1
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Fakheri MH, Abdolali A. Ultrathin carpet cloak enabled by infinitely anisotropic medium. Sci Rep 2023; 13:17695. [PMID: 37848664 PMCID: PMC10582059 DOI: 10.1038/s41598-023-44984-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Accepted: 10/14/2023] [Indexed: 10/19/2023] Open
Abstract
Thanks to the pioneering studies conducted on the fields of transformation optics (TO) and metasurfaces, many unprecedented devices such as invisibility cloaks have been recently realized. However, each of these methods has some drawbacks limiting the applicability of the designed devices for real-life scenarios. For instance, TO studies lead to bulky coating layer with the thickness that is comparable to, or even larger than the dimension of the concealed object. In this paper, based on the coordinate transformation, an ultrathin carpet cloak is proposed to hide objects with arbitrary shape and size using a thin anisotropic material, called as infinitely anisotropic medium (IAM). It is shown that unlike the previous metasurface-based carpet cloaks, the proposed IAM hides objects from all viewing incident angles while it is extremely thin compared with the object dimensions. This material also circumvents the conventional transformation optics' complexities and could be easily implemented in practical scenarios. To demonstrate the capability of the proposed carpet cloak, several full-wave simulations are carried out. Finally, as a proof of concept, the IAM is implemented based on the effective medium theory which exhibits good agreement with the results obtained from the theoretical investigations. The introduced material not only constitutes a significant step towards the invisibility cloak but also can greatly promote the practical application of the other TO-based devices.
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Affiliation(s)
- Mohammad Hosein Fakheri
- Applied Electromagnetic Laboratory, School of Electrical Engineering, Iran University of Science and Technology, Tehran, 1684613114, Iran
| | - Ali Abdolali
- Applied Electromagnetic Laboratory, School of Electrical Engineering, Iran University of Science and Technology, Tehran, 1684613114, Iran.
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2
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Developing a carpet cloak operating for a wide range of incident angles using a deep neural network and PSO algorithm. Sci Rep 2023; 13:670. [PMID: 36635479 PMCID: PMC9837171 DOI: 10.1038/s41598-023-27458-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 01/02/2023] [Indexed: 01/13/2023] Open
Abstract
Designing invisibility cloaks has always been one of the most fascinating fields of research; in this regard, metasurface-based carpet cloaks have drawn researchers' attention due to their inherent tenuousness, resulting in a lower loss and easier fabrication. However, their performances are dependent on the incident angle of the coming wave; as a result, designing a carpet cloak capable of rendering objects under it invisible for a wide range of angles requires advanced methods. In this paper, using the Particle Swarm Optimization (PSO) algorithm, along with a trained neural network, a metasurface-based carpet cloak is developed capable to operate for a wide range of incident angles. The deep neural network is trained and used in order to accelerate the process of calculation of reflection phases provided by different unit cell designs. The resultant carpet cloak is numerically analyzed, and its response is presented and discussed. Both near-field and far-field results show that the designed carpet cloak operates very well for all incident angles in the range of 0 to 65 degrees.
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3
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Eskandari H. Strictly conformal transformation optics for directivity enhancement and unidirectional cloaking of a cylindrical wire antenna. Sci Rep 2022; 12:16278. [PMID: 36175589 PMCID: PMC9522858 DOI: 10.1038/s41598-022-20503-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 09/14/2022] [Indexed: 11/09/2022] Open
Abstract
Using conformal transformation optics, a cylindrical shell made of an isotropic refractive index material is designed to improve the directivity of a wire antenna while making it unidirectionally invisible. If the incident wave comes from a specific direction, it is guided around the wire. Furthermore, when an electrical current is used to excite the wire, the dielectric shell transforms the radiated wave into two lateral beams, improving directivity. The refractive index of the dielectric shell is calculated using the transformation optics recipe after establishing a closed-form conformal mapping between an annulus and a circle with a slit. The refractive index is then modified and discretized using a hexagonal lattice. Ray-tracing and full-wave simulations with COMSOL Multiphysics are used to validate the functionality of the proposed shell.
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Affiliation(s)
- Hossein Eskandari
- Department of Electrical Engineering, Ferdowsi University of Mashhad, 9177948944, Mashhad, Iran.
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4
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Cai T, Zheng B, Lou J, Shen L, Yang Y, Tang S, Li E, Qian C, Chen H. Experimental Realization of a Superdispersion-Enabled Ultrabroadband Terahertz Cloak. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2205053. [PMID: 35926151 DOI: 10.1002/adma.202205053] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 07/26/2022] [Indexed: 06/15/2023]
Abstract
Invisibility has been a topic of long-standing interest owing to the advent of metamaterials and transformation optics, but still faces open challenges after its tremendous development in recent decades. One of the big challenges is the narrow bandwidth, as the realization of an invisibility cloak is usually based on a metamaterial-an artificial composite material composed of subwavelength resonator structures that are always associated with dispersion. Different from previous works that have tried to eliminate the material dispersion to enhance the bandwidth of an invisibility cloak, here, it is found that by judiciously harnessing the material dispersion, the bandwidth of the cloak can still be significantly increased. Interestingly, the material dispersion does not violate the law of causality. As a proof of concept, an ultrabroadband terahertz (THz) carpet cloak is experimentally demonstrated through an array of superdispersive microparticles, rendering the target object invisible to detection by both time- and frequency-domain wideband systems. The work presents a feasible invisibility strategy that is closer to practical applications and may pave a brand-new way for the development of dispersion-dominated ultrabroadband metadevices.
