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Publications (10 of 605) Show all publications
Liu, Y., Sun, F. & He, S. (2018). Controlling lightwave in Riemann space by merging geometrical optics with transformation optics. Scientific Reports, 8(1), Article ID 514.
Open this publication in new window or tab >>Controlling lightwave in Riemann space by merging geometrical optics with transformation optics
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 514Article in journal (Refereed) Published
Abstract [en]

In geometrical optical design, we only need to choose a suitable combination of lenses, prims, and mirrors to design an optical path. It is a simple and classic method for engineers. However, people cannot design fantastical optical devices such as invisibility cloaks, optical wormholes, etc. by geometrical optics. Transformation optics has paved the way for these complicated designs. However, controlling the propagation of light by transformation optics is not a direct design process like geometrical optics. In this study, a novel mixed method for optical design is proposed which has both the simplicity of classic geometrical optics and the flexibility of transformation optics. This mixed method overcomes the limitations of classic optical design; at the same time, it gives intuitive guidance for optical design by transformation optics. Three novel optical devices with fantastic functions have been designed using this mixed method, including asymmetrical transmissions, bidirectional focusing, and bidirectional cloaking. These optical devices cannot be implemented by classic optics alone and are also too complicated to be designed by pure transformation optics. Numerical simulations based on both the ray tracing method and full-wave simulation method are carried out to verify the performance of these three optical devices.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-221681 (URN)10.1038/s41598-017-19015-0 (DOI)000419941400001 ()2-s2.0-85040445799 (Scopus ID)
Funder
Swedish Research Council, 2012AA030402
Note

QC 20180122

Available from: 2018-01-22 Created: 2018-01-22 Last updated: 2018-01-29Bibliographically approved
Gong, Y., Yang, B., Zhang, D., Hong, X., Lu, Y., He, S. & Chen, J. (2018). Crosstalk-aware multiple-AWG based optical interconnects for datacenter networks. Optics Communications, 426, 151-157
Open this publication in new window or tab >>Crosstalk-aware multiple-AWG based optical interconnects for datacenter networks
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2018 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 426, p. 151-157Article in journal (Refereed) Published
Abstract [en]

This paper proposes a crosstalk-aware passive optical interconnect architecture based on multiple arrayed waveguide gratings (AWGs). With two-stage cascaded AWGs, it can realize the communications not only within but also among the clusters for large-scale datacenters. To overcome serious crosstalk in multiple-AWG based optical interconnects, crosstalk suppression schemes are proposed. Proof-of-concept experiments are carried out to verify the necessity and feasibility of the proposed crosstalk suppression schemes for multiple-AWG based optical interconnects.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Crosstalk-aware interconnect, Data center network, Passive optical interconnect
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-229277 (URN)10.1016/j.optcom.2018.05.022 (DOI)2-s2.0-85047348276 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20180601

Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2018-06-01Bibliographically approved
Shi, K., Liao, R., Cao, G., Bao, F. & He, S. (2018). Enhancing thermal radiation by graphene-assisted hBN/SiO2 hybrid structures at the nanoscale. Optics Express, 26(10), A591-A601
Open this publication in new window or tab >>Enhancing thermal radiation by graphene-assisted hBN/SiO2 hybrid structures at the nanoscale
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2018 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 10, p. A591-A601Article in journal (Refereed) Published
Abstract [en]

A graphene-assisted hBN/SiO2, hybrid structure is proposed and demonstrated to enhance near-field thermal radiation (NFTR). Due to the complementarity between the hyperbolic phonon polaritons of hBN and the surface phonon polaritons of SiO2, at mid-infrared frequencies, coupling modes can remarkably improve the photon tunneling probability over a broad frequency band, especially when assisted by the surface plasmon polaritons of graphene sheets. Thus, the heat flux can exceed the blackbody limit by 4 orders of magnitude at a separation distance of 10 nm and reach 97% of the infinite limit of graphene-hBN multilayers using only two layers with a thickness of 20 nm each. The first graphene layer controls most of the heat flux, while the other layers can be used to regulate and optimize. The dynamic relationship between the chemical potential mu and the gap distance d are thoroughly discussed. Optimal heat flux of our graphene-assisted hBN/SiO2 hybrid structure with proper choices of (mu(1), mu(2), mu(3)) for different d (from 10 nm to 1000 nm) is further increased by 28.2% on average in comparison with the existing graphene-hBN triple-layer structure.

