In Asia,about 1%-19.1% of the population suffer fromurolithiasis.However,due to variations in socio-economic status and geographic locations,the prevalence and incidence have changed in different countries or regions ...In Asia,about 1%-19.1% of the population suffer fromurolithiasis.However,due to variations in socio-economic status and geographic locations,the prevalence and incidence have changed in different countries or regions over the years.The research for risk factors of urinary tract stones is of predominant importance.In this review,we find the prevalence of urolithiasis is 5%-19.1% in West Asia,Southeast Asia,South Asia,aswellas somedevelopedcountries(SouthKorea and Japan),whereas,it is only 1%e8%inmost part of East Asia and North Asia.The recurrence rate ranges from 21% to 53% after 3e5 years.Calciumoxalate(75%-90%)is themost frequent component of calculi,followed by uric acid(5%-20%),calciumphosphate(6%-13%),struvite(2%-15%),apatite(1%)and cystine(0.5%-1%).The incidence of urolithiasis reaches its peak in population agedover 30 years.Males aremore likely to suffer fromurinary calculi.Because of different dietary habits or genetic background,differences of prevalence among races or nationalities also exist.Geneticmutation of specific locus may contribute to the formation of different kinds of calculi.Dietary habits(westernized dietary habits and less fluid intake),as well as climatic factors(hot temperature andmany hours of exposure to sunshine)play a crucial role in the development of stones.Other diseases,especially metabolic syndrome,may also contribute to urinary tract stones.展开更多
This study proposes a supervised learning method that does not rely on labels.We use variables associated with the label as indirect labels,and construct an indirect physics-constrained loss based on the physical mech...This study proposes a supervised learning method that does not rely on labels.We use variables associated with the label as indirect labels,and construct an indirect physics-constrained loss based on the physical mechanism to train the model.In the training process,the model prediction is mapped to the space of value that conforms to the physical mechanism through the projection matrix,and then the model is trained based on the indirect labels.The final prediction result of the model conforms to the physical mechanism between indirect label and label,and also meets the constraints of the indirect label.The present study also develops projection matrix normalization and prediction covariance analysis to ensure that the model can be fully trained.Finally,the effect of the physics-constrained indirect supervised learning is verified based on a well log generation problem.展开更多
Predicting essential proteins is crucial for discovering the process of cellular organization and viability.We propose biased random walk with restart algorithm for essential proteins prediction,called BRWR.Firstly,th...Predicting essential proteins is crucial for discovering the process of cellular organization and viability.We propose biased random walk with restart algorithm for essential proteins prediction,called BRWR.Firstly,the common process of practice walk often sets the probability of particles transferring to adjacent nodes to be equal,neglecting the influence of the similarity structure on the transition probability.To address this problem,we redefine a novel transition probability matrix by integrating the gene express similarity and subcellular location similarity.The particles can obtain biased transferring probabilities to perform random walk so as to further exploit biological properties embedded in the network structure.Secondly,we use gene ontology(GO)terms score and subcellular score to calculate the initial probability vector of the random walk with restart.Finally,when the biased random walk with restart process reaches steady state,the protein importance score is obtained.In order to demonstrate superiority of BRWR,we conduct experiments on the YHQ,BioGRID,Krogan and Gavin PPI networks.The results show that the method BRWR is superior to other state-of-the-art methods in essential proteins recognition performance.Especially,compared with the contrast methods,the improvements of BRWR in terms of the ACC results range in 1.4%–5.7%,1.3%–11.9%,2.4%–8.8%,and 0.8%–14.2%,respectively.Therefore,BRWR is effective and reasonable.展开更多
Organic chemistry is undergoing a major paradigm shift,moving from a labor-intensive approach to a new era dominated by automation and artificial intelligence(AI).This transformative shift is being driven by technolog...Organic chemistry is undergoing a major paradigm shift,moving from a labor-intensive approach to a new era dominated by automation and artificial intelligence(AI).This transformative shift is being driven by technological advances,the ever-increasing demand for greater research efficiency and accuracy,and the burgeoning growth of interdisciplinary research.AI models,supported by computational power and algorithms,are drastically reshaping synthetic planning and introducing groundbreaking ways to tackle complex molecular synthesis.In addition,autonomous robotic systems are rapidly accelerating the pace of discovery by performing tedious tasks with unprecedented speed and precision.This article examines the multiple opportunities and challenges presented by this paradigm shift and explores its far-reaching implications.It provides valuable insights into the future trajectory of organic chemistry research,which is increasingly defined by the synergistic interaction of automation and AI.展开更多
