Bound states in the continuum(BICs)open up a unique avenue of enhancing light–matter interactions due to their extreme field confinement and infinite quality(Q)factors.Although tremendous progress has been made in th...Bound states in the continuum(BICs)open up a unique avenue of enhancing light–matter interactions due to their extreme field confinement and infinite quality(Q)factors.Although tremendous progress has been made in the past 10 years,the majority of previous works focused on either a single BIC or dual BICs.In this work,we present both theoretical investigation and experimental demonstration on multiple BICs in a photonic crystal slab with a hexagonal lattice.All of these BICs at Γ-point can be categorized as symmetry-protected(SP)BICs.Furthermore,two BICs belong to merging BICs with topological charges q=−2.Breaking the structural symmetry will split these BICs with q=−2 into two accidental BICs with q=−1.While the other two are different from the former two,the Q-factors of both modes at the Γ-point retain a stably ultrahigh value(Q>10^(8))when the circular hole is transformed into a rotated elliptical hole with different size ratios of semi-long and semi-short axes.In addition,the Q-factors of the latter two BICs decrease rapidly with k_(x),indicating that the quasi-BICs become accessible at an ultra-small incident angle.We also show that the Q-factors of the former two BICs exhibit different dependence on the asymmetry parameters,suggesting a viable way of realizing high-Q resonances at multi-wavelengths.Finally,we presented experimental demonstration of four high-Q quasi-BICs at four different wavelengths in the near infrared by fabricating a series of photonic crystal slabs made of rotated elliptical holes and characterizing their reflection spectra.We showed that most of the measured Q-factors are above 1000 for four quasi-BICs,and the highest one can reach 16,764.Our results may find promising applications in sum-frequency generation,four-wave mixing,multiband sensing,lasing,etc.展开更多
Efficient exploration and understanding of an autonomous driving system’s capabilities and functional boundaries are crucial for ensuring safety performance.This paper offers a comprehensive examination of safety ver...Efficient exploration and understanding of an autonomous driving system’s capabilities and functional boundaries are crucial for ensuring safety performance.This paper offers a comprehensive examination of safety verification and test case generation for autonomous driving function stacks,enhancing their safety and reliability.Firstly,we introduce a holistic approach that synergizes operational flow-oriented Hazard and Operability Study(HAZOP)with cascaded System-Theoretic Process Analysis(STPA)processes.Secondly,we propose a test case generation procedure that begins with an expansion to discrete parameters using tree search,followed by heterogeneous sampling in the continuous parameter space.Additionally,this paper features a real-world case study with WATonoBus,showcasing the practicality and effectiveness of the proposed methods in securing autonomous vehicles safe operation in complex urban settings.Our findings make a substantial contribution to the autonomous vehicle safety field,offering critical insights for ongoing research and development in this rapidly advancing area.展开更多
Achieving spatiotemporal control of light at high speeds presents immense possibilities for various applications in communication,computation,metrology,and sensing.The integration of subwavelength metasurfaces and opt...Achieving spatiotemporal control of light at high speeds presents immense possibilities for various applications in communication,computation,metrology,and sensing.The integration of subwavelength metasurfaces and optical waveguides offers a promising approach to manipulate light across multiple degrees of freedom at high speed in compact photonic integrated circuit(PIC)devices.Here,we demonstrate a gigahertz-rate-switchable wavefront shaping by integrating metasurface,lithium niobate on insulator photonic waveguides,and electrodes within a PIC device.As proofs of concept,we showcase the generation of a focus beam with reconfigurable arbitrary polarizations,switchable focusing with lateral focal positions and focal length,orbital angular momentum light beams as well as Bessel beams.Our measurements indicate modulation speeds of up to the gigahertz rate.This integrated platform offers a versatile and efficient means of controlling the light field at high speed within a compact system,paving the way for potential applications in optical communication,computation,sensing,and imaging.展开更多