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Affiliation(s)
- Tong Cai
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310027, P. R. China
- Air and Missile Defend College, Air Force Engineering University, Xi'an, 710051, P. R. China
- International Joint Innovation Center, Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang, The Electromagnetics Academy at Zhejiang University, Zhejiang University, Haining, 314400, P. R. China
| | - Bin Zheng
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310027, P. R. China
- International Joint Innovation Center, Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang, The Electromagnetics Academy at Zhejiang University, Zhejiang University, Haining, 314400, P. R. China
| | - Jing Lou
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310027, P. R. China
- Air and Missile Defend College, Air Force Engineering University, Xi'an, 710051, P. R. China
| | - Lian Shen
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Yihao Yang
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Shiwei Tang
- Department of Physics, Faculty of Science, Ningbo University, Ningbo, 315211, P. R. China
| | - Erping Li
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Chao Qian
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310027, P. R. China
- International Joint Innovation Center, Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang, The Electromagnetics Academy at Zhejiang University, Zhejiang University, Haining, 314400, P. R. China
| | - Hongsheng Chen
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310027, P. R. China
- International Joint Innovation Center, Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang, The Electromagnetics Academy at Zhejiang University, Zhejiang University, Haining, 314400, P. R. China
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5
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Tan Q, Zheng B, Cai T, Qian C, Zhu R, Li X, Chen H. Broadband Spin-Locked Metasurface Retroreflector. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2201397. [PMID: 35543518 PMCID: PMC9284148 DOI: 10.1002/advs.202201397] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Indexed: 05/31/2023]
Abstract
Retroreflectors are ubiquitously used in a multitude of applications, such as cloaking, wireless communication, radar, and antenna, owing to their ability to augment the reflected electromagnetic (EM) waves in the incident direction. However, Current metasurface retroreflector designs have yet to mature into a practical method due to the limitations of low efficiency and narrow band, which actually originate from the difficulty in simultaneously engineering phase profiles of certain metasurface at distinct wavelengths. Here, a broadband spin-locked retroreflector with high efficiency that relies only on a simple metasurface layer is demonstrated. The metasurface is designed with low-loss dielectric resonators, introducing both the propagation and geometric phases to enable dispersive phase compensation. The results indicate that the proposed metasurface can achieve retroreflection over a broadband spectrum while keeping the spin state identical. Furthermore, a broadband spin-locked cloak is presented for validation. The work builds up a major advance for practice-oriented retroreflector and even envision this approach may open new vistas in the very cutting-edge research of 6G wireless communication network.
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Affiliation(s)
- Qingze Tan
- Interdisciplinary Center for Quantum InformationState Key Laboratory of Modern Optical InstrumentationZJU‐Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhou310027China
- International Joint Innovation CenterKey Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of ZhejiangThe Electromagnetics Academy at Zhejiang UniversityZhejiang UniversityHaining314400China
- Jinhua Institute of Zhejiang UniversityZhejiang UniversityJinhua321099China
| | - Bin Zheng
- Interdisciplinary Center for Quantum InformationState Key Laboratory of Modern Optical InstrumentationZJU‐Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhou310027China
- International Joint Innovation CenterKey Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of ZhejiangThe Electromagnetics Academy at Zhejiang UniversityZhejiang UniversityHaining314400China
- Jinhua Institute of Zhejiang UniversityZhejiang UniversityJinhua321099China
| | - Tong Cai
- Interdisciplinary Center for Quantum InformationState Key Laboratory of Modern Optical InstrumentationZJU‐Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhou310027China
- Air and Missile Defend CollegeAir force Engineering UniversityXi'an710051China
| | - Chao Qian
- Interdisciplinary Center for Quantum InformationState Key Laboratory of Modern Optical InstrumentationZJU‐Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhou310027China
- International Joint Innovation CenterKey Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of ZhejiangThe Electromagnetics Academy at Zhejiang UniversityZhejiang UniversityHaining314400China
- Jinhua Institute of Zhejiang UniversityZhejiang UniversityJinhua321099China
| | - Rongrong Zhu
- Interdisciplinary Center for Quantum InformationState Key Laboratory of Modern Optical InstrumentationZJU‐Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhou310027China
- School of Information and Electrical EngineeringZhejiang University City CollegeHangzhou310015China
| | - Xiaofeng Li
- Interdisciplinary Center for Quantum InformationState Key Laboratory of Modern Optical InstrumentationZJU‐Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhou310027China
- Air and Missile Defend CollegeAir force Engineering UniversityXi'an710051China
| | - Hongsheng Chen
- Interdisciplinary Center for Quantum InformationState Key Laboratory of Modern Optical InstrumentationZJU‐Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhou310027China
- International Joint Innovation CenterKey Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of ZhejiangThe Electromagnetics Academy at Zhejiang UniversityZhejiang UniversityHaining314400China
- Jinhua Institute of Zhejiang UniversityZhejiang UniversityJinhua321099China
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6
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Tian X, Xu J, Xu K, Qian Y, Ma X, Yang P, Duan X, Ding P, Li ZY. Phase-change reconfigurable metasurface for broadband, wide-angle, continuously tunable and switchable cloaking. OPTICS EXPRESS 2021; 29:5959-5971. [PMID: 33726127 DOI: 10.1364/oe.418200] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 01/29/2021] [Indexed: 06/12/2023]
Abstract
Being invisible at will has fascinated humanity for centuries and it has become more tangible with the development of metasurfaces, which have demonstrated the extraordinary ability of wavefront manipulation. However, state-of-the-art invisibility cloaks typically work in a deterministic system with a limited bandwidth and small incident angle ranges. Here, by integrating the phase-change material of Ge2Sb2Te5 and the wavefront tailoring functionality of a reflective metasurface, we have achieved a unique carpet cloak that is endowed with broadband invisibility from 6920 to 8220 nm, fully concealing objects over a wide angular span of ±25° and a prominent radar cross-section reduction. Furthermore, the central cloaking wavelength can be continuously tuned with Ge2Sb2Te5 film under different intermediate phases by precisely controlling external stimuli, which will provide a flexible and encouraging way to achieve active features once fabricated. Simulation results also show that the cloaking bandwidth can be significantly extended by triggering Ge2Sb2Te5 from the amorphous to crystalline states. Importantly, the hybrid metasurface can realize switching of "ON" and "OFF" states in terms of cloaking features by converting Ge2Sb2Te5 from the amorphous to the crystalline state. To the best of our knowledge, this is the first metasurface carpet cloak that utilizes the phase-change material of Ge2Sb2Te5 to achieve ultra-broadband, wide-angle, continuously tunable and switchable cloaking with low profiles, light weights, and easy access. This design of a reconfigurable cloak is expected to find potential applications in various areas such as vehicle cloaking, illusions and so on.