We discover a new wave localization mechanism in a periodic wave system,which can produce a novel type of flat band and is distinct from the known localization mechanisms,i.e.,Anderson localization and flat band latti...We discover a new wave localization mechanism in a periodic wave system,which can produce a novel type of flat band and is distinct from the known localization mechanisms,i.e.,Anderson localization and flat band lattices.The first example we give is a designed electron waveguide(EWG)on 2DEG with special periodic confinement potential.Numerical calculations show that,with proper confinement geometry,electrons can be completely localized in an open waveguide.We interpret this flat band localization(FBL)phenomenon by introducing the concept of self-localized orbitals.Essentially,each unit cell of the waveguide is equivalent to an artificial atom,where the self-localized orbital is a special eigenstate with unique spatial distribution.These self-localized orbitals form the flat bands in the waveguide.Such self-localized orbital induced FBL is a general phenomenon of wave motion,which can arise in any wave systems with carefully engineered boundary conditions.We then design a metallic waveguide(MWG)array to illustrate that similar FBL can be readily realized and observed with electromagnetic waves.展开更多
Deep learning techniques for solving elliptic interface problems have gained significant attentions.In this paper,we introduce a hybrid residual and weak form(HRW)loss aimed at mitigating the challenge of model traini...Deep learning techniques for solving elliptic interface problems have gained significant attentions.In this paper,we introduce a hybrid residual and weak form(HRW)loss aimed at mitigating the challenge of model training.HRW utilizes the functions residual loss and Ritz method in an adversary-system,which enhances the probability of jumping out of the local optimum even when the loss landscape comprises multiple soft constraints(regularization terms),thus improving model’s capability and robustness.For the problem with interface conditions,unlike existing methods that use the domain decomposition,we design a Pre-activated ResNet of ResNet(PRoR)network structure employing a single network to feed both coordinates and corresponding subdomain indicators,thus reduces the number of parameters.The effectiveness and improvements of the PRoR with HRW are verified on two-dimensional interface problems with regular or irregular interfaces.We then apply the PRoR with HRW to solve the size-modified Poisson-Boltzmann equation,an improved dielectric continuum model for predicting the electrostatic potentials in an ionic solvent by considering the steric effects.Our findings demonstrate that the PRoR with HRW accurately approximates solvation free-energies of three proteins with irregular interfaces,showing the competitive results compared to the ones obtained using the finite element method.展开更多
In this paper,we develop an efcient and accurate procedure of electromagnetic multipole decomposition by using the Lebedev and Gaussian quadrature methods to perform the numerical integration.Firstly,we briefy review ...In this paper,we develop an efcient and accurate procedure of electromagnetic multipole decomposition by using the Lebedev and Gaussian quadrature methods to perform the numerical integration.Firstly,we briefy review the principles of multipole decomposition,highlighting two numerical projection methods including surface and volume integration.Secondly,we discuss the Lebedev and Gaussian quadrature methods,provide a detailed recipe to select the quadrature points and the corresponding weighting factor,and illustrate the integration accuracy and numerical efciency(that is,with very few sampling points)using a unit sphere surface and regular tetrahedron.In the demonstrations of an isotropic dielectric nanosphere,a symmetric scatterer,and an anisotropic nanosphere,we perform multipole decomposition and validate our numerical projection procedure.The obtained results from our procedure are all consistent with those from Mie theory,symmetry constraints,and fnite element simulations.展开更多
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...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-layerstacked 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 kz 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.展开更多
Given a constitutive relation of the bianisotropic medium,it is not trivial to study how light interacts with the photonic bianisotropic structure due to the limited available means of studying electromagnetic propert...Given a constitutive relation of the bianisotropic medium,it is not trivial to study how light interacts with the photonic bianisotropic structure due to the limited available means of studying electromagnetic properties in bianisotropic media.In this paper,we study the electromagnetic properties of photonic bianisotropic structures using the finite element method.We prove that the vector wave equation with the presence of bianisotropic is self-adjoint under scalar inner product,we propose a balanced formulation of weak form in the practical implementation,which outperforms the standard formulation in finite element modeling.Furthermore,we benchmark our numerical results obtained from finite element simulation in three different scenarios.These are bianisotropy-dependent reflection and transmission of plane waves incident onto a bianisotropic slab,band structure of bianisotropic photonic crystals with valley-dependent phenomena,and the modal properties of bianisotropic ring resonators.The first two simulated results obtained from our modified weak form yield excellent agreements either with theoretical predictions or available data from the literature,and the modal properties in the last example,i.e.,bianisotropic ring resonators as a polarization-dependent optical insulator,are also consistent with the theoretical analyses.展开更多
