Corresponding to the atmospheric transmission windows of the electromagnetic spectrum in the low terahertz range,the mode coupling and dispersion characteristics of two helically corrugated waveguides(HCW)in the frequ...Corresponding to the atmospheric transmission windows of the electromagnetic spectrum in the low terahertz range,the mode coupling and dispersion characteristics of two helically corrugated waveguides(HCW