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7
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Non-closed acoustic cloaking devices enabled by sequential-step linear coordinate transformations. Sci Rep 2021; 11:1845. [PMID: 33469105 PMCID: PMC7815784 DOI: 10.1038/s41598-021-81331-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 01/05/2021] [Indexed: 11/25/2022] Open
Abstract
Hitherto acoustic cloaking devices, which conceal objects externally, depend on objects' characteristics. Despite previous works, we design cloaking devices placed adjacent to an arbitrary object and make it invisible without the need to make it enclosed. Applying sequential linear coordinate transformations leads to a non-closed acoustic cloak with homogeneous materials, creating an open invisible region. Firstly, we propose to design a non-closed carpet cloak to conceal objects on a reflecting plane. Numerical simulations verify the cloaking effect, which is completely independent of the geometry and material properties of the hidden object. Moreover, we extend this idea to achieve a directional acoustic cloak with homogeneous materials that can render arbitrary objects in free space invisible to incident radiation. To demonstrate the feasibility of the realization, a non-resonant meta-atom is utilized which dramatically facilitated the physical realization of our design. Due to the simple acoustic constitutive parameters of the presented structures, this work paves the way toward realization of non-closed acoustic devices, which could find applications in airborne sound manipulation and underwater demands.
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8
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Xu S, Dong FY, Guo WR, Han DD, Qian C, Gao F, Su WM, Chen H, Sun HB. Cross-wavelength invisibility integrated with various invisibility tactics. SCIENCE ADVANCES 2020; 6:6/39/eabb3755. [PMID: 32967829 PMCID: PMC7531887 DOI: 10.1126/sciadv.abb3755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 08/04/2020] [Indexed: 06/11/2023]
Abstract
As a superior self-protection strategy, invisibility has been a topic of long-standing interest in both academia and industry, because of its potential for intriguing applications that have only appeared thus far in science fiction. However, due to the strong dispersion of passive materials, achieving cross-wavelength invisibility remains an open challenge. Inspired by the natural ecological relationship between transparent midwater oceanic animals and the cross-wavelength detection strategy of their predators, we propose a cross-wavelength invisibility concept that integrates various invisibility tactics, where a Boolean metamaterial design procedure is presented to balance divergent material requirements over cross-scale wavelengths. As proof of concept, we experimentally demonstrate longwave cloaking and shortwave transparency simultaneously through a nanoimprinting technique. Our work extends the concept of stealth techniques from individual invisibility tactics targeting a single-wavelength spectrum to an integrated invisibility tactic targeting a cross-wavelength applications and may pave the way for development of cross-wavelength integrated metadevices.
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Affiliation(s)
- Su Xu
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China.
| | - Fu-Yan Dong
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Wen-Rui Guo
- Printable Electronics Research Centre, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Dong-Dong Han
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Chao Qian
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, The Electromagnetics Academy, College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Fei Gao
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, The Electromagnetics Academy, College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Wen-Ming Su
- Printable Electronics Research Centre, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Hongsheng Chen
- Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China.
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, The Electromagnetics Academy, College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Hong-Bo Sun
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China.
- State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Haidian, Beijing 100084, China
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9
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Eskandari H, Tyc T. Controlling refractive index of transformation-optics devices via optical path rescaling. Sci Rep 2019; 9:18412. [PMID: 31804518 PMCID: PMC6895162 DOI: 10.1038/s41598-019-54516-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 11/15/2019] [Indexed: 11/15/2022] Open
Abstract
We present a general method of designing optical devices based on optical conformal mapping and rescaling the optical path along a given bunch of rays. It provides devices with the same functionality as those based purely on conformal mapping, but enables to manipulate the refractive index to a great extent—for instance, eliminate superluminal regions of space as well as reduce the refractive index in other regions significantly. The method is illustrated in two examples, a waveguide coupler and a plasmonic bump cloak, and numerical simulations confirm its functionality.
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Affiliation(s)
- Hossein Eskandari
- Department of Electrical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
| | - Tomáš Tyc
- Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlářská 2, 61137, Brno, Czechia
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10
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Abstract
An invisibility cloak should completely hide an object from an observer, ideally across the visible spectrum and for all angles of incidence and polarizations of light, in three dimensions. However, until now, all such devices have been limited to either small bandwidths or have disregarded the phase of the impinging wave or worked only along specific directions. Here, we show that these seemingly fundamental restrictions can be lifted by using cloaks made of fast-light media, termed tachyonic cloaks, where the wave group velocity is larger than the speed of light in vacuum. On the basis of exact analytic calculations and full-wave causal simulations, we demonstrate three-dimensional cloaking that cannot be detected even interferometrically across the entire visible regime. Our results open the road for ultrabroadband invisibility of large objects, with direct implications for stealth and information technology, non-disturbing sensors, near-field scanning optical microscopy imaging, and superluminal propagation. Three-dimensional invisibility cloaks are either limited in bandwidth or disregard the phase of the impinging wave or work only in specific directions. Here, the authors report that these restrictions can be lifted by using cloaks made of fast-light media where the wave group velocity is larger than the speed of light in vacuum.