Considerable attention has been paid recently to coherent control of plasmon resonances in metadevices for potential applications in all-optical light-with-light signal modulation and image processing.Previous reports...Considerable attention has been paid recently to coherent control of plasmon resonances in metadevices for potential applications in all-optical light-with-light signal modulation and image processing.Previous reports based on out-ofplane coherent control of plasmon resonances were established by modulating the position of a metadevice in standing waves.Here we show that destructive and constructive absorption can be realized in metallic nano-antennas through in-plane coherent control of plasmon resonances,which is determined by the distribution rule of electricalfield components of nano-antennas.We provide proof-of-principle demonstrations of plasmonic switching effects in a gold nanodisk monomer and dimer,and propose a plasmonic encoding strategy in a gold nanodisk chain.In-plane coherent control of plasmon resonances may open a new avenue toward promising applications in optical spectral enhancement,imaging,nanolasing,and optical communication in nanocircuits.展开更多
Encircling an exceptional point(EP) in a parity-time(PT) symmetric system has shown great potential for chiral optical devices,such as chiral mode switching for symmetric and antisymmetric modes.However,to our best kn...Encircling an exceptional point(EP) in a parity-time(PT) symmetric system has shown great potential for chiral optical devices,such as chiral mode switching for symmetric and antisymmetric modes.However,to our best knowledge,chiral switching for polarization states has never been reported,although chiral polarization manipulation has significant applications in imaging,sensing,communication,etc.Here,inspired by the anti-PT symmetry,we demonstrate,for the first time to our best knowledge,an on-chip chiral polarizer by constructing a polarization-coupled anti-PT symmetric system.The transmission axes of the chiral polarizer are different for forward and backward propagation.A polarization extinction ratio of over 10 dB is achieved for both propagating directions.Moreover,a telecommunication experiment is performed to demonstrate the potential applications in polarization encoding signals.It provides a novel functionality for encircling-an-EP parametric evolution and offers a new approach for on-chip chiral polarization manipulation.展开更多
The exceptional point(EP)is one of the typical properties of parity–time-symmetric systems,arising from modes coupling with identical resonant frequencies or propagation constants in optics.Here we show that in addit...The exceptional point(EP)is one of the typical properties of parity–time-symmetric systems,arising from modes coupling with identical resonant frequencies or propagation constants in optics.Here we show that in addition to two different modes coupling,a nonuniform distribution of gain and loss leads to an offset from the original propagation constants,including both real and imaginary parts,resulting in the absence of EP.These behaviors are examined by the general coupled-mode theory from the first principle of the Maxwell equations,which yields results that are more accurate than those from the classical coupled-mode theory.Numerical verification via the finite element method is provided.In the end,we present an approach to achieve lossless propagation in a geometrically symmetric waveguide array.展开更多
Optical Kerr solitons generation based on microresonators is essential in nonlinear optics.Among various soliton generation processes,the single soliton generation plays a pivotal role since it ensures rigorous mode-l...Optical Kerr solitons generation based on microresonators is essential in nonlinear optics.Among various soliton generation processes,the single soliton generation plays a pivotal role since it ensures rigorous mode-locking on each comb line whose interval equals the free spectral range(FSR)of the microresonator.Current studies show that single soliton generation is challenging due to cavity instability.Here,we propose a new method to greatly improve single soliton generation probalility in the anomalous group velocity dispersion(GVD)regime in a micro-ring resonator based on silicon nitride.The improvement is realized by introducing mode depletion through an integrated coupled flter.It is convenient to introduce controllable single mode depletion in a micro-ring resonator by adjusting the response function of a coupled flter.We show that spectral mode depletion(SMD)can signifcantly boost the single soliton generation probability.The efect of SMD on the dynamics of optical Kerr solitons generation are also discussed.The proposed method ofers a straightforward and simple way to facilitate robust single soliton generation,and will have an impact on the research development in optical Kerr soliton generation and on-chip optical frequency mode manipulation.展开更多
基金supported by 1.3.5 project for disciplines of excellence,West China Hospital,Sichuan University,China[No.ZY2016104]Central Financial Fund,Guangzhou Medical University,China[No.2010A060801016].