Place, publisher, year, edition, pages
OPTICAL SOC AMER, 2018
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-231224 (URN)10.1364/OE.26.00A591 (DOI)000432457600017 ()29801276 (PubMedID)2-s2.0-85047334238 (Scopus ID)
Note

QC 20180628

Available from: 2018-06-28 Created: 2018-06-28 Last updated: 2018-06-28Bibliographically approved
Hong, Y., Hong, X., He, S. & Chen, J. (2018). Hybrid Routing and Adaptive Spectrum Allocation for Flex-Grid Optical Interconnects. Journal of Optical Communications and Networking, 10(5), 506-514
Open this publication in new window or tab >>Hybrid Routing and Adaptive Spectrum Allocation for Flex-Grid Optical Interconnects
2018 (English)In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 10, no 5, p. 506-514Article in journal (Refereed) Published
Abstract [en]

A hybrid routing scheme with an adaptive spectrum assignment is proposed for flex-grid all-optical core switch supporting multihop transparent paths in data center networks. Compared with conventional spectrum assignment algorithms (RSA) developed for a multihop network with optical-electric-optical (OEO) conversion in every hop (i.e., RSA for EO) and that devised for an all-optical multihop network (i.e., RSA for AO), the present RSA algorithm provides better utilization of network resources. Being aware of the all-optical bypass path in hopping, the proposed RSA reduces the blocking probability due to lack of bandwidth-tunable transceivers, which is the major reason for blocking for an RSA for the EO. Similar to the RSA for the AO, the proposed RSA is compatible with the number-of-hops adaptive spectrum assignment, which improves spectrum efficiency. On the other hand, the new algorithm enhances connectivity by eliminating the number-of-hops limitation, which severely constrains the performance of RSA for the AO. Simulations for the system are carried out to investigate the performance of the new algorithm. The impacts of various parameters, such as traffic load, ratio of connection requests with different data rates, and resource configuration on the link cost, are studied in terms of network blocking probability (BP). The achievable traffic load of the proposed RSA under varied connection degrees (i.e., the maximum number of ports that one rack has in order to connect to the core switch) and number of racks is also assessed to keep BP no more than 0.1. The results show that the proposed RSA with appropriate cost functions outperforms the EO and AO, which implies that it has the highest scalability.

Place, publisher, year, edition, pages
Optical Society of America, 2018
Keywords
Data center network, Optical circuit switching, Optical interconnect, Routing and spectrum assignment (RSA)
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-229027 (URN)10.1364/JOCN.10.000506 (DOI)000432318600006 ()2-s2.0-85047218710 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20180531

Available from: 2018-05-31 Created: 2018-05-31 Last updated: 2018-05-31Bibliographically approved
Li, S., Sun, F., An, D. & He, S. (2018). Increasing Efficiency of a Wireless Energy Transfer System by Spatial Translational Transformation. IEEE transactions on power electronics, 33(4), 3325-3332
Open this publication in new window or tab >>Increasing Efficiency of a Wireless Energy Transfer System by Spatial Translational Transformation
2018 (English)In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 33, no 4, p. 3325-3332Article in journal (Refereed) Published
Abstract [en]

A magnetic translational projector (MTP) designed by transformation optics is applied to improve energy transfer efficiency in a wireless power transfer (WPT) system. Our numerical simulation results showtheMTP can greatly enhance energy transfer efficiency (e.g., nearly two orders, compared to the case without our MTP) in the WPT system, which is much larger than that of a previous method (i.e., using magnetic super-lens). A 3-D reduced MTPcomposed of layered isotropicmagnetic materials is designed, whose performance is verified by our 3-D numerical simulation in 10 MHz. The influence of loss in metamaterial on the performance of the proposed MTP is also studied, which shows that the MTP can still enhance energy transfer efficiency when loss exists. Further simulation is also carried out to show that the function of the MTP is not sensitive to large perturbation. Finally, detailed experimental suggestion for implementing the simplified MTP, which is composed of layered medium is given and then verified by our numerical simulation.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018
Keywords
Magnetic device, metamaterial, transformation optics, wireless energy transfer
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-222165 (URN)10.1109/TPEL.2017.2703591 (DOI)000422933400050 ()2-s2.0-85040778782 (Scopus ID)
Note

