1
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Wen X, Cho C, Zhu X, Park N, Li J. Nonreciprocal field transformation with active acoustic metasurfaces. SCIENCE ADVANCES 2024; 10:eadm9673. [PMID: 38820157 PMCID: PMC11141624 DOI: 10.1126/sciadv.adm9673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 04/30/2024] [Indexed: 06/02/2024]
Abstract
Field transformation, as an extension of the transformation optics, provides a unique means for nonreciprocal wave manipulation, while the experimental realization remains a substantial challenge as it requires stringent material parameters of the metamaterials, e.g., purely nonreciprocal bianisotropic parameters. Here, we develop and demonstrate a nonreciprocal field transformation in a two-dimensional acoustic system, using an active metasurface that can independently control all constitutive parameters and achieve purely nonreciprocal Willis coupling. The field-transforming metasurface enables tailor-made field distribution manipulation, achieving localized field amplification by a predetermined ratio. The metasurface demonstrates the self-adaptive capability to various excitation conditions and can be extended to other geometric shapes. The metasurface also achieves nonreciprocal wave propagation for internal and external excitations, demonstrating a one-way acoustic device. The nonreciprocal field transformation not only extends the framework of the transformation theory for nonreciprocal wave manipulation but also holds great potential in applications such as ultrasensitive sensors and nonreciprocal communication.
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Affiliation(s)
- Xinhua Wen
- Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
| | - Choonlae Cho
- Photonic Systems Laboratory, Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, South Korea
| | - Xinghong Zhu
- Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
| | - Namkyoo Park
- Photonic Systems Laboratory, Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, South Korea
| | - Jensen Li
- Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
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2
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Yang Y, Yang B, Ma G, Li J, Zhang S, Chan CT. Non-Abelian physics in light and sound. Science 2024; 383:eadf9621. [PMID: 38386745 DOI: 10.1126/science.adf9621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 01/17/2024] [Indexed: 02/24/2024]
Abstract
Non-Abelian phenomena arise when the sequence of operations on physical systems influences their behaviors. By possessing internal degrees of freedom such as polarization, light and sound can be subjected to various manipulations, including constituent materials, structured environments, and tailored source conditions. These manipulations enable the creation of a great variety of Hamiltonians, through which rich non-Abelian phenomena can be explored and observed. Recent developments have constituted a versatile testbed for exploring non-Abelian physics at the intersection of atomic, molecular, and optical physics; condensed matter physics; and mathematical physics. These fundamental endeavors could enable photonic and acoustic devices with multiplexing functionalities. Our review aims to provide a timely and comprehensive account of this emerging topic. Starting from the foundation of matrix-valued geometric phases, we address non-Abelian topological charges, non-Abelian gauge fields, non-Abelian braiding, non-Hermitian non-Abelian phenomena, and their realizations with photonics and acoustics and conclude with future prospects.
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Affiliation(s)
- Yi Yang
- Department of Physics, The University of Hong Kong, Pokfulam, Hong Kong, China
- HK Institute of Quantum Science and Technology, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Biao Yang
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China
- Hunan Provincial Key Laboratory of Novel Nano-Optoelectronic Information Materials and Devices, National University of Defense Technology, Changsha, China
- Nanhu Laser Laboratory, National University of Defense Technology, Changsha, China
| | - Guancong Ma
- Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China
| | - Jensen Li
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Shuang Zhang
- Department of Physics, The University of Hong Kong, Pokfulam, Hong Kong, China
- HK Institute of Quantum Science and Technology, The University of Hong Kong, Pokfulam, Hong Kong, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China
- New Cornerstone Science Laboratory, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - C T Chan
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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3
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Cui X, Zhang RY, Zhang ZQ, Chan CT. Photonic Z_{2} Topological Anderson Insulators. PHYSICAL REVIEW LETTERS 2022; 129:043902. [PMID: 35939009 DOI: 10.1103/physrevlett.129.043902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 06/28/2022] [Indexed: 06/15/2023]
Abstract
That disorder can induce nontrivial topology is a surprising discovery in topological physics. As a typical example, Chern topological Anderson insulators (TAIs) have been realized in photonic systems, where the topological phases exist without symmetry protection. In this Letter, by taking transverse magnetic and transverse electric polarizations as pseudospin degrees of freedom, we theoretically propose a scheme to realize disorder-induced symmetry-protected topological phase transitions in two-dimensional photonic crystals with a combined time-reversal, mirror, and duality symmetry T_{f}=TM_{z}D. In particular, we demonstrate that the disorder-induced symmetry-protected topological phase persists even without pseudospin conservation, thereby realizing a photonic Z_{2} TAI, in contrast to a Z-classified quantum spin Hall (QSH) TAI with decoupled spins. By formulating a new scattering approach, we show that the topology of both the QSH and Z_{2} TAIs can be manifested by the accumulated spin rotations of the reflected waves from the photonic crystals. Using a transmission structure, we also illustrate the trivialization of a disordered QSH phase with an even integer topological index caused by spin coupling.