文摘In Asia,about 1%-19.1% of the population suffer fromurolithiasis.However,due to variations in socio-economic status and geographic locations,the prevalence and incidence have changed in different countries or regions over the years.The research for risk factors of urinary tract stones is of predominant importance.In this review,we find the prevalence of urolithiasis is 5%-19.1% in West Asia,Southeast Asia,South Asia,aswellas somedevelopedcountries(SouthKorea and Japan),whereas,it is only 1%e8%inmost part of East Asia and North Asia.The recurrence rate ranges from 21% to 53% after 3e5 years.Calciumoxalate(75%-90%)is themost frequent component of calculi,followed by uric acid(5%-20%),calciumphosphate(6%-13%),struvite(2%-15%),apatite(1%)and cystine(0.5%-1%).The incidence of urolithiasis reaches its peak in population agedover 30 years.Males aremore likely to suffer fromurinary calculi.Because of different dietary habits or genetic background,differences of prevalence among races or nationalities also exist.Geneticmutation of specific locus may contribute to the formation of different kinds of calculi.Dietary habits(westernized dietary habits and less fluid intake),as well as climatic factors(hot temperature andmany hours of exposure to sunshine)play a crucial role in the development of stones.Other diseases,especially metabolic syndrome,may also contribute to urinary tract stones.
基金partially funded by the National Natural Science Foundation of China (Grants 51520105005 and U1663208)
文摘This study proposes a supervised learning method that does not rely on labels.We use variables associated with the label as indirect labels,and construct an indirect physics-constrained loss based on the physical mechanism to train the model.In the training process,the model prediction is mapped to the space of value that conforms to the physical mechanism through the projection matrix,and then the model is trained based on the indirect labels.The final prediction result of the model conforms to the physical mechanism between indirect label and label,and also meets the constraints of the indirect label.The present study also develops projection matrix normalization and prediction covariance analysis to ensure that the model can be fully trained.Finally,the effect of the physics-constrained indirect supervised learning is verified based on a well log generation problem.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11861045 and 62162040)。
文摘Predicting essential proteins is crucial for discovering the process of cellular organization and viability.We propose biased random walk with restart algorithm for essential proteins prediction,called BRWR.Firstly,the common process of practice walk often sets the probability of particles transferring to adjacent nodes to be equal,neglecting the influence of the similarity structure on the transition probability.To address this problem,we redefine a novel transition probability matrix by integrating the gene express similarity and subcellular location similarity.The particles can obtain biased transferring probabilities to perform random walk so as to further exploit biological properties embedded in the network structure.Secondly,we use gene ontology(GO)terms score and subcellular score to calculate the initial probability vector of the random walk with restart.Finally,when the biased random walk with restart process reaches steady state,the protein importance score is obtained.In order to demonstrate superiority of BRWR,we conduct experiments on the YHQ,BioGRID,Krogan and Gavin PPI networks.The results show that the method BRWR is superior to other state-of-the-art methods in essential proteins recognition performance.Especially,compared with the contrast methods,the improvements of BRWR in terms of the ACC results range in 1.4%–5.7%,1.3%–11.9%,2.4%–8.8%,and 0.8%–14.2%,respectively.Therefore,BRWR is effective and reasonable.
基金supported by the National Natural Science Foundation of China(22071004,21933001 and 22150013)
文摘Organic chemistry is undergoing a major paradigm shift,moving from a labor-intensive approach to a new era dominated by automation and artificial intelligence(AI).This transformative shift is being driven by technological advances,the ever-increasing demand for greater research efficiency and accuracy,and the burgeoning growth of interdisciplinary research.AI models,supported by computational power and algorithms,are drastically reshaping synthetic planning and introducing groundbreaking ways to tackle complex molecular synthesis.In addition,autonomous robotic systems are rapidly accelerating the pace of discovery by performing tedious tasks with unprecedented speed and precision.This article examines the multiple opportunities and challenges presented by this paradigm shift and explores its far-reaching implications.It provides valuable insights into the future trajectory of organic chemistry research,which is increasingly defined by the synergistic interaction of automation and AI.
