D) waveguides is studied. A complete nonlinear (CN) 1D model accounting for both axial and transverse displacements is developed and geometric and material nonlinearities are separately modeled. The alternating frequency-time finite element method (AFT-FEM) is implemented for this complete 1D model. Numerical simulations are conducted and the response behaviors for axial and transverse motions are analyzed. Comparison of the responses for the geometrically nonlinear (GN) model with a corresponding linear model supports predictions made from the previous analytical studies that the geometric non-linearity has limited influence on the response of transient transverse waves in the intermediate strain regime. On the contrary, strong nonlinear behavior appears in the response for the materially nonlinear (MN) models. Depending on the local nonlinear property of the material in the intermediate strain regime, the amplitude of the response can be significantly influenced and additional dispersion can be introduced into the response. An exploration of the interaction between the geometric nonlinearity and the material nonlinearity for a rod model in a large strain regime is also conducted and the responses are analyzed by using time-frequency analysis. The competing effect of the geometric nonlinearity and the material nonlinearity can result in a pseudolinear response in a strong nonlinear system for a given range of impact loading.

关键词： Waves Stress Wave propagation Modeling waveguides Numerical analysis Finite element methods Finite element model Computer simulation Transients (Dynamics)

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Plug-and-Play Fiber-Coupled Quantum Dot Single-Photon Source via Photonic Wire Bonding

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ADVANCED QUANTUM TECHNOLOGIES 2024年第1期7卷

作者： De Gregorio, Marco Yu, Shangxuan Witt, Donald Lin, Becky Mitchell, Matthew Dusanowski, Lukasz Schneider, Christian Chrostowski, Lukas Huber-Loyola, Tobias Hoefling, Sven Young, Jeff F. Pfenning, Andreas Julius Maximilians Univ Wurzburg Phys Inst Lehrstuhl Tech Phys D-97074 Wurzburg Germany Univ British Columbia Stewart Blusson Quantum Matter Inst Vancouver BC V6T 1Z4 Canada Univ British Columbia Dept Elect & Comp Engn 2332 Main Mall Vancouver BC V6T 1Z4 Canada Princeton Univ Dept Elect & Comp Engn Princeton NJ 08544 USA Carl von Ossietzky Univ Oldenburg Inst Phys D-26129 Oldenburg Germany Carl von Ossietzky Univ Oldenburg Ctr Nanoscale Dynam D-26129 Oldenburg Germany Univ British Columbia Dept Phys & Astron Vancouver BC V6T 1Z1 Canada

The collection of single-photon emission from a quantum dot (QD) in a Bragg waveguide through a photonic wire bond (PWB) via free-space resonant frequency pumping at 1.6 K is demonstrated. The in-fiber single photons show a small multiphoton contribution, quantified by a low second order photon autocorrelation value of g(corr)((2))(0)=(5.9 +/- 0.8)x10(-3) (background-corrected) or graw((0))((2)) = (9.5 +/- 1.4)x10(-2) (raw data). The decay time of the QD is measured to be tau=440 ps. The PWB obviates the need for in-cryostat alignment of the single-photon source with an optical fiber and thus offers a route to scalable integration of quantum photonic devices in a cryogenic environment. Uniquely, the approach combines the QD-waveguide technique, enabling resonant driving of individual QDs without the need for cross-polarization filtering, and the PWB for deterministic, alignment-free coupling of single-photon sources to optical fibers. The combination of a single-photon source in a ridge waveguide with a photonic wire bond (PWB) connected to the end-facet is demonstrated. After cooling the sample to 1.6 K, decay time and second-order autocorrelation under pulsed, resonant optical excitation are analyzed. The findings herein highlight the possibility of using PWBs at low temperatures as an interface for single-photon ***

关键词： III-V semiconductors photonic wire bonds quantum dots single-photon sources waveguides

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Application of the matrix element method: A mode-matching approach for wave-bearing cavities in complex media

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CHAOS SOLITONS & FRACTALS 2024年 189卷

作者： Bilal, Hazrat Afzal, Muhammad Govt Postgrad Coll Dept Math Mardan Pakistan Capital Univ Sci & Technol Dept Math Islamabad Pakistan Gulf Univ Sci & Technol Ctr Appl Math & Bioinformat Dept Math & Nat Sci Hawally 32093 Kuwait

The present study employs an analytical scheme useful for investigating the reflection, transmission, and absorption of fluid-structure coupled waves in a dissipative device with flexible boundaries. The method based on contour integration, which avoids the cumbersome root-finding processes for complex dispersion relations, thereby eliminating the error of missing roots. The procedure involves applying the mode matching technique along with the generalized orthogonality relation to transform the differential system into linear algebraic systems. The matrix elements involve unknown wavenumbers in the finite chamber with wave bearing boundaries and porous material filling the cavity region, separated from air by a screen. Due to the absorbing properties of the medium, the wavenumbers are complex, and the matrix elements are reformulated using contour integration without needing explicit information about the wavenumbers. It is found that changing the properties of absorbent material and membrane parameters the attenuation behavior can optimized.

