The unidirectional excitation of near-field optical modes is a fundamental prerequisite for many photonic applications,such as wireless power transfer and information communications.We experimentally construct all-ele...The unidirectional excitation of near-field optical modes is a fundamental prerequisite for many photonic applications,such as wireless power transfer and information communications.We experimentally construct all-electric Huygens and spin metasources and demonstrate anomalous unidirectional excitation of high-k hyperbolic modes in two types of hyperbolic metasurfaces.We use a Huygens metasource to study the unidirectional excitation of hyperbolic bulk modes in a planar hyperbolic metamaterial(HMM).Specifically,unidirectional excitation is the same as that in free space in the vertical direction,but opposite to that in free space in the horizontal direction.This anomalous unidirectional excitation is determined by the anisotropic HMM dispersion.In addition,we use a spin metasource to observe the anomalous photonic spin Hall effect in a planar hyperbolic waveguide.For a near-field source with a specific spin,the guide mode with a fixed directional wave vector is excited due to spin-momentum locking.Because the directions of momentum and energy flows in the HMM waveguide are opposite,the unidirectional excitation of hyperbolic guided modes is reversed.Our results not only uncover the sophisticated electromagnetic functionalities of metasources in the near-field but may also provide novel opportunities for the development of integrated optical devices.展开更多
Despite the success of guided wave ultrasonic inspection for internal defect detection in steel pipes,its application on polyethylene(PE)pipe remains relatively unexplored.The growth of internal cracks in PE pipe seve...Despite the success of guided wave ultrasonic inspection for internal defect detection in steel pipes,its application on polyethylene(PE)pipe remains relatively unexplored.The growth of internal cracks in PE pipe severely affects its pressure-holding capacity,hence the early detection of internal cracks is crucial for effective pipeline maintenance strategies.This study extends the scope of guided wave-based ultrasonic testing to detect the growth of internal cracks in a natural gas distribution PE pipe.Laboratory experiments and a finite element model were planned to study the wave-crack interaction at different stages of axially oriented internal crack growth with a piezoceramic transducer-based setup arranged in a pitch-catch configuration.Mode dispersion analysis supplemented with preliminary experiments was performed to isolate the optimal inspection frequency,leading to the selection of the T(0,1)mode at 50-kHz for the investigation.A transmission index based on the energy of the T(0,1)mode was developed to trace the extent of simulated crack growth.The findings revealed an inverse linear correlation between the transmission index and the crack depth for crack growth beyond 20%crack depth.展开更多
Dielectric optical antennas have emerged as a promising nanophotonic architecture for manipulating the propagation and localization of light.However,the optically induced Mie resonances in an isolated nanoantenna are ...Dielectric optical antennas have emerged as a promising nanophotonic architecture for manipulating the propagation and localization of light.However,the optically induced Mie resonances in an isolated nanoantenna are normally with broad spectra and poor𝑄-factors,limiting their performances in sensing,lasing,and nonlinear optics.Here,we dramatically enhance the𝑄-factors of Mie resonances in silicon(Si)nanoparticles across the optical band by arranging the nanoparticles in a periodic lattice.We select monocrystalline Si with negligible material losses and develop a unique method to fabricate nanoparticle arrays on a quartz substrate.By extinction dispersion measurements and electromagnetic analysis,we can identify three types of collective Mie resonances with𝑄-factors∼500 in the same nanocylinder arrays,including surface lattice resonances,bound states in the continuum,and quasi-guided modes.Our work paves the way for fundamental research in strong light-matter interactions and the design of highly efficient light-emitting metasurfaces.展开更多
We have fabricated a series of square-lattice hole photonic crystal (2PhC) arrays simultaneously at the un-current injection region on a special sample of GaN based light emitting diode (LED) by using focus ion beam m...We have fabricated a series of square-lattice hole photonic crystal (2PhC) arrays simultaneously at the un-current injection region on a special sample of GaN based light emitting diode (LED) by using focus ion beam milling (FIBM). The lattice constants of the 2PhC arrays vary from 230 to 1500 nm,while the 2PhC arrays have a constant area of about 9 μm×18 μm and a fixed depth of 150±10 nm which approaches but does not penetrate the active layer. Microscopic electroluminescence images and spectral measurements consistently confirm that the top emitting intensities from different 2PhCs are all enhanced compared with the unpatterned region. It is demonstrated that the output coupling of propagating guided modes is realized by the diffracted transmission of the 2PhCs. The enhancement factors of the guided modes compared with the unpatterned region are plotted as function of the lattice constant. It is found that the highest enhancements for the extraction of guided modes were obtained for the lattice constant of 230 and 460 nm of 2PhCs. The results are discussed by the two-dimensional rigorous coupled wave analysis (RCWA).展开更多