QC 20180205

Available from: 2018-02-05 Created: 2018-02-05 Last updated: 2018-02-05Bibliographically approved
Sun, F. & He, S. (2018). Invisible gateway for both light waves and rays. Optics Express, 26(1), 165-172
Open this publication in new window or tab >>Invisible gateway for both light waves and rays
2018 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 1, p. 165-172Article in journal (Refereed) Published
Abstract [en]

Considering that previous invisible gateways (an open entrance that only blocks electromagnetic waves) based on super-scatters designed by transformation optics cannot effectively work for narrow beams and light rays that do not touch negative refractive index material, we explore a new way to realize an improved invisible gateway that can give a good performance for both light waves and rays. In all previous invisible gateways, they require a finite thickness of the wall and the gateway. For the improved invisible gateway proposed in this study, there is no requirement on the thickness of the wall and gateway, i.e. the wall and gateway can be infinitely thin. Our study will go a further step to realize the invisible gateway in fiction.

Place, publisher, year, edition, pages
OPTICAL SOC AMER, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-221942 (URN)10.1364/OE.26.000165 (DOI)000419549600014 ()29328288 (PubMedID)2-s2.0-85040189274 (Scopus ID)
Note

QC 20180130

Available from: 2018-01-30 Created: 2018-01-30 Last updated: 2018-01-30Bibliographically approved
Li, B., Sun, F. & He, S. (2018). Reducing the dimensions of acoustic devices using anti-acoustic-null media. APPLIED PHYSICS EXPRESS, 11(2), Article ID 024301.
Open this publication in new window or tab >>Reducing the dimensions of acoustic devices using anti-acoustic-null media
2018 (English)In: APPLIED PHYSICS EXPRESS, ISSN 1882-0778, Vol. 11, no 2, article id 024301Article in journal (Refereed) Published
Abstract [en]

An anti-acoustic-null medium (anti-ANM), a special homogeneous medium with anisotropic mass density, is designed by transformation acoustics (TA). Anti-ANM can greatly compress acoustic space along the direction of its main axis, where the size compression ratio is extremely large. This special feature can be utilized to reduce the geometric dimensions of classic acoustic devices. For example, the height of a parabolic acoustic reflector can be greatly reduced. We also design a brass-air structure on the basis of the effective medium theory to materialize the anti-ANM in a broadband frequency range. Numerical simulations verify the performance of the proposed anti-ANM.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2018
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-222402 (URN)10.7567/APEX.11.024301 (DOI)000423332300001 ()2-s2.0-85042636923 (Scopus ID)
Note

QC 20180223

Available from: 2018-02-23 Created: 2018-02-23 Last updated: 2018-05-24Bibliographically approved
He, W., Xu, B., Gustafsson, M., Ying, Z. & He, S. (2018). RF Compliance Study of Temperature Elevation in Human Head Model Around 28 GHz for 5G User Equipment Application: Simulation Analysis. IEEE Access, 6
Open this publication in new window or tab >>RF Compliance Study of Temperature Elevation in Human Head Model Around 28 GHz for 5G User Equipment Application: Simulation Analysis
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2018 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 6Article in journal (Refereed) Published
Abstract [en]

The crowdedness of current cellular bands and the demand for higher transmission speed prompt the use of the millimeter-wave spectrum for the next-generation mobile communication. In the millimeter-wave frequencies, the dosimetric quantity for human exposure to electromagnetic fields changes from the specific absorption rate to incident power density. In this paper, we used 28-GHz beam-steering patch arrays, a dipole antenna, and plane waves to investigate the temperature elevation in a multi-layer model of human head and its correlation with power density metrics. The power density averaged over one square-centimeter in free space and the peak temperature elevation in tissue at 28 GHz have good correlation. The peak temperature elevation indicated by the power density averaged one square-centimeter also agrees well with the peak temperature elevation induced by the plane waves. The results show that the averaging area of a few square-centimeters may be a good candidate for the spatial-average power density. The findings provide valuable input to the ongoing revision and updating of relevant safety standards and guidelines.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018
Keywords
28 GHz, 5G, antenna array, human head, incident power density, millimeter wave, RF compliance, safety guidelines, safety standards, temperature elevation, user equipment
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-224049 (URN)10.1109/ACCESS.2017.2776145 (DOI)000425675300025 ()2-s2.0-85035807157 (Scopus ID)
Note