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Affiliation(s)
- Xiaohan Cui
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Ruo-Yang Zhang
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Zhao-Qing Zhang
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
| | - C T Chan
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
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4
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Biegańska D, Pieczarka M, Estrecho E, Steger M, Snoke DW, West K, Pfeiffer LN, Syperek M, Truscott AG, Ostrovskaya EA. Collective Excitations of Exciton-Polariton Condensates in a Synthetic Gauge Field. PHYSICAL REVIEW LETTERS 2021; 127:185301. [PMID: 34767383 DOI: 10.1103/physrevlett.127.185301] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 07/24/2021] [Accepted: 09/21/2021] [Indexed: 06/13/2023]
Abstract
Collective (elementary) excitations of quantum bosonic condensates, including condensates of exciton polaritons in semiconductor microcavities, are a sensitive probe of interparticle interactions. In anisotropic microcavities with momentum-dependent transverse-electric-transverse-magnetic splitting of the optical modes, the excitations' dispersions are predicted to be strongly anisotropic, which is a consequence of the synthetic magnetic gauge field of the cavity, as well as the interplay between different interaction strengths for polaritons in the singlet and triplet spin configurations. Here, by directly measuring the dispersion of the collective excitations in a high-density optically trapped exciton-polariton condensate, we observe excellent agreement with the theoretical predictions for spinor polariton excitations. We extract the interaction constants for polaritons of the same and opposite spin and map out the characteristic spin textures in an interacting spinor condensate of exciton polaritons.
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Affiliation(s)
- D Biegańska
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies and Nonlinear Physics Centre, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - M Pieczarka
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies and Nonlinear Physics Centre, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - E Estrecho
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies and Nonlinear Physics Centre, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - M Steger
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - D W Snoke
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - K West
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - L N Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - M Syperek
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - A G Truscott
- Laser Physics Centre, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - E A Ostrovskaya
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies and Nonlinear Physics Centre, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
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5
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Wang W, Gao W, Chen X, Shi F, Li G, Dong J, Xiang Y, Zhang S. Moiré Fringe Induced Gauge Field in Photonics. PHYSICAL REVIEW LETTERS 2020; 125:203901. [PMID: 33258635 DOI: 10.1103/physrevlett.125.203901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Accepted: 10/23/2020] [Indexed: 06/12/2023]
Abstract
We realize moiré fringe induced gauge field in a double-layer photonic honeycomb metacrystal with mismatched lattice constants. Benefitting from the generated strong effective gauge field, we report direct measurement of the band diagrams of both Landau level flat bands and intermagnetic-domain edge states. Importantly, we observe the correlation between the momentum and orbital position of the Landau modes, serving as an evidence of the noncommuteness between orthogonal components of the momentum. Without complicated time driving mechanics and careful site-by-site engineering, moiré superlattices could emerge as a powerful means to generate effective gauge fields for photonics benefiting from its simplicity and reconfigurability, which can be applied to nonlinearity enhancement and lasing applications at optical frequencies.