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11
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Li J, Yang R. Reconfigurable free-form graphene camouflage metasurfaces. OPTICS LETTERS 2018; 43:4631-4634. [PMID: 30272700 DOI: 10.1364/ol.43.004631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 08/26/2018] [Indexed: 06/08/2023]
Abstract
Becoming invisible is basically playing with the reflection spectra, where we can either rebuild the original propagating ray traces to cloak an object as if it never existed, or alternatively, conceal the reflected beams by perfectly absorbing all the incidences. In this Letter, a graphene based camouflage metasurface is proposed to carpet the randomly distributed metallic blocks on the ground. We show that the reflected traces could be reconstructed efficiently into the desired directions from any shape of graphene based metasurface simply by tuning the Fermi energy of the graphene patches. Meanwhile, the intensity of the reflections can also be disguised into the background spectra with the consideration of the inevitable reduced energy reflecting from the ground with lossy compositions or disordered scattering fields from uneven surfaces. Our approach of designing the graphene based metasurface coating is versatile for reconfigurable free-form camouflage under illumination from different incident angles and also demonstrates the possibility of creating diffuse reflections to escape detection.
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12
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Wang C, Yang Y, Liu Q, Liang D, Zheng B, Chen H, Xu Z, Wang H. Multi-frequency metasurface carpet cloaks. OPTICS EXPRESS 2018; 26:14123-14131. [PMID: 29877455 DOI: 10.1364/oe.26.014123] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Metasurfaces provide an alternative way to design three-dimensional arbitrary-shaped carpet cloaks with ultrathin thicknesses. Nevertheless, the previous metasurface carpet cloaks work only at a single frequency. To overcome this challenge, we here propose a macroscopic metasurface carpet cloak. The cloak is designed with a metasurface of a few layers that exhibit a special spatial distribution of the conductance and inductance in the unit cell; therefore, it can fully control the reflection phases at several independent frequencies simultaneously. Because of this, the present metasurface cloak can work at dual frequencies based on multi-resonance principle. The proposed design methodology will be very useful in future broadband macroscopic cloaks design with low profiles, light weights, and easy access.
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13
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Design and demonstration of an underwater acoustic carpet cloak. Sci Rep 2017; 7:705. [PMID: 28386065 PMCID: PMC5429626 DOI: 10.1038/s41598-017-00779-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 03/13/2017] [Indexed: 11/30/2022] Open
Abstract
The carpet cloak, which is designed to hide the objects placed on a reflecting surface, has become a topic of considerable interest. Inspired by those theoretical works, the experimental realization of acoustic carpet cloak in air host has been reported. However, due to the difficulty in obtaining the unit cell in reality, the underwater carpet cloak still remains in simulation thus far. Here, we design and fabricate a realizable underwater acoustic carpet cloak. By introducing a scaling factor, the structure of the carpet cloak, which is comprised of layered brass plates, is greatly simplified at the cost of some impedance match. The experimental results demonstrate a good performance of the proposed carpet cloak in a wide frequency range. Our work paves the way for future applications in the practical underwater devices.
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14
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Kim Y, Seo I, Koh IS, Lee Y. Design method for broadband free-space electromagnetic cloak based on isotropic material for size reduction and enhanced invisibility. OPTICS EXPRESS 2016; 24:22708-22717. [PMID: 27828340 DOI: 10.1364/oe.24.022708] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A design method is proposed that not only improves the invisibility of but also minimizes the size of a two-dimensional (2D) free-space electromagnetic cloak based on the quasi-conformal mapping (QCM) technique. The refractive index profile of the cloak based on the QCM is optimally scaled to minimize performance deterioration due to the imperfect isotropy of the cloak medium. Moreover, the method can be applied to compensate for the performance degradation due to size reduction. Based on the proposed method, as much as a 78.3% reduction in size is demonstrated. Enhancement of invisibility is evidenced by a 71% reduction in the normalized scattering cross section (SCS) at 10 GHz. Performance enhancement and miniaturization are achieved simultaneously with the extremely simple proposed method, making it one of the most practical cloaks reported thus far. Finally, experimental results over a broad bandwidth as well as for a wide range of incident angles are provided for cloaks fabricated using a 3D printer, which validate the effectiveness of the proposed method of cloak design.
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15
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Yang Y, Jing L, Zheng B, Hao R, Yin W, Li E, Soukoulis CM, Chen H. Full-Polarization 3D Metasurface Cloak with Preserved Amplitude and Phase. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:6866-71. [PMID: 27218885 DOI: 10.1002/adma.201600625] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 04/12/2016] [Indexed: 05/14/2023]
Abstract
A full-polarization arbitrary-shaped 3D metasurface cloak with preserved amplitude and phase in microwave frequencies is experimentally demonstrated. By taking the unique feature of metasurfaces, it is shown that the cloak can completely restore the polarization, amplitude, and phase of light for full polarization as if light was incident on a flat mirror.
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Affiliation(s)
- Yihao Yang
- State Key Laboratory of Modern Optical Instrumentation, The Electromagnetics Academy, Zhejiang University, Hangzhou, 310027, P. R. China
- College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, IA, 50011, USA
| | - Liqiao Jing
- State Key Laboratory of Modern Optical Instrumentation, The Electromagnetics Academy, Zhejiang University, Hangzhou, 310027, P. R. China
- College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Bin Zheng
- State Key Laboratory of Modern Optical Instrumentation, The Electromagnetics Academy, Zhejiang University, Hangzhou, 310027, P. R. China
- College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Ran Hao
- College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Wenyan Yin
- College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Erping Li
- College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Costas M Soukoulis
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, IA, 50011, USA
| | - Hongsheng Chen
- State Key Laboratory of Modern Optical Instrumentation, The Electromagnetics Academy, Zhejiang University, Hangzhou, 310027, P. R. China
- College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
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16
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Tyc T, Oxburgh S, Cowie EN, Chaplain GJ, Macauley G, White CD, Courtial J. Omnidirectional transformation-optics cloak made from lenses and glenses. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2016; 33:1032-1040. [PMID: 27409429 DOI: 10.1364/josaa.33.001032] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present a design for an omnidirectional transformation-optics (TO) cloak comprising thin lenses and glenses (generalized thin lenses) [J. Opt. Soc. Am. A33, 962 (2016)1084-7529JOAOD610.1364/JOSAA.33.000962]. It should be possible to realize such devices in pixelated form. Our design is a piecewise nonaffine generalization of piecewise affine pixelated-TO devices [Proc. SPIE9193, 91931E (2014)PSISDG0277-786X10.1117/12.2061404; J. Opt18, 044009 (2016)]. It is intended to be a step in the direction of TO devices made entirely from lenses, which should be readily realizable on large length scales and for a broad range of wavelengths.