基金supported by the National Natural Science Foundation of China (Grant Nos.11874160,12141401,and 11534001)the National Key Research and Development Program of China (No.2017YFA0403501)the Fundamental Research Funds for the Central Universities (HUST:2017KFYXJJ027).
文摘We discover a new wave localization mechanism in a periodic wave system,which can produce a novel type of flat band and is distinct from the known localization mechanisms,i.e.,Anderson localization and flat band lattices.The first example we give is a designed electron waveguide(EWG)on 2DEG with special periodic confinement potential.Numerical calculations show that,with proper confinement geometry,electrons can be completely localized in an open waveguide.We interpret this flat band localization(FBL)phenomenon by introducing the concept of self-localized orbitals.Essentially,each unit cell of the waveguide is equivalent to an artificial atom,where the self-localized orbital is a special eigenstate with unique spatial distribution.These self-localized orbitals form the flat bands in the waveguide.Such self-localized orbital induced FBL is a general phenomenon of wave motion,which can arise in any wave systems with carefully engineered boundary conditions.We then design a metallic waveguide(MWG)array to illustrate that similar FBL can be readily realized and observed with electromagnetic waves.
文摘Deep learning techniques for solving elliptic interface problems have gained significant attentions.In this paper,we introduce a hybrid residual and weak form(HRW)loss aimed at mitigating the challenge of model training.HRW utilizes the functions residual loss and Ritz method in an adversary-system,which enhances the probability of jumping out of the local optimum even when the loss landscape comprises multiple soft constraints(regularization terms),thus improving model’s capability and robustness.For the problem with interface conditions,unlike existing methods that use the domain decomposition,we design a Pre-activated ResNet of ResNet(PRoR)network structure employing a single network to feed both coordinates and corresponding subdomain indicators,thus reduces the number of parameters.The effectiveness and improvements of the PRoR with HRW are verified on two-dimensional interface problems with regular or irregular interfaces.We then apply the PRoR with HRW to solve the size-modified Poisson-Boltzmann equation,an improved dielectric continuum model for predicting the electrostatic potentials in an ionic solvent by considering the steric effects.Our findings demonstrate that the PRoR with HRW accurately approximates solvation free-energies of three proteins with irregular interfaces,showing the competitive results compared to the ones obtained using the finite element method.
基金funded by the National Key Research and Development Program of China(No.2021YFB2800303)Innovation Project of Optics Valley Laboratory,and the National Natural Science Foundation of China(Grant No.61405067).
文摘In this paper,we develop an efcient and accurate procedure of electromagnetic multipole decomposition by using the Lebedev and Gaussian quadrature methods to perform the numerical integration.Firstly,we briefy review the principles of multipole decomposition,highlighting two numerical projection methods including surface and volume integration.Secondly,we discuss the Lebedev and Gaussian quadrature methods,provide a detailed recipe to select the quadrature points and the corresponding weighting factor,and illustrate the integration accuracy and numerical efciency(that is,with very few sampling points)using a unit sphere surface and regular tetrahedron.In the demonstrations of an isotropic dielectric nanosphere,a symmetric scatterer,and an anisotropic nanosphere,we perform multipole decomposition and validate our numerical projection procedure.The obtained results from our procedure are all consistent with those from Mie theory,symmetry constraints,and fnite element simulations.
基金supported by the Natural National Science Foundation(NSFC)(Grant No.11874026)the Research Grants Council of Hong Kong,China(Grant Nos.AoE/P-02/12 and 16304717).
文摘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-layerstacked 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 kz 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.
基金the financial support from the National Key Research and Development Program of China(No.2019YFB2203100)the National Natural Science Foundation of China(Grant No.11874026).
文摘Given a constitutive relation of the bianisotropic medium,it is not trivial to study how light interacts with the photonic bianisotropic structure due to the limited available means of studying electromagnetic properties in bianisotropic media.In this paper,we study the electromagnetic properties of photonic bianisotropic structures using the finite element method.We prove that the vector wave equation with the presence of bianisotropic is self-adjoint under scalar inner product,we propose a balanced formulation of weak form in the practical implementation,which outperforms the standard formulation in finite element modeling.Furthermore,we benchmark our numerical results obtained from finite element simulation in three different scenarios.These are bianisotropy-dependent reflection and transmission of plane waves incident onto a bianisotropic slab,band structure of bianisotropic photonic crystals with valley-dependent phenomena,and the modal properties of bianisotropic ring resonators.The first two simulated results obtained from our modified weak form yield excellent agreements either with theoretical predictions or available data from the literature,and the modal properties in the last example,i.e.,bianisotropic ring resonators as a polarization-dependent optical insulator,are also consistent with the theoretical analyses.