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Affiliation(s)
- Wenhui Wang
- School of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Wenlong Gao
- School of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Xiaodong Chen
- School of Physics & State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China
| | - Fulong Shi
- School of Physics & State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China
| | - Guixin Li
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jianwen Dong
- School of Physics & State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China
| | - Yuanjiang Xiang
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Shuang Zhang
- School of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
- Department of Physics, University of Hong Kong, Hong Kong, China
- Department of Electrical & Electronic Engineering, University of Hong Kong, Hong Kong, China
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6
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Xiong Z, Zhang RY, Yu R, Chan CT, Chen Y. Hidden-symmetry-enforced nexus points of nodal lines in layer-stacked dielectric photonic crystals. LIGHT, SCIENCE & APPLICATIONS 2020; 9:176. [PMID: 33088493 PMCID: PMC7572392 DOI: 10.1038/s41377-020-00382-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 07/27/2020] [Accepted: 08/06/2020] [Indexed: 06/01/2023]
Abstract
It was recently demonstrated that the connectivities of bands emerging from zero frequency in dielectric photonic crystals are distinct from their electronic counterparts with the same space groups. We discover that in an AB-layer-stacked photonic crystal composed of anisotropic dielectrics, the unique photonic band connectivity leads to a new kind of symmetry-enforced triply degenerate points at the nexuses of two nodal rings and a Kramers-like nodal line. The emergence and intersection of the line nodes are guaranteed by a generalized 1/4-period screw rotation symmetry of Maxwell's equations. The bands with a constant k z and iso-frequency surfaces near a nexus point both disperse as a spin-1 Dirac-like cone, giving rise to exotic transport features of light at the nexus point. We show that spin-1 conical diffraction occurs at the nexus point, which can be used to manipulate the charges of optical vortices. Our work reveals that Maxwell's equations can have hidden symmetries induced by the fractional periodicity of the material tensor components and hence paves the way to finding novel topological nodal structures unique to photonic systems.
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Affiliation(s)
- Zhongfei Xiong
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, 430074 China
| | - Ruo-Yang Zhang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Rui Yu
- School of Physics and Technology, Wuhan University, Wuhan, 430072 China
| | - C. T. Chan
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Yuntian Chen
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, 430074 China
- Wuhan National Laboratory of Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074 China
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7
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Yang Y, Zhen B, Joannopoulos JD, Soljačić M. Non-Abelian generalizations of the Hofstadter model: spin-orbit-coupled butterfly pairs. LIGHT, SCIENCE & APPLICATIONS 2020; 9:177. [PMID: 33088494 PMCID: PMC7572376 DOI: 10.1038/s41377-020-00384-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 07/28/2020] [Accepted: 08/02/2020] [Indexed: 06/11/2023]
Abstract
The Hofstadter model, well known for its fractal butterfly spectrum, describes two-dimensional electrons under a perpendicular magnetic field, which gives rise to the integer quantum Hall effect. Inspired by the real-space building blocks of non-Abelian gauge fields from a recent experiment, we introduce and theoretically study two non-Abelian generalizations of the Hofstadter model. Each model describes two pairs of Hofstadter butterflies that are spin-orbit coupled. In contrast to the original Hofstadter model that can be equivalently studied in the Landau and symmetric gauges, the corresponding non-Abelian generalizations exhibit distinct spectra due to the non-commutativity of the gauge fields. We derive the genuine (necessary and sufficient) non-Abelian condition for the two models from the commutativity of their arbitrary loop operators. At zero energy, the models are gapless and host Weyl and Dirac points protected by internal and crystalline symmetries. Double (8-fold), triple (12-fold), and quadrupole (16-fold) Dirac points also emerge, especially under equal hopping phases of the non-Abelian potentials. At other fillings, the gapped phases of the models give rise to topological insulators. We conclude by discussing possible schemes for experimental realization of the models on photonic platforms.
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Affiliation(s)
- Yi Yang
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Bo Zhen
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - John D. Joannopoulos
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Marin Soljačić
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
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8
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Liu Y, Tang S, Shi H, Zhao J, Wang W, Zhou B. Dielectric approximation media to reproduce dispersion for field transformation. APPLIED OPTICS 2020; 59:7613-7620. [PMID: 32902461 DOI: 10.1364/ao.393136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 07/31/2020] [Indexed: 06/11/2023]
Abstract
Field transformation is complementary to transformation optics as it converts polarization without reflection for any incidence, despite not being impedance-matched to vacuum. However, to ease manufacture, a dielectric approximation may degrade the transmission performance due to the approximate dispersion relation for the exact reciprocal medium. In this paper, we instead propose a different dielectric equivalent medium to guarantee the exact dispersion. We also discuss the birefringence phenomenon in such dielectric media, and their unavoidable induced reflections.