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17
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Yang Y, Wang H, Yu F, Xu Z, Chen H. A metasurface carpet cloak for electromagnetic, acoustic and water waves. Sci Rep 2016; 6:20219. [PMID: 26822429 PMCID: PMC4731745 DOI: 10.1038/srep20219] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Accepted: 12/23/2015] [Indexed: 02/02/2023] Open
Abstract
We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak.
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Affiliation(s)
- Yihao Yang
- State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
| | - Huaping Wang
- Ocean College, Zhejiang University, Hangzhou 310058, China
| | - Faxin Yu
- School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China
| | - Zhiwei Xu
- Ocean College, Zhejiang University, Hangzhou 310058, China
| | - Hongsheng Chen
- State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
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18
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Ma HF, Wang GZ, Jiang WX, Cui TJ. Independent control of differently-polarized waves using anisotropic gradient-index metamaterials. Sci Rep 2014; 4:6337. [PMID: 25231412 PMCID: PMC4166714 DOI: 10.1038/srep06337] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 08/20/2014] [Indexed: 11/13/2022] Open
Abstract
We propose a kind of anisotropic gradient-index (GRIN) metamaterials, which can be used to control differently-polarized waves independently. We show that two three- dimensional (3D) planar lenses made of such anisotropic GRIN metamaterials are able to make arbitrary beam deflections for the vertical (or horizontal) polarization but have no response to the horizontal (or vertical) polarization. Then the vertically- and horizontally-polarized waves are separated and controlled independently to deflect to arbitrarily different directions by designing the anisotropic GRIN planar lenses. We make experimental verifications of the lenses using such a special metamaterial, which has both electric and magnetic responses simultaneously to reach approximately equal permittivity and permeability. Hence excellent impedance matching is obtained between the GRIN planar lenses and the air. The measurement results demonstrate good performance on the independent controls of differently-polarized waves, as observed in the numerical simulations.
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Affiliation(s)
- Hui Feng Ma
- State Key Laboratory of Millimeter Waves, School of Information Science and Engineering, Southeast University, Nanjing 210096, China
| | - Gui Zhen Wang
- State Key Laboratory of Millimeter Waves, School of Information Science and Engineering, Southeast University, Nanjing 210096, China
| | - Wei Xiang Jiang
- State Key Laboratory of Millimeter Waves, School of Information Science and Engineering, Southeast University, Nanjing 210096, China
| | - Tie Jun Cui
- State Key Laboratory of Millimeter Waves, School of Information Science and Engineering, Southeast University, Nanjing 210096, China
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19
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Xu H, Shi X, Gao F, Sun H, Zhang B. Ultrathin three-dimensional thermal cloak. PHYSICAL REVIEW LETTERS 2014; 112:054301. [PMID: 24580599 DOI: 10.1103/physrevlett.112.054301] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Indexed: 05/27/2023]
Abstract
We report the first experimental realization of a three-dimensional thermal cloak shielding an air bubble in a bulk metal without disturbing the external conductive thermal flux. The cloak is made of a thin layer of homogeneous and isotropic material with specially designed three-dimensional manufacturing. The cloak's thickness is 100 μm while the cloaked air bubble has a diameter of 1 cm, achieving the ratio between dimensions of the cloak and the cloaked object 2 orders smaller than previous thermal cloaks, which were mainly realized in a two-dimensional geometry. This work can find applications in novel thermal devices in the three-dimensional physical space.
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Affiliation(s)
- Hongyi Xu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Xihang Shi
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Fei Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Handong Sun
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore and Centre for Disruptive Photonic Technologies, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Baile Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore and Centre for Disruptive Photonic Technologies, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
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20
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Zang X, Li Z, Shi C, Chen L, Cai B, Zhu Y, Li L, Wang X. Rotatable illusion media for manipulating terahertz electromagnetic waves. OPTICS EXPRESS 2013; 21:25565-25572. [PMID: 24150396 DOI: 10.1364/oe.21.025565] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Based on composite optical transformation, we propose a rotatable illusion media with positive permittivity and permeability to manipulate terahertz waves, and a new way to realize singular parameter-independent cloaks when the incident wave with a certain width propagates from specific incident directions. The fundamental mechanism of this kind of cloak is that the illusion media can be able to avoid the incident wave interacting with the objects. Comparing with traditional transformation-coordinate-based cloaks such as cylindrical-shaped cloaks, our cloaks are independent of singular material parameters. Furthermore, this type of rotatable illusion media can be applied to design tunable miniaturized high-directivity antenna (a small antenna array covered with the rotatable illusion media appears like a large one and meanwhile, the radiation directions of the small antenna array is tunable via this rotatable illusion media). Full wave simulations are performed to confirm these points.
