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Thermal photonics with broken symmetries

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eLight 2022年第1期2卷 317-336页

作者： Tianji Liu Cheng Guo Wei Li shanhui fan GPL Photonics Laboratory State Key Laboratory of Applied OpticsFine Mechanics and PhysicsChangchun Institute of OpticsChinese Academy of SciencesChangchun 130033China Department of Applied Physics Stanford UniversityStanfordCA 94305USA Department of Electrical Engineering Ginzton LaboratoryStanford UniversityStanfordCA 94305USA

Nanophotonic engineering provides an effective platform to manipulate thermal emission on-demand,enabling unprecedented heat management superior to conventional bulk materials.Amongst a plethora of nanophotonic structures,symmetries play an important role in controlling radiative heat transfer in both near-field and far-field.In physics,broken symmetries generally increase the degree of freedom in a system,enriching the understanding of physical mechanisms and bringing many exciting opportunities for novel applications.In this review,we discussed the underlying physics and functionalities of nanophotonic structures with broken geometrical symmetries,engineered mode symmetries,and broken reciprocity for the control of thermal emission.We overview a variety of physical phenomena and interesting applications,and provide the outlook for future development.

关键词： materials field symmetries

Thermodynamic limits for simultaneous energy harvesting from the hot sun and cold outer space

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Light(Science & Applications) 2020年第1期9卷 1373-1383页

作者： Wei Li Siddharth Buddhiraju shanhui fan Department of Electrical Engineering Ginzton LaboratoryStanford UniversityStanfordCA 94305USA

The sun and outer space are two of the most important fundamental thermodynamic resources for renewable energy harvesting.A significant amount of work has focused on understanding the fundamental limit of energy harvesting from the sun.More recently,there have been several theoretical analyses of the fundamental limit of energy harvesting from outer space.However,far less is understood about the fundamental limits of simultaneous energy harvesting from both the sun and outer space.Here,we consider and introduce various schemes that are capable of simultaneous energy harvesting and elucidate the fundamental thermodynamic limits of these schemes.We show that the theoretical limits can far exceed the previously established limit associated with utilizing only one thermodynamic resource.Our results highlight the significant potential of simultaneous energy harvesting and indicate new fundamental opportunities for improving the efficiency of energy harvesting systems.

关键词： outer harvesting simultaneous

Multi-dimensional band structure spectroscopy in the synthetic frequency dimension

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Light(Science & Applications) 2023年第7期12卷 1425-1433页

作者： Dali Cheng Eran Lustig Kai Wang shanhui fan Ginzton Laboratory and Department of Electrical Engineering Stanford UniversityStanfordCA94305USA Department of Physics McGll UniversityMontrealQC H3A 2T8Canada

The concept of synthetic dimensions in photonics provides a versatile platform in exploring multi-dimensional physics.Many of these physics are characterized by band structures in more than one dimensions.Existing efforts on band structure measurements in the photonic synthetic frequency dimension however are limited to either onedimensional Brillouin zones or one-dimensional subsets of multi-dimensional Billouin zones.Here we theoretically propose and experimentally demonstrate a method to fully measure multi-dimensional band structures in the synthetic frequency dimension.We use a single photonic resonator under dynamical modulation to create a multidimensional synthetic frequency lattice.We show that the band structure of such a lattice over the entire multidimensional Brillouin zone can be measured by introducing a gauge potential into the lattice Hamiltonian.Using this method,we perform experimental measurements of two-dimensional band structures of a Hermitian and a non-Hermitian Hamiltonian.The measurements reveal some of the general properties of point-gap topology of the non-Hermitian Hamiltonian in more than one dimensions.Our results demonstrate experimental capabilities to fully characterize high-dimensional physical phenomena in the photonic synthetic frequency dimension.

关键词： resonator synthetic dimensional

Higher-order topological insulators in synthetic dimensions

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Light(Science & Applications) 2020年第1期9卷 831-839页

作者： Avik Dutt Momchil Minkov Ian A.D.Williamson shanhui fan Ginzton Laboratory and Department of Electrical Engineering Stanford UniversityStanfordCA 94305USA

Conventional topological insulators support boundary states with dimension one lower than that of the bulk system that hosts them,and these states are topologically protected due to quantized bulk dipole moments.Recently,higherorder topological insulators have been proposed as a way of realizing topological states with dimensions two or more lower than that of the bulk due to the quantization of bulk quadrupole or octupole moments.However,all these proposals as well as experimental realizations have been restricted to real-space dimensions.Here,we construct photonic higher-order topological insulators(PHOTIs)in synthetic dimensions.We show the emergence of a quadrupole PHOTI supporting topologically protected corner modes in an array of modulated photonic molecules with a synthetic frequency dimension,where each photonic molecule comprises two coupled rings.By changing the phase difference of the modulation between adjacent coupled photonic molecules,we predict a dynamical topological phase transition in the PHOTI.Furthermore,we show that the concept of synthetic dimensions can be exploited to realize even higher-order multipole moments such as a fourth-order hexadecapole(16-pole)insulator supporting 0D corner modes in a 4D hypercubic synthetic lattice that cannot be realized in real-space lattices.