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9
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Shi H, Xiong Z, Chen W, Xu J, Wang S, Chen Y. Gauge-field description of Sagnac frequency shift and mode hybridization in a rotating cavity. OPTICS EXPRESS 2019; 27:28114-28122. [PMID: 31684569 DOI: 10.1364/oe.27.028114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 08/16/2019] [Indexed: 06/10/2023]
Abstract
Active optical systems can give rise to intriguing phenomena and applications that are not available in conventional passive systems. Structural rotation has been widely employed to achieve non-reciprocity or time-reversal symmetry breaking. Here, we examine the quasi-normal modes and scattering properties of a dielectric disk under rotation. In addition to the familiar phenomenon of Sagnac frequency shift, we observe the the hybridization of the clockwise (CW) and counter-clockwise CCW) chiral modes of the cavity controlled by the rotation. The rotation tends to suppress one chiral mode while amplifying the other, and it leads to the variation of the far field. The phenomenon can be understood as the result of a synthetic gauge field induced by the rotation of the cavity. We explicitly derived this gauge field and the resulting Sagnac frequency shift. The analytical results are corroborated by finite element simulations. Our results can be applied in the measurement of rotating devices by probing the far field.
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10
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Chen Y, Zhang RY, Xiong Z, Hang ZH, Li J, Shen JQ, Chan CT. Non-Abelian gauge field optics. Nat Commun 2019; 10:3125. [PMID: 31311929 PMCID: PMC6635576 DOI: 10.1038/s41467-019-10974-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 06/10/2019] [Indexed: 11/08/2022] Open
Abstract
The concept of gauge field is a cornerstone of modern physics and the synthetic gauge field has emerged as a new way to manipulate particles in many disciplines. In optics, several schemes of Abelian synthetic gauge fields have been proposed. Here, we introduce a new platform for realizing synthetic SU(2) non-Abelian gauge fields acting on two-dimensional optical waves in a wide class of anisotropic materials and discover novel phenomena. We show that a virtual non-Abelian Lorentz force arising from material anisotropy can induce light beams to travel along Zitterbewegung trajectories even in homogeneous media. We further design an optical non-Abelian Aharonov-Bohm system which results in the exotic spin density interference effect. We can extract the Wilson loop of an arbitrary closed optical path from a series of gauge fixed points in the interference fringes. Our scheme offers a new route to study SU(2) gauge field related physics using optics.
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Affiliation(s)
- Yuntian Chen
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074, Wuhan, China
- Wuhan National Laboratory of Optoelectronics, Huazhong University of Science and Technology, 430074, Wuhan, China
| | - Ruo-Yang Zhang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
| | - Zhongfei Xiong
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074, Wuhan, China
| | - Zhi Hong Hang
- School of Physical Science and Technology and Institute for Advanced Study, Soochow University, 215006, Suzhou, China
| | - Jensen Li
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
| | - Jian Qi Shen
- Centre for Optical and Electromagnetic Research, State Key Laboratory of Modern Optical Instrumentations, Zhejiang University, 310058, Hangzhou, China.
| | - C T Chan
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.
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11
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Yuan L, Lin Q, Zhang A, Xiao M, Chen X, Fan S. Photonic Gauge Potential in One Cavity with Synthetic Frequency and Orbital Angular Momentum Dimensions. PHYSICAL REVIEW LETTERS 2019; 122:083903. [PMID: 30932579 DOI: 10.1103/physrevlett.122.083903] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Indexed: 05/22/2023]
Abstract
We explore a single degenerate optical cavity supporting a synthetic two-dimensional space, which includes the frequency and the orbital angular momentum (OAM) axes of light. We create the effective gauge potential inside this synthetic space and show that the system exhibits topologically protected one-way edge states along the OAM axis at the boundaries of the frequency dimension. In this synthetic space, we present a robust generation and manipulation of entanglement between the frequency and OAM of photons. Our Letter shows that a higher-dimensional synthetic space involving multiple degrees of freedom of light can be achieved in a "zero-dimensional" spatial structure, pointing towards a unique platform to explore topological photonics and to realize potential applications in optical communications and quantum information processing.