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21
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Homogeneous thermal cloak with constant conductivity and tunable heat localization. Sci Rep 2013; 3:1593. [PMID: 23549139 PMCID: PMC3615408 DOI: 10.1038/srep01593] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 03/19/2013] [Indexed: 11/08/2022] Open
Abstract
Invisible cloak has long captivated the popular conjecture and attracted intensive research in various communities of wave dynamics, e.g., optics, electromagnetics, acoustics, etc. However, their inhomogeneous and extreme parameters imposed by transformation-optic method will usually require challenging realization with metamaterials, resulting in narrow bandwidth, loss, polarization-dependence, etc. In this paper, we demonstrate that thermodynamic cloak can be achieved with homogeneous and finite conductivity only employing naturally available materials. It is demonstrated that the thermal localization inside the coating layer can be tuned and controlled robustly by anisotropy, which enables an incomplete cloak to function perfectly. Practical realization of such homogeneous thermal cloak has been suggested by using two naturally occurring conductive materials, which provides an unprecedentedly plausible way to flexibly realize thermal cloak and manipulate heat flow with phonons.
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22
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Luo Y, Zhang B, Han T, Chen Z, Duan Y, Chu CW, Barbastathis G, Qiu CW. Phase-preserved optical elevator. OPTICS EXPRESS 2013; 21:6650-7. [PMID: 23546046 PMCID: PMC3635697 DOI: 10.1364/oe.21.006650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 01/23/2013] [Accepted: 01/29/2013] [Indexed: 06/02/2023]
Abstract
The unique superiority of transformation optics devices designed from coordinate transformation is their capability of recovering both ray trajectory and optical path length in light manipulation. However, very few experiments have been done so far to verify this dual-recovery property from viewpoints of both ray trajectory and optical path length simultaneously. The experimental difficulties arise from the fact that most previous optical transformation optics devices only work at the nano-scale; the lack of intercomparison between data from both optical path length and ray trajectory measurement in these experiments obscured the fact that the ray path was subject to a subwavelength lateral shift that was otherwise not easily perceivable and, instead, was pointed out theoretically [B. Zhang et al. Phys. Rev. Lett. 104, 233903, 2010]. Here, we use a simple macroscopic transformation optics device of phase-preserved optical elevator, which is a typical birefringent optical phenomenon that can virtually lift an optical image by a macroscopic distance, to demonstrate decisively the unique optical path length preservation property of transformation optics. The recovery of ray trajectory is first determined with no lateral shift in the reflected ray. The phase preservation is then verified with incoherent white-light interferometry without ambiguity and phase unwrapping.
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Affiliation(s)
- Yuan Luo
- Center for Optoelectronic Biomedicine, College of Medicine, National Taiwan University, Taipei 10051,
Taiwan
- Molecular Imaging Center, National Taiwan University, Taipei 10617,
Taiwan
| | - Baile Zhang
- Division of Physics and Applied Physics, Nanyang Technological University, Singapore 637371,
Singapore
- Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371,
Singapore
| | - Tiancheng Han
- School of Physical Science and Technology, Southwest University, Chongqing 400715,
China
| | - Zhi Chen
- Singapore-MIT Alliance for Research and Technology (SMART) Centre, Singapore 117576,
Singapore
- Department of Bioengineering, National University of Singapore, Singapore 119620,
Singapore
| | - Yubo Duan
- Singapore-MIT Alliance for Research and Technology (SMART) Centre, Singapore 117576,
Singapore
- Department of Bioengineering, National University of Singapore, Singapore 119620,
Singapore
| | - Chia-Wei Chu
- Center for Optoelectronic Biomedicine, College of Medicine, National Taiwan University, Taipei 10051,
Taiwan
- Molecular Imaging Center, National Taiwan University, Taipei 10617,
Taiwan
| | - George Barbastathis
- School of Physical Science and Technology, Southwest University, Chongqing 400715,
China
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
USA
| | - Cheng Wei Qiu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 119620,
Singapore
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23
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Gao D, Qiu CW, Gao L, Cui T, Zhang S. Macroscopic broadband optical escalator with force-loaded transformation optics. OPTICS EXPRESS 2013; 21:796-803. [PMID: 23388972 DOI: 10.1364/oe.21.000796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Transformation optics enables one to guide and control light at will using metamaterials. However the designed device is deterministic and not flexible for different objects. Based on force-loaded transformation optics we propose a force-induced transformational device, which can realize dynamic escalator metamorphosing continuously between optical elevator and invisibility cloak. This escalator can visually lift up and down the perceived height of a plane fixed in space by controlling the forces loaded in different directions. Or conversely, the escalator can physically lift up and down a plane while visually maintaining the same height to an outside observer. One can quickly adjust this device to the required demand without changing the background index, while the usual transformation cloak will be detectable due to the lateral shift from mismatched background. The schematic is self-adaptive, multi-functional, and free of metamaterial or nanofabrication. Our work opens a new perspective in controlling light dynamically and continuously, empowering unprecedented applications in military cloak, optic communication, holographic imaging, and phase-involved microtechnique.
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Affiliation(s)
- Dongliang Gao
- Department of Electrical and Computer Engineering, National University of Singapore, Republic of Singapore
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24
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Landy N, Smith DR. A full-parameter unidirectional metamaterial cloak for microwaves. NATURE MATERIALS 2013; 12:25-28. [PMID: 23142840 DOI: 10.1038/nmat3476] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 10/04/2012] [Indexed: 05/27/2023]
Abstract
Invisibility is a notion that has long captivated the popular imagination. However, in 2006, invisibility became a practical matter for the scientific community as well, with the suggestion that artificially structured metamaterials could enable a new electromagnetic design paradigm, now termed transformation optics. Since the advent of transformation optics and subsequent initial demonstration of the microwave cloak, the field has grown rapidly. However, the complexity of the transformation optics material prescription has continually forced researchers to make simplifying approximations to achieve even a subset of the desired functionality. These approximations place profound limitations on the performance of transformation optics devices in general, and cloaks especially. Here, we design and experimentally characterize a two-dimensional, unidirectional cloak that makes no approximations to the underlying transformation optics formulation, yet is capable of reducing the scattering of an object ten wavelengths in size. We demonstrate that this approximation-free design regains the performance characteristics promised by transformation optics.