QC 20180316

Available from: 2018-03-16 Created: 2018-03-16 Last updated: 2018-03-16Bibliographically approved
Shi, K., Bao, F. & He, S. (2018). Spectral Control of Near-Field Thermal Radiation With Periodic Cross Resonance Metasurfaces. IEEE Journal of Quantum Electronics, 54(1), Article ID 7000107.
Open this publication in new window or tab >>Spectral Control of Near-Field Thermal Radiation With Periodic Cross Resonance Metasurfaces
2018 (English)In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 54, no 1, article id 7000107Article in journal (Refereed) Published
Abstract [en]

Near-field thermal spectra can be engineered using periodic cross resonance metasurfaces. Structures consisting of single crosses, double crosses, and multiple crosses are proposed to control the spectral heat flux from narrow band to broadband with the Fabry-Perot-cavity-like effect and the interaction between the emitter and receiver. Radiation peaks originating from the cross structures split into two adjacent peaks in the near-field, due to the separate contributions of s- and p-polariton modes. Their frequency can be manipulated by adjusting the length of the crosses. Multiple radiation peaks can be generated by double crosses, and due to the strong coupling of resonance modes, multiple crosses can yield a broadband thermal spectrum ranging from 100-180 THz, with the total heat flux two orders of magnitude above the blackbody limit. The inherent physical mechanisms are illustrated by analyzing the energy transmission coefficients of the cross structures. The features of the radiation peaks and spectra are robust to the change of the gap distance or the temperature, which is advantageous for both the experimental design and fabrication of thermal radiation devices.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Keywords
Near-field, thermal radiation spectrum, optical resonance, periodic structures
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-222412 (URN)10.1109/JQE.2018.2791639 (DOI)000423191500001 ()2-s2.0-85041112109 (Scopus ID)
Note

QC 20180228

Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2018-05-24Bibliographically approved
Jiang, W., Ma, Y. & He, S. (2018). Static Magnetic Cloak without a Superconductor. Phronimon, 9(5), Article ID 054041.
Open this publication in new window or tab >>Static Magnetic Cloak without a Superconductor
2018 (English)In: Phronimon, ISSN 1561-4018, E-ISSN 2331-7019, Vol. 9, no 5, article id 054041Article in journal (Refereed) Published
Abstract [en]

Similar to its electromagnetic counterpart, magnetic cloaking also has very important technological applications. However, the traditional method to build a static magnetic cloak requires the use of superconducting materials as the diamagnetic component, which seriously limits the practical potential because of the cryogenic condition. We show that a diamagnetic active current boundary combined with a high-permeability magnetic inner shell (MIS) can be designed to solve this problem, rendering an ideal magnetic cloaking effect at zero frequency. We first theoretically prove that a current boundary could magnetically behave as a superconductor to external observers. Based on this phenomena, we introduce a high-permeability MIS made of magnetically ultrasoft metallic sheets (permeability mu > 10(3)) and experimentally prove that the bilayer combination can exactly balance out the disturbance to the external probing field and, meanwhile, have a large invisible inner space. We also show that the active boundary currents can be accordingly configured to overcome the permeability and frequency band limits, leading to a robust cloak over the entire quasistatic frequency region. Our work creates an efficient way to circumvent the traditional limits of metamaterials to build magnetic cloaks for ultralow frequencies. The active-passive hybrid approach could be generally extended to yield other artificial magnetic devices or systems as well.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-230496 (URN)10.1103/PhysRevApplied.9.054041 (DOI)000433294000001 ()
Note

QC 20180615

Available from: 2018-06-15 Created: 2018-06-15 Last updated: 2018-06-15Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-3401-1125

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