关键词： topological dimensions insulator

Metamaterials for radiative sky cooling

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National Science Review 2018年第2期5卷 132-133页

作者： shanhui fan Aaswath Raman Ginzton Laboratory Department of Electrical Engineering Stanford University Department of Electrical and Systems Engineering University of Pennsylvania

From fundamental thermodynamic considerations,in order to convert heat to usable work,it is important to have a heat source with a temperature that is as high as possible,and to have a heat sink with a temperature that is as low as possible.The vast majority of energy conversion processes at the moment use our ambient surroundings on Earth itself,with a

关键词： METAMATERIALS THERMODYNAMICS

Dissipation in few-photon waveguide transport[Invited]

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Photonics Research 2013年第3期1卷 110-114页

作者： Eden Rephaeli shanhui fan Department of Applied Physics Stanford UniversityStanfordCalifornia 94305USA Department of Electrical Engineering Stanford UniversityStanfordCalifornia 94305USA

We develop a formulation of few-photon Fock-space waveguide transport that includes dissipation in the form of reservoir coupling.We develop the formalism for the case of a two-level atom and then show that our formalism leads to a simple rule that allows one to obtain the dissipative description of a system from the nondissipative case.

关键词： waveguide coupling. transport

Angle-selective perfect absorption with two-dimensional materials

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Light(Science & Applications) 2015年第1期4卷 59-64页

作者： Linxiao Zhu Fengyuan Liu Hongtao Lin Juejun Hu Zongfu Yu Xinran Wang shanhui fan Department of Applied Physics Stanford UniversityStanfordCA 94305USA National Laboratory of Solid State Microstructures School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China Department of Materials Science and Engineering Massachusetts Institute of TechnologyMA 02139USA Department of Electrical and Computer Engineering University of Wisconsin-MadisonMadisonWI 53706USA Department of Electrical Engineering Ginzton LaboratoryStanford UniversityStanfordCA 94305USA

Two-dimensional(2D)materials have great potential in photonic and optoelectronic devices.However,the relatively weak light absorption in 2D materials hinders their application in practical devices.Here,we propose a general approach to achieve angleselective perfect light absorption in 2D materials.As a demonstration of the concept,we experimentally show giant light absorption by placing large-area single-layer graphene on a structure consisting of a chalcogenide layer atop a mirror and achieving a total absorption of 77.6%in the mid-infrared wavelength range(~13μm),where the graphene contributes a record-high 47.2%absorptivity of mid-infrared light.Construction of such an angle-selective thin optical element is important for solar and thermal energy harvesting,photo-detection and sensing applications.Our study points to a new opportunity to combine 2D materials with photonic structures to enable novel device applications.

关键词： angle-selective perfect absorption angle-selective thin optical element graphene mid-infrared two-dimensional materials

Low-overhead distribution strategy for simulation and optimization of large-area metasurfaces

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npj Computational Materials 2022年第1期8卷 735-740页

作者： Jinhie Skarda Rahul Trivedi Logan Su Diego Ahmad-Stein Hyounghan Kwon Seunghoon Han shanhui fan Jelena Vučković E.L.Ginzton Laboratory Stanford UniversityStanfordCA 94305USA Max-Planck-Institut fur Quantenoptik Hans-Kopfermann-Str.185748 GarchingGermany Department of electrical and computer engineering University of WashingtonSeattle 98195USA Samsung Advanced Institute of Technology Samsung ElectronicsSuwon-siGyeonggi-do 443-803Republic of Korea

Fast and accurate electromagnetic simulation of large-area metasurfaces remains a major obstacle in automating their design.In this paper,we propose a metasurface simulation distribution strategy which achieves a linear reduction in the simulation time with the number of compute nodes.Combining this distribution strategy with a GPU-based implementation of the Transition-matrix method,we perform accurate simulations and adjoint sensitivity analysis of large-area metasurfaces.We demonstrate ability to perform a distributed simulation of large-area metasurfaces(over 600λ×600λ),while accurately accounting for scatterer-scatterer interactions significantly beyond the locally periodic approximation.

关键词： distribution surfaces scatter

Structured 3D linear space–time light bullets by nonlocal nanophotonics

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Light(Science & Applications) 2021年第9期10卷 1687-1701页

作者： Cheng Guo Meng Xiao Meir Orenstein shanhui fan Department of Applied Physics Stanford UniversityStanfordCA94305USA Key Laboratory of Artificial Micro-and Nano-structures of Ministry of Education and School of Physics and Technology Wuhan UniversityWuhan430072China Andrew&Erna Viterbi Department of Electrical Engineering Technion–Israel Institute of TechnologyHaifa32000Israel Ginzton Laboratory and Department of Electrical Engineering Stanford UniversityStanfordCA94305USA

We propose the generation of 3D linear light bullets propagating in free space using a single passive nonlocal optical surface.The nonlocal nanophotonics can generate space–time coupling without any need for bulky pulse-shaping and spatial modulation techniques.Our approach provides simultaneous control of various properties of the light bullets,including the external properties such as the group velocity and the propagation distance,and internal degrees of freedom such as the spin angular momentum and the orbital angular momentum.

关键词： surface angular nonlocal