We design and demonstrate a type of multiplexed hologram by nanoscatterers inside a dielectric-loaded plasmonic waveguide with guided-wave illuminations. The mode division multiplexed hologram（MDMH） is fulfilled by ...We design and demonstrate a type of multiplexed hologram by nanoscatterers inside a dielectric-loaded plasmonic waveguide with guided-wave illuminations. The mode division multiplexed hologram（MDMH） is fulfilled by the scattering of guided waves to free space with respect to different modes. According to different mode numbers, these guided modes have different responses to the multiplexed hologram, and then give rise to different holographic images in reconstructions. In experiments, we show two kinds of MDMHs based on TM0∕TE0 and TE0∕TE1 modes as examples. Our approach could enrich the holography method that favors on-chip integration.展开更多
A modified alternating direction implicit approach is proposed to discretize the three-dimensional full-vectorial beam propagation method （3D-FV-BPM） formulation along the longitudinal direction. The cross-coupling ...A modified alternating direction implicit approach is proposed to discretize the three-dimensional full-vectorial beam propagation method （3D-FV-BPM） formulation along the longitudinal direction. The cross-coupling terms （CCTs） are neglected at the first substep, and then double used at the second substep. The order of two substeps is reversed for each transverse electric field component so that the CCTs are always expressed in an implicit form, thus the calculation is efficient and stable. Based on the multinomial interpolation, a universal finite difference scheme with a high accuracy is developed to approximate the 3D-FV-BPM formulation along the transverse directions, in which the discontinuities of the normal components of the electric field across the abrupt dielectric interfaces are taken into account and can be applied to both uniform and non-uniform grids. The corresponding imaginary-distance procedure is first applied to a buried rectangular and a GaAs-based deeply-etched rib waveguide. The field patterns and the normalized propagation constants of the fundamental and the first order modes are presented and the hybrid nature of the full-vectorial guided-modes is demonstrated, which shows the validity and utility of the present approach. Then the modal characteristics of the deeply- and shallow-etched rib waveguides based on the InGaAsp/InGaAsP strained multiple quantum wells in InP substrate are investigated in detail. The results are necessary for modeling and the design of the planar lightwave circuits or photonic integrated circuits based on these waveguides.展开更多
Guided modes in a hollow optical fiber are investigated using both scalar approximation and exact vectorial analysis. Effective indices of modes are seen to exhibit "nearly degenerate" groups. Besides provid...Guided modes in a hollow optical fiber are investigated using both scalar approximation and exact vectorial analysis. Effective indices of modes are seen to exhibit "nearly degenerate" groups. Besides providing an insight of modal characteristics, the analysis would prove to be useful to define design parameters for realizing components based on these fibers, and to explore new possibilities.展开更多
Extreme Mei-yu rainfall(MYR)can cause catastrophic impacts to the economic development and societal welfare in China.While significant improvements have been made in climate models,they often struggle to simulate loca...Extreme Mei-yu rainfall(MYR)can cause catastrophic impacts to the economic development and societal welfare in China.While significant improvements have been made in climate models,they often struggle to simulate local-to-regional extreme rainfall(e.g.,MYR).Yet,large-scale climate modes(LSCMs)are relatively well represented in climate models.Since there exists a close relationship between MYR and various LSCMs,it might be possible to develop causality-guided statistical models for MYR prediction based on LSCMs.These statistical models could then be applied to climate model simulations to improve the representation of MYR in climate models.In this pilot study,it is demonstrated that skillful causality-guided statistical models for MYR can be constructed based on known LSCMs.The relevancy of the selected predictors for statistical models are found to be consistent with the literature.The importance of temporal resolution in constructing statistical models for MYR is also shown and is in good agreement with the literature.The results demonstrate the reliability of the causality-guided approach in studying complex circulation systems such as the East Asian summer monsoon(EASM).Some limitations and possible improvements of the current approach are discussed.The application of the causality-guided approach opens up a new possibility to uncover the complex interactions in the EASM in future studies.展开更多
基金This work was supported by the National Key R&D Program of China(Grant No.2016YFA0301101)the National Natural Science Foundation of China(NSFC)(Grant Nos.12004284,11775159,61621001,and 11935010)+3 种基金the Natural Science Foundation of Shanghai(Grant Nos.18ZR1442800 and 18JC1410900)China Postdoctoral Science Foundation(Grant Nos.2019TQ0232 and 2019M661605)the Shanghai Super Postdoctoral Incentive Programand the Opening Project of Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology.The authors declare no conflicts of interest.