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Affiliation(s)
- Nathan Landy
- Center for Metamaterials and Integrated Plasmonics, Department of Electrical and Computer Engineering, Pratt School of Engineering, Duke University, Box 90291, Durham, North Carolina 27708, USA.
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25
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Radiation-suppressed plasmonic open resonators designed by nonmagnetic transformation optics. Sci Rep 2012; 2:784. [PMID: 23136641 PMCID: PMC3491667 DOI: 10.1038/srep00784] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 09/17/2012] [Indexed: 11/30/2022] Open
Abstract
How to confine light energy associated with surface plasmon polaritons (SPPs) in a physical space with minimal radiation loss whereas creating maximum interacting section with surrounding environment is of particular interest in plasmonic optics. By virtue of transformation optics, we propose a design method of forming a polygonal surface-plasmonic resonator in fully open structures by applying the nonmagnetic affine transformation optics strategy. The radiation loss can be suppressed because SPPs that propagate in the designed open structures will be deceived as if they were propagating on a flat metal/dielectric interface without radiation. Because of the nonmagnetic nature of the transformation strategy, this design can be implemented with dielectric materials available in nature. An experimentally verifiable model is subsequently proposed for future experimental demonstration. Our design may find potential applications in omnidirectional sensing, light harvesting, energy storage and plasmonic lasing.
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26
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Abstract
Within the past a few years, transformation optics has emerged as a new research area, since it provides a general methodology and design tool for manipulating electromagnetic waves in a prescribed manner. Using transformation optics, researchers have demonstrated a host of striking phenomena and devices; many of which were only thought possible in science fiction. In this paper, we review the most recent advances in transformation optics. We focus on the theory, design, fabrication and characterization of transformation devices such as the carpet cloak, "Janus" lens and plasmonic cloak at optical frequencies, which allow routing light at the nanoscale. We also provide an outlook of the challenges and future directions in this fascinating area of transformation optics.
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Affiliation(s)
- Yongmin Liu
- NSF Nanoscale Science and Engineering Center-NSEC, 3112 Etcheverry Hall, University of California, Berkeley, CA 94720, USA
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27
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Zhang J, Liu L, Luo Y, Zhang S, Mortensen NA. Homogeneous optical cloak constructed with uniform layered structures. OPTICS EXPRESS 2011; 19:8625-8631. [PMID: 21643114 DOI: 10.1364/oe.19.008625] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The prospect of rendering objects invisible has intrigued researchers for centuries. Transformation optics based invisibility cloak design is now bringing this goal from science fictions to reality and has already been demonstrated experimentally in microwave and optical frequencies. However, the majority of the invisibility cloaks reported so far have a spatially varying refractive index which requires complicated design processes. Besides, the size of the hidden object is usually small relative to that of the cloak device. Here we report the experimental realization of a homogenous invisibility cloak with a uniform silicon grating structure. The design strategy eliminates the need for spatial variation of the material index, and in terms of size it allows for a very large obstacle/cloak ratio. A broadband invisibility behavior has been verified at near-infrared frequencies, opening up new opportunities for using uniform layered medium to realize invisibility at any frequency ranges, where high-quality dielectrics are available.
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Affiliation(s)
- Jingjing Zhang
- DTU Fotonik-Department of Photonics Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
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28
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Halimeh JC, Schmied R, Wegener M. Newtonian photorealistic ray tracing of grating cloaks and correlation-function-based cloaking-quality assessment. OPTICS EXPRESS 2011; 19:6078-6092. [PMID: 21451631 DOI: 10.1364/oe.19.006078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Grating cloaks are a variation of dielectric carpet (or ground-plane) cloaks. The latter were introduced by Li and Pendry. In contrast to the numerical work involved in the quasi-conformal carpet cloak, the refractive-index profile of a conformal grating cloak follows a closed and exact analytical form. We have previously mentioned that finite-size conformal grating cloaks may exhibit better cloaking than usual finite-size carpet cloaks. In this paper, we directly visualize their performance using photorealistic ray-tracing simulations. We employ a Newtonian approach that is advantageous compared to conventional ray tracing based on Snell's law. Furthermore, we quantify the achieved cloaking quality by computing the cross-correlations of rendered images. The cross-correlations for the grating cloak are much closer to 100% (i.e., ideal) than those for the Gaussian carpet cloak.
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Affiliation(s)
- Jad C Halimeh
- Physics Department, Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, München, Germany
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29
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Abstract
Invisibility cloaks, which used to be confined to the realm of fiction, have now been turned into a scientific reality thanks to the enabling theoretical tools of transformation optics and conformal mapping. Inspired by those theoretical works, the experimental realization of electromagnetic invisibility cloaks has been reported at various electromagnetic frequencies. All the invisibility cloaks demonstrated thus far, however, have relied on nano- or micro-fabricated artificial composite materials with spatially varying electromagnetic properties, which limit the size of the cloaked region to a few wavelengths. Here, we report the first realization of a macroscopic volumetric invisibility cloak constructed from natural birefringent crystals. The cloak operates at visible frequencies and is capable of hiding, for a specific light polarization, three-dimensional objects of the scale of centimetres and millimetres. Our work opens avenues for future applications with macroscopic cloaking devices. Until now, invisibility cloaks have only covered a region of a few wavelengths because of their nanostructured materials. Chen et al. describe a macroscopic cloak, made of calcite birefringent crystals, which works for a specific polarization at visible wavelengths.