关键词： Fluid-structure coupled wave Complex media properties waveguides Scattering characteristics Mode matching technique

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Engineering the Breaking of Topological Protection in Valley Photonic Crystals Enables to Design Chip Level Functions for THz 6G Communications and Beyond

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2024年第23期42卷 8323-8335页

作者： Mohammed, Abdu Subahan Leveque, Gaetan Lebouvier, Edouard Pennec, Yan Faucher, Marc Amo, Alberto Szriftgiser, Pascal Ducournau, Guillaume Univ Lille Univ Polytech Hauts Defrance Inst Elect Microelect & Nanotechnol CNRSCentraleLilleIEMNUMR 8520 F-59000 Lille France Univ Lille CNRS PhLAM Lab Phys Lasers Atomes & MolUMR 8523 F-59000 Lille France

The realization of integrated, low-loss, and efficient systems for data-intensive applications such as augmented and virtual reality requires on-chip integrated photonic circuits, which have great potential for advanced information and communication technologies, including 6G wireless networks and intra- and inter-chip communication systems. A promising platform for achieving this revolution is Valley Photonic Crystals (VPCs). VPCs enable the construction of topological interfaces, which facilitate the propagation of light with minimal losses and backscattering through unidirectional edge modes. Interfacial topological interfaces and the degree of topological protection experienced by these robust edge modes is a relatively new perspective worth exploring. The ever-increasing demand for faster data rates in data-intensive applications like augmented and virtual reality necessitates the exploration of frequencies beyond the conventional 300 GHz band. In this study, we introduce variations in topological protection by considering different interfacial designs and suitable air-hole geometries for passive functional devices. We show that the partial breakup of topological protection can be an asset for the design of on-chip passive functionalities. We focus on bearded and zigzag junctions and appropriate air hole geometries for VPC unit cells. To experimentally verify the scalability of topological protection, we demonstrate the performance of terahertz (THz) topological ring resonators and THz double cavity resonators designed for operation in the 600 GHz frequency region. This work showcases how the scaling of topological protection can be achieved by utilizing a combination of air hole geometry and interfacial degrees of freedom, providing functional tuning of devices at the chip level.

关键词： Terahertz communications Protection Photonics Photonic crystals Optical waveguides Optical ring resonators Geometry Terahertz topological photonics waveguides

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A Physics-Informed Neural Network-Based Waveguide Eigenanalysis

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IEEE ACCESS 2024年 12卷 120777-120787页

作者： Khan, Md Rayhan Zekios, Constantinos L. Bhardwaj, Shubhendu Georgakopoulos, Stavros V. Florida Int Univ Dept Elect & Comp Engn Miami FL 33174 USA Univ Nebraska Lincoln Dept Elect & Comp Engn Lincoln NE 68588 USA

This work presents a deep neural network (DNN)-based approach for identifying the modal field distributions of closed non-radiating waveguides. Specifically, physics-informed neural networks (PINNs) are used to solve the Helmholtz partial differential equation. The PINN architecture includes incorporation of boundary conditions and selection of initial conditions to obtain required modes inside the waveguides. In this paper, furthermore, the use of this method is illustrated for waveguides consisting of inhomogeneous and anisotropic media, where we apply a domain decomposition-based deep learning method. Our approach successfully identifies all eigenmode distributions with an error of less than -12 dB as compared to analytical and full-wave simulation results. Notably, we further enhance the efficiency of our approach by utilizing transfer learning, achieving a 23 times reduction in solution time. Our results demonstrate PINNs as an alternative to traditional methods in accurately calculating waveguide modal field distributions and its applicability to other partial differential equation based EM problems.

关键词： Electromagnetic waveguides Training Optical waveguides Boundary conditions Anisotropic Computer architecture Rectangular waveguides Neural networks Physics computing Transfer learning Eigenvalues and eigenfunctions Physics-informed neural network deep learning domain decomposition transfer learning eigenanalysis waveguides

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Defect-induced discrete breather in dissipative optical lattices with weak nonlinearity

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OPTICS EXPRESS 2024年第12期32卷 20503-20514页

作者： Bai, Xiao-Dong Xu, Tianhong Zhao, Yujia Li, Yengbo Ji, Guopeng Zhao, Jincui Hebei Normal Univ Coll Phys Shijiazhuang 050024 Peoples R China Hebei Normal Univ Hebei Key Lab Photophys Res & Applicat Shijiazhuang 050024 Peoples R China Shijiazhuang Tiedao Univ Dept Math & Phys Shijiazhuang 050043 Peoples R China Shijiazhuang Tiedao Univ Inst Appl Phys Shijiazhuang 050043 Peoples R China