基金the funding support from Singapore Ministry of Education Academic Research Fund Tier 2(grant number MOE2012-T2-2-124)and Tier 3(grant number MOE2011-T3-1-005)the funding support from the National Natural Science Foundation of China(grant numbers 61675096 and 61205042)+2 种基金the Natural Science Foundation of Jiangsu Province in China(grant number BK20141393)the funding support from Agency for Science,Technology and Research(A*STAR)SERC Pharos project(grant number 1527300025)A*STAR-JCO under project number 1437C00135.
文摘Considerable attention has been paid recently to coherent control of plasmon resonances in metadevices for potential applications in all-optical light-with-light signal modulation and image processing.Previous reports based on out-ofplane coherent control of plasmon resonances were established by modulating the position of a metadevice in standing waves.Here we show that destructive and constructive absorption can be realized in metallic nano-antennas through in-plane coherent control of plasmon resonances,which is determined by the distribution rule of electricalfield components of nano-antennas.We provide proof-of-principle demonstrations of plasmonic switching effects in a gold nanodisk monomer and dimer,and propose a plasmonic encoding strategy in a gold nanodisk chain.In-plane coherent control of plasmon resonances may open a new avenue toward promising applications in optical spectral enhancement,imaging,nanolasing,and optical communication in nanocircuits.
基金National Natural Science Foundation of China(61805090, 62075075)National Key Research and Development Project of China (2018YFB2201901)。
文摘Encircling an exceptional point(EP) in a parity-time(PT) symmetric system has shown great potential for chiral optical devices,such as chiral mode switching for symmetric and antisymmetric modes.However,to our best knowledge,chiral switching for polarization states has never been reported,although chiral polarization manipulation has significant applications in imaging,sensing,communication,etc.Here,inspired by the anti-PT symmetry,we demonstrate,for the first time to our best knowledge,an on-chip chiral polarizer by constructing a polarization-coupled anti-PT symmetric system.The transmission axes of the chiral polarizer are different for forward and backward propagation.A polarization extinction ratio of over 10 dB is achieved for both propagating directions.Moreover,a telecommunication experiment is performed to demonstrate the potential applications in polarization encoding signals.It provides a novel functionality for encircling-an-EP parametric evolution and offers a new approach for on-chip chiral polarization manipulation.
基金National Natural Science Foundation of China(NSFC)(11274083,61405067)Guandong Natural Science Foundation(2015A030313748)Shenzhen Municipal Science and Technology Plan(JCYJ20150513151706573)
文摘The exceptional point(EP)is one of the typical properties of parity–time-symmetric systems,arising from modes coupling with identical resonant frequencies or propagation constants in optics.Here we show that in addition to two different modes coupling,a nonuniform distribution of gain and loss leads to an offset from the original propagation constants,including both real and imaginary parts,resulting in the absence of EP.These behaviors are examined by the general coupled-mode theory from the first principle of the Maxwell equations,which yields results that are more accurate than those from the classical coupled-mode theory.Numerical verification via the finite element method is provided.In the end,we present an approach to achieve lossless propagation in a geometrically symmetric waveguide array.
基金supported by the National Key Research and Development Program of China(No.2019YFB2203103)。
文摘Optical Kerr solitons generation based on microresonators is essential in nonlinear optics.Among various soliton generation processes,the single soliton generation plays a pivotal role since it ensures rigorous mode-locking on each comb line whose interval equals the free spectral range(FSR)of the microresonator.Current studies show that single soliton generation is challenging due to cavity instability.Here,we propose a new method to greatly improve single soliton generation probalility in the anomalous group velocity dispersion(GVD)regime in a micro-ring resonator based on silicon nitride.The improvement is realized by introducing mode depletion through an integrated coupled flter.It is convenient to introduce controllable single mode depletion in a micro-ring resonator by adjusting the response function of a coupled flter.We show that spectral mode depletion(SMD)can signifcantly boost the single soliton generation probability.The efect of SMD on the dynamics of optical Kerr solitons generation are also discussed.The proposed method ofers a straightforward and simple way to facilitate robust single soliton generation,and will have an impact on the research development in optical Kerr soliton generation and on-chip optical frequency mode manipulation.