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30
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Zhang B, Luo Y, Liu X, Barbastathis G. Macroscopic invisibility cloak for visible light. PHYSICAL REVIEW LETTERS 2011; 106:033901. [PMID: 21405275 DOI: 10.1103/physrevlett.106.033901] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Indexed: 05/15/2023]
Abstract
Invisibility cloaks, a subject that usually occurs in science fiction and myths, have attracted wide interest recently because of their possible realization. The biggest challenge to true invisibility is known to be the cloaking of a macroscopic object in the broad range of wavelengths visible to the human eye. Here we experimentally solve this problem by incorporating the principle of transformation optics into a conventional optical lens fabrication with low-cost materials and simple manufacturing techniques. A transparent cloak made of two pieces of calcite is created. This cloak is able to conceal a macroscopic object with a maximum height of 2 mm, larger than 3500 free-space-wavelength, inside a transparent liquid environment. Its working bandwidth encompassing red, green, and blue light is also demonstrated.
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Affiliation(s)
- Baile Zhang
- Singapore-MIT Alliance for Research and Technology Centre, Singapore 117543, Singapore
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31
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Xu X, Feng Y, Yu Z, Jiang T, Zhao J. Simplified ground plane invisibility cloak by multilayer dielectrics. OPTICS EXPRESS 2010; 18:24477-24485. [PMID: 21164794 DOI: 10.1364/oe.18.024477] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Most implementations of the ground plane invisibility cloak are based on the isotropic design through the quasi-conformal transformation. However recent theoretical analysis predicts the unavoidable lateral shift of the scattering fields associated with these cloaks making them detectable. In this paper, we propose an alternative method to design the ground plane invisibility clock with electromagnetic beam modulation blocks through simple coordinate transformation discussed in our previous work. The ground plane cloak obtained with the rigorous transformation optics possesses moderate anisotropic distributions of material parameters, but results in no lateral shift of the scattering fields. To realize the design, a possible scheme is suggested by discretizing the ground plane cloak to several homogeneous sub-blocks. These sub-blocks can be realized with multilayer isotropic dielectrics with alignment angles that are determined by the effective medium theory. Thus the non-magnetic ground plane invisibility cloak can be constructed by several multilayered normal dielectrics aligned in different angles. The performance of the proposed cloak and its practical implementation is validated by full-wave electromagnetic simulations with both near field distributions and far field scattering patterns under different EM wave incident angles. The proposed cloak is composed of normal dielectric multilayers, thus can leads to easy experimental demonstration of non-magnetic ground plane cloak in the frequency range from microwave to optical.
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Affiliation(s)
- Xiaofei Xu
- Department of Electronic Engineering, School of Electronic Science and Engineering, Nanjing Univeristy, Nanjing, 210093, China
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32
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Schmied R, Halimeh JC, Wegener M. Conformal carpet and grating cloaks. OPTICS EXPRESS 2010; 18:24361-24367. [PMID: 21164783 DOI: 10.1364/oe.18.024361] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We introduce a class of conformal versions of the previously introduced quasi-conformal carpet cloak, and show how to construct such conformal cloaks for different cloak shapes. Our method provides exact refractive-index profiles in closed mathematical form for the usual carpet cloak as well as for other shapes. By analyzing their asymptotic behavior, we find that the performance of finite-size cloaks becomes much better for metal shapes with zero average value, e.g., for gratings.
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33
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Landy NI, Kundtz N, Smith DR. Designing three-dimensional transformation optical media using quasiconformal coordinate transformations. PHYSICAL REVIEW LETTERS 2010; 105:193902. [PMID: 21231170 DOI: 10.1103/physrevlett.105.193902] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Revised: 09/29/2010] [Indexed: 05/30/2023]
Abstract
We introduce an approach to the design of three-dimensional transformation optical (TO) media based on a generalized quasiconformal mapping approach. The generalized quasiconformal TO (QCTO) approach enables the design of media that can, in principle, be broadband and low loss, while controlling the propagation of waves with arbitrary angles of incidence and polarization. We illustrate the method in the design of a three-dimensional carpet ground plane cloak and of a flattened Luneburg lens. Ray-trace studies provide a confirmation of the performance of the QCTO media, while also revealing the limited performance of index-only versions of these devices.
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Affiliation(s)
- N I Landy
- Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, USA
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34
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Ergin T, Halimeh JC, Stenger N, Wegener M. Optical microscopy of 3D carpet cloaks:ray-tracing calculations. OPTICS EXPRESS 2010; 18:20535-20545. [PMID: 20940947 DOI: 10.1364/oe.18.020535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In a recent publication (T. Ergin et al., Science 328, 337 (2010)), three-dimensional broadband dielectric carpet cloaks have been fabricated and experimentally characterized by optical bright-field and dark-field microscopy using unpolarized light from an incandescent lamp. A direct comparison with theory has not been provided so far. In the present work, we treat the carpet cloak as well as the entire optical microscope within the ray-optics approximation and the cloak within the effective-medium approximation. We find good qualitative agreement between experimental results and our calculations.
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Affiliation(s)
- Tolga Ergin
- Institut für Angewandte Physik and DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.
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35
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Abstract
Carpet cloaking is proposed to hide an object on a dielectric half-space from electromagnetic (EM) detection. A two-dimensional conformal transformation specified by an analytic function is utilized for the design. Only one nonsingular material parameter distribution suffices for the characterization. The cloaking cover situates on the dielectric half-space, and consists of a lossless upper part for EM wave redirection and an absorbing bottom layer for inducing correct reflection coefficient and absorbing transmission. Numerical simulations with Gaussian beam incidence are performed for verification. The broadband behavior of the carpet cloaking is also illustrated.
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Affiliation(s)
- Pu Zhang
- JORCEP (KTH-ZJU Joint Center of Photonics), Centre for Optical and Electromagnetic Research, East Building #5, Zijingang campus, Zhejiang University (ZJU), Hangzhou 310058, China
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