基金National Key Research and Development Program of China(2019YFA0705000)National Natural Science Foundation of China(12192251,12274134,12474377)+2 种基金Science and Technology Commission of Shanghai Municipality(21DZ1101500)Shanghai Municipal Education Commission(2023ZKZD35)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)。
文摘Bound states in the continuum(BICs)open up a unique avenue of enhancing light–matter interactions due to their extreme field confinement and infinite quality(Q)factors.Although tremendous progress has been made in the past 10 years,the majority of previous works focused on either a single BIC or dual BICs.In this work,we present both theoretical investigation and experimental demonstration on multiple BICs in a photonic crystal slab with a hexagonal lattice.All of these BICs at Γ-point can be categorized as symmetry-protected(SP)BICs.Furthermore,two BICs belong to merging BICs with topological charges q=−2.Breaking the structural symmetry will split these BICs with q=−2 into two accidental BICs with q=−1.While the other two are different from the former two,the Q-factors of both modes at the Γ-point retain a stably ultrahigh value(Q>10^(8))when the circular hole is transformed into a rotated elliptical hole with different size ratios of semi-long and semi-short axes.In addition,the Q-factors of the latter two BICs decrease rapidly with k_(x),indicating that the quasi-BICs become accessible at an ultra-small incident angle.We also show that the Q-factors of the former two BICs exhibit different dependence on the asymmetry parameters,suggesting a viable way of realizing high-Q resonances at multi-wavelengths.Finally,we presented experimental demonstration of four high-Q quasi-BICs at four different wavelengths in the near infrared by fabricating a series of photonic crystal slabs made of rotated elliptical holes and characterizing their reflection spectra.We showed that most of the measured Q-factors are above 1000 for four quasi-BICs,and the highest one can reach 16,764.Our results may find promising applications in sum-frequency generation,four-wave mixing,multiband sensing,lasing,etc.
文摘Efficient exploration and understanding of an autonomous driving system’s capabilities and functional boundaries are crucial for ensuring safety performance.This paper offers a comprehensive examination of safety verification and test case generation for autonomous driving function stacks,enhancing their safety and reliability.Firstly,we introduce a holistic approach that synergizes operational flow-oriented Hazard and Operability Study(HAZOP)with cascaded System-Theoretic Process Analysis(STPA)processes.Secondly,we propose a test case generation procedure that begins with an expansion to discrete parameters using tree search,followed by heterogeneous sampling in the continuous parameter space.Additionally,this paper features a real-world case study with WATonoBus,showcasing the practicality and effectiveness of the proposed methods in securing autonomous vehicles safe operation in complex urban settings.Our findings make a substantial contribution to the autonomous vehicle safety field,offering critical insights for ongoing research and development in this rapidly advancing area.
基金supported by the National Key R&D Program of China(Grant No.2019YFA0705000)the National Natural Science Foundation of China(Grant Nos.12192251,12274134,12174186,and 62288101)+2 种基金the Science and Technology Commission of Shanghai Municipality(Grant No.21DZ1101500)the Shanghai Municipal Education Commission(Grant No.2023ZKZD35)the Shanghai Pujiang Program(Grant No.20PJ1403400)
文摘Achieving spatiotemporal control of light at high speeds presents immense possibilities for various applications in communication,computation,metrology,and sensing.The integration of subwavelength metasurfaces and optical waveguides offers a promising approach to manipulate light across multiple degrees of freedom at high speed in compact photonic integrated circuit(PIC)devices.Here,we demonstrate a gigahertz-rate-switchable wavefront shaping by integrating metasurface,lithium niobate on insulator photonic waveguides,and electrodes within a PIC device.As proofs of concept,we showcase the generation of a focus beam with reconfigurable arbitrary polarizations,switchable focusing with lateral focal positions and focal length,orbital angular momentum light beams as well as Bessel beams.Our measurements indicate modulation speeds of up to the gigahertz rate.This integrated platform offers a versatile and efficient means of controlling the light field at high speed within a compact system,paving the way for potential applications in optical communication,computation,sensing,and imaging.