It is widely believed that the discrete breather (DB) can only be created when the nonlinearity is strong in nonlinear systems. However, we here establish that this belief is incorrect. In this work, we systemically investigate the generation of DBs induced by coupling of the defects and nonlinearity for Bose-Einstein condensates in dissipative optical lattices. The results show that, only in a clean lattice is strong nonlinearity a necessary condition for generating of DB;whereas, if the lattice has a defect, the DBs can also be discovered even in weak nonlinearity, and its generation turns out to be controllable. In addition, we further reveal a critical interval of the defect in weak nonlinearity, within which DBs can be found, while outside DBs do not exist. Furthermore, we also explore the impact of multiple defects on the generation of DBs, and analyze the underlying physical mechanisms of these interesting phenomena. The results not only have the potential to be used for more precise engineering in the DB experiments, but also suggest that the DB may be ubiquitous since the defects and dissipation are unavoidable in real physics.

关键词： Anderson localization Bose Einstein condensates Numerical simulation Optical lattices Optical trapping waveguides

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Ultrahigh Q SOI ring resonator with a Hermite or B-spline curved waveguide

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APPLIED OPTICS 2024年第23期63卷 6233-6239页

作者： Tao, Pengyu Yan, Boxia Bai, Mou Zhou, Mi Sun, Chenxi Qi, Yan Wang, Yanwei Han, Zhe Fan, Yuanyuan Wang, Qian Univ Chinese Acad Sci Beijing 100049 Peoples R China Chinese Acad Sci Inst Microelect Beijing 100029 Peoples R China Guangxi Transportat Sci & Technol Grp Co Ltd Nanning 530000 Peoples R China

Two new, to the best of our knowledge, designs for a huge, single-mode operation, ultrahigh quality factor SOI ring resonators based on the 90 degrees bend of the B-spline curve and the Hermite curve were demonstrated. The ring resonators comprise multimode straight strip waveguides (MMWG), single-mode strip waveguides (SMWG), 90 degrees bends, and tapers. The TE0-TE0 transmission loss of the bends can reach 0.000013 dB and 0.000091 dB, and the TE0-TE1 excitation ratios reach -48 dB and -50 dB, respectively, when the bends were designed using the Hermite curve or B-spline curve. Two SOI ring resonators of about 3.00 cm length consisting of the structures mentioned above are manufactured. The first was made up of Hermite curves with 90 degrees bends. It could achieve a Q factor of 4.65 x 106 and a free spectrum range (FSR) of 0.025 nm. The second one employed B-spline curves with 90 degrees bends. It could reach a Q factor of 4.37 x 106 and FSR of 0.022 nm. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： Bend loss Optical systems Q factor Ring resonators Waveguide design waveguides

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Modal analysis of waveguide for the study of frequency bandgaps of a bounded periodic medium

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JOURNAL OF SOUND AND VIBRATION 2024年 572卷

作者： Darche, M. Lopez-Caballero, F. Tie, B. Univ Paris Saclay Cent Supelec CNRS LMPS Lab Mech Paris SaclayENS Paris Saclay F-91190 Gif Sur Yvette France

A novel method based on waveguide modal analysis is presented to evaluate the effectiveness in terms of frequency bandgaps of bounded periodic metamaterials. The effect of the size of the bounded medium, i.e., the number of periodic unit cells, on the frequency bandgaps predicted by Floquet-Bloch theory in the infinite case is investigated and quantified. The waveguides considered in this work have a bounded cross-section and an infinite longitudinal axis simulated by Perfectly Matched Layers. Its useful area is made of a bounded 1D or 2D -periodic matrixinclusion metamaterial. In the 2D -periodic case, an approach combining the waveguide modal analysis with the Floquet-Bloch transform is further proposed. Applying the proposed method, the SH-waves propagating in a waveguide are studied by using the finite element method. The discrete spectrum of the waveguide and the associated attenuated or trapped wave modes are calculated and analyzed, which provides, within a semi -analytic framework, an exact characterization regarding the attenuation coefficient and the frequency bandgaps of the studied bounded periodic medium. More particularly, effectiveness indicators are defined to compare the width and the position of frequency bandgaps between the bounded and infinite cases as a function of the cell number. Last but not least, the proposed method is also successfully applied to bounded periodic media with local resonators to characterize their filtering and attenuation effectiveness, which shows its interest in such a case of great practical interest.

关键词： Metamaterials Floquet-Bloch theory Seismic waves Modal analysis waveguides Bounded periodic medium

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