文摘The unidirectional excitation of near-field optical modes is a fundamental prerequisite for many photonic applications,such as wireless power transfer and information communications.We experimentally construct all-electric Huygens and spin metasources and demonstrate anomalous unidirectional excitation of high-k hyperbolic modes in two types of hyperbolic metasurfaces.We use a Huygens metasource to study the unidirectional excitation of hyperbolic bulk modes in a planar hyperbolic metamaterial(HMM).Specifically,unidirectional excitation is the same as that in free space in the vertical direction,but opposite to that in free space in the horizontal direction.This anomalous unidirectional excitation is determined by the anisotropic HMM dispersion.In addition,we use a spin metasource to observe the anomalous photonic spin Hall effect in a planar hyperbolic waveguide.For a near-field source with a specific spin,the guide mode with a fixed directional wave vector is excited due to spin-momentum locking.Because the directions of momentum and energy flows in the HMM waveguide are opposite,the unidirectional excitation of hyperbolic guided modes is reversed.Our results not only uncover the sophisticated electromagnetic functionalities of metasources in the near-field but may also provide novel opportunities for the development of integrated optical devices.
基金the financial support provided by USDOT Pipeline and Hazardous Materials Safety Administration (PHMSA)through the Competitive Academic Agreement Program (CAAP)。
文摘Despite the success of guided wave ultrasonic inspection for internal defect detection in steel pipes,its application on polyethylene(PE)pipe remains relatively unexplored.The growth of internal cracks in PE pipe severely affects its pressure-holding capacity,hence the early detection of internal cracks is crucial for effective pipeline maintenance strategies.This study extends the scope of guided wave-based ultrasonic testing to detect the growth of internal cracks in a natural gas distribution PE pipe.Laboratory experiments and a finite element model were planned to study the wave-crack interaction at different stages of axially oriented internal crack growth with a piezoceramic transducer-based setup arranged in a pitch-catch configuration.Mode dispersion analysis supplemented with preliminary experiments was performed to isolate the optimal inspection frequency,leading to the selection of the T(0,1)mode at 50-kHz for the investigation.A transmission index based on the energy of the T(0,1)mode was developed to trace the extent of simulated crack growth.The findings revealed an inverse linear correlation between the transmission index and the crack depth for crack growth beyond 20%crack depth.
基金the National Natural Science Foundation of China(62120106001,62275184,61875143,and 62104165)the Natural Science Foundation of Jiangsu Province(BK20200859,BK20200857,and BK20210713)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions.JGR and PB also acknowledge financial support from Nederlandse Organisatie voor Wetenschappelijk Onderzoek(NWO)(Vici 680-47-628).
文摘Dielectric optical antennas have emerged as a promising nanophotonic architecture for manipulating the propagation and localization of light.However,the optically induced Mie resonances in an isolated nanoantenna are normally with broad spectra and poor𝑄-factors,limiting their performances in sensing,lasing,and nonlinear optics.Here,we dramatically enhance the𝑄-factors of Mie resonances in silicon(Si)nanoparticles across the optical band by arranging the nanoparticles in a periodic lattice.We select monocrystalline Si with negligible material losses and develop a unique method to fabricate nanoparticle arrays on a quartz substrate.By extinction dispersion measurements and electromagnetic analysis,we can identify three types of collective Mie resonances with𝑄-factors∼500 in the same nanocylinder arrays,including surface lattice resonances,bound states in the continuum,and quasi-guided modes.Our work paves the way for fundamental research in strong light-matter interactions and the design of highly efficient light-emitting metasurfaces.