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Affiliation(s)
- Luqi Yuan
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qian Lin
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Anwei Zhang
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Meng Xiao
- Department of Electrical Engineering, and Ginzton Laboratory, Stanford University, Stanford, California 94305, USA
| | - Xianfeng Chen
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Shanhui Fan
- Department of Electrical Engineering, and Ginzton Laboratory, Stanford University, Stanford, California 94305, USA
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12
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Descheemaeker L, Ginis V, Viaene S, Tassin P. Optical Force Enhancement Using an Imaginary Vector Potential for Photons. PHYSICAL REVIEW LETTERS 2017; 119:137402. [PMID: 29341706 DOI: 10.1103/physrevlett.119.137402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Indexed: 06/07/2023]
Abstract
The enhancement of optical forces has enabled a variety of technological applications that rely on the optical control of small objects and devices. Unfortunately, optical forces are still too small for the convenient actuation of integrated switches and waveguide couplers. Here we show how the optical gradient force can be enhanced by an order of magnitude by making use of gauge materials inside two evanescently coupled waveguides. To this end, the gauge materials inside the cores should emulate imaginary vector potentials for photons pointing perpendicularly to the waveguide plane. Depending on the relative orientation of the vector potentials in neighboring waveguides, i.e., pointing away from or towards each other, the conventional attractive force due to an even mode profile may be enhanced, suppressed, or may even become repulsive. This and other new features indicate that the implementation of complex-valued vector potentials with non-Hermitian waveguide cores may further enhance our control over mode profiles and the associated optical forces.
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Affiliation(s)
- Lana Descheemaeker
- Applied Physics Research Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Vincent Ginis
- Applied Physics Research Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Sophie Viaene
- Applied Physics Research Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Department of Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
| | - Philippe Tassin
- Applied Physics Research Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Department of Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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13
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Xu Y, Fu Y, Chen H. Electromagnetic wave propagations in conjugate metamaterials. OPTICS EXPRESS 2017; 25:4952-4966. [PMID: 28380762 DOI: 10.1364/oe.25.004952] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this work, by employing field transformation optics, we deduce a special kind of materials called conjugate metamaterials, which can support intriguing electromagnetic wave propagations, such as negative refractions and lasing phenomena. These materials could also serve as substrates for making a subwavelength-resolution lens, and the so-called "perfect lens" is demonstrated to be a limiting case.
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14
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Alberucci A, Jisha CP, Marrucci L, Assanto G. Electromagnetic Confinement via Spin-Orbit Interaction in Anisotropic Dielectrics. ACS PHOTONICS 2016; 3:2249-2254. [PMID: 28217716 PMCID: PMC5312827 DOI: 10.1021/acsphotonics.6b00700] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Indexed: 06/06/2023]
Abstract
We investigate electromagnetic propagation in uniaxial dielectrics with a transversely varying orientation of the optic axis, the latter staying orthogonal everywhere in the propagation direction. In such a geometry, the field experiences no refractive index gradients, yet it acquires a transversely modulated Pancharatnam-Berry phase, that is, a geometric phase originating from a spin-orbit interaction. We show that the periodic evolution of the geometric phase versus propagation gives rise to a longitudinally invariant effective potential. In certain configurations, this geometric phase can provide transverse confinement and waveguiding. The theoretical findings are tested and validated against numerical simulations of the complete Maxwell's equations. Our results introduce and illustrate the role of geometric phases on electromagnetic propagation over distances well exceeding the diffraction length, paving the way to a whole new family of guided waves and waveguides that do not rely on refractive index tailoring.
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Affiliation(s)
- Alessandro Alberucci
- Optics
Laboratory, Tampere University of Technology, FI-33101 Tampere, Finland
- NooEL - Nonlinear Optics
and OptoElectronics Lab, University “Roma
Tre”, IT-00146 Rome, Italy
| | - Chandroth P. Jisha
- Centro
de Física do Porto, Faculdade de Ciências, Universidade do Porto, PT-4169-007 Porto, Portugal
| | - Lorenzo Marrucci
- Dipartimento
di Fisica, Università di Napoli Federico
II, IT-80100 Naples, Italy
- CNR-ISASI,
Institute of Applied Science and Intelligent Systems, IT-80078 Pozzuoli (NA), Italy
| | - Gaetano Assanto
- Optics
Laboratory, Tampere University of Technology, FI-33101 Tampere, Finland
- NooEL - Nonlinear Optics
and OptoElectronics Lab, University “Roma
Tre”, IT-00146 Rome, Italy
- CNR-ISC,
Institute for Complex Systems, IT-00185 Rome, Italy
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15
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Photonic crystals possessing multiple Weyl points and the experimental observation of robust surface states. Nat Commun 2016; 7:13038. [PMID: 27703140 PMCID: PMC5059475 DOI: 10.1038/ncomms13038] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 08/29/2016] [Indexed: 11/20/2022] Open
Abstract
Weyl points, as monopoles of Berry curvature in momentum space, have captured much attention recently in various branches of physics. Realizing topological materials that exhibit such nodal points is challenging and indeed, Weyl points have been found experimentally in transition metal arsenide and phosphide and gyroid photonic crystal whose structure is complex. If realizing even the simplest type of single Weyl nodes with a topological charge of 1 is difficult, then making a real crystal carrying higher topological charges may seem more challenging. Here we design, and fabricate using planar fabrication technology, a photonic crystal possessing single Weyl points (including type-II nodes) and multiple Weyl points with topological charges of 2 and 3. We characterize this photonic crystal and find nontrivial 2D bulk band gaps for a fixed kz and the associated surface modes. The robustness of these surface states against kz-preserving scattering is experimentally observed for the first time. To realize Weyl points carrying topological charges higher than one is challenging. Here, Chen et al. report a photonic crystal possessing single and multiple Weyl points with topological charges of two and three using planar fabrication technology.
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Yuan L, Shi Y, Fan S. Photonic gauge potential in a system with a synthetic frequency dimension. OPTICS LETTERS 2016; 41:741-4. [PMID: 26872177 DOI: 10.1364/ol.41.000741] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We generalize the concept of photonic gauge potential in real space by introducing an additional "synthetic" frequency dimension in addition to the real space dimensions. As an illustration, we consider a one-dimensional array of ring resonators, each supporting a set of resonant modes having a frequency comb with spacing Ω, and undergoing a refractive index modulation at the modulation frequency equal to Ω. We show that the modulation phase provides a gauge potential in the synthetic two-dimensional space with the dimensions being the frequency and the spatial axes. Such a gauge potential can create a topologically protected one-way edge state in the synthetic space that is useful for high-efficiency generation of higher-order side bands.
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A Wide-angle Multi-Octave Broadband Waveplate Based on Field Transformation Approach. Sci Rep 2015; 5:17532. [PMID: 26638829 PMCID: PMC4671019 DOI: 10.1038/srep17532] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 10/30/2015] [Indexed: 11/30/2022] Open
Abstract
Transformation optics (TO) offers a geometrical approach in designing optical components of any shapes. Although it has been proven to be a versatile and robust mathematical tool, TO has, however, limited control over electromagnetic (EM) field polarization in the process of coordinate transformation. Such a technique can be extended to a so-called “Field transformation (FT)” which provides direct control over the impedance and polarization signature of an arbitrary object. In this work, we demonstrate a FT application by designing and manufacturing a novel waveplate, which defies the fundamental limit of bandwidth and incident angles and has the ability of converting between TE (transverse electric) and TM (transverse magnetic) as well as LCP (left-handed circular polarization) and RCP (right-handed circular polarization). Such a waveplate can also be applied to different operating modes for both transmitted and reflected waves by adjusting its thickness and adding an optional metallic ground plane. The proposed design approach presents a remarkable degree of advance for designing future devices with arbitrary polarization controls, artificial waveguides or antenna substrates and polarization-enabled resonators with angle-insensitive functionalities. Our approach has far reaching implications applicable from radio to optical frequencies.
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