基金supported by the National Basic Research Program of China ("973" Project) (Grant Nos.2007CB307004,2006CB921607)the National Natural Science Foundation of China (Grant Nos.60776041,60976009,U0834001)
文摘We have fabricated a series of square-lattice hole photonic crystal (2PhC) arrays simultaneously at the un-current injection region on a special sample of GaN based light emitting diode (LED) by using focus ion beam milling (FIBM). The lattice constants of the 2PhC arrays vary from 230 to 1500 nm,while the 2PhC arrays have a constant area of about 9 μm×18 μm and a fixed depth of 150±10 nm which approaches but does not penetrate the active layer. Microscopic electroluminescence images and spectral measurements consistently confirm that the top emitting intensities from different 2PhCs are all enhanced compared with the unpatterned region. It is demonstrated that the output coupling of propagating guided modes is realized by the diffracted transmission of the 2PhCs. The enhancement factors of the guided modes compared with the unpatterned region are plotted as function of the lattice constant. It is found that the highest enhancements for the extraction of guided modes were obtained for the lattice constant of 230 and 460 nm of 2PhCs. The results are discussed by the two-dimensional rigorous coupled wave analysis (RCWA).
基金supported by the National Key R&D Program of China(Nos.2017YFA0303700 and 2016YFA0202103)the National Natural Science Foundation of China(Nos.11674167 and 11621091)the support of PAPD from Jiangsu Province and the Dengfeng Project B of Nanjing University
文摘We design and demonstrate a type of multiplexed hologram by nanoscatterers inside a dielectric-loaded plasmonic waveguide with guided-wave illuminations. The mode division multiplexed hologram（MDMH） is fulfilled by the scattering of guided waves to free space with respect to different modes. According to different mode numbers, these guided modes have different responses to the multiplexed hologram, and then give rise to different holographic images in reconstructions. In experiments, we show two kinds of MDMHs based on TM0∕TE0 and TE0∕TE1 modes as examples. Our approach could enrich the holography method that favors on-chip integration.
文摘A modified alternating direction implicit approach is proposed to discretize the three-dimensional full-vectorial beam propagation method （3D-FV-BPM） formulation along the longitudinal direction. The cross-coupling terms （CCTs） are neglected at the first substep, and then double used at the second substep. The order of two substeps is reversed for each transverse electric field component so that the CCTs are always expressed in an implicit form, thus the calculation is efficient and stable. Based on the multinomial interpolation, a universal finite difference scheme with a high accuracy is developed to approximate the 3D-FV-BPM formulation along the transverse directions, in which the discontinuities of the normal components of the electric field across the abrupt dielectric interfaces are taken into account and can be applied to both uniform and non-uniform grids. The corresponding imaginary-distance procedure is first applied to a buried rectangular and a GaAs-based deeply-etched rib waveguide. The field patterns and the normalized propagation constants of the fundamental and the first order modes are presented and the hybrid nature of the full-vectorial guided-modes is demonstrated, which shows the validity and utility of the present approach. Then the modal characteristics of the deeply- and shallow-etched rib waveguides based on the InGaAsp/InGaAsP strained multiple quantum wells in InP substrate are investigated in detail. The results are necessary for modeling and the design of the planar lightwave circuits or photonic integrated circuits based on these waveguides.
文摘Guided modes in a hollow optical fiber are investigated using both scalar approximation and exact vectorial analysis. Effective indices of modes are seen to exhibit "nearly degenerate" groups. Besides providing an insight of modal characteristics, the analysis would prove to be useful to define design parameters for realizing components based on these fibers, and to explore new possibilities.
基金supported by the UK-China Research and Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP)China as part of the Newton Fund。
文摘Extreme Mei-yu rainfall(MYR)can cause catastrophic impacts to the economic development and societal welfare in China.While significant improvements have been made in climate models,they often struggle to simulate local-to-regional extreme rainfall(e.g.,MYR).Yet,large-scale climate modes(LSCMs)are relatively well represented in climate models.Since there exists a close relationship between MYR and various LSCMs,it might be possible to develop causality-guided statistical models for MYR prediction based on LSCMs.These statistical models could then be applied to climate model simulations to improve the representation of MYR in climate models.In this pilot study,it is demonstrated that skillful causality-guided statistical models for MYR can be constructed based on known LSCMs.The relevancy of the selected predictors for statistical models are found to be consistent with the literature.The importance of temporal resolution in constructing statistical models for MYR is also shown and is in good agreement with the literature.The results demonstrate the reliability of the causality-guided approach in studying complex circulation systems such as the East Asian summer monsoon(EASM).Some limitations and possible improvements of the current approach are discussed.The application of the causality-guided approach opens up a new possibility to uncover the complex interactions in the EASM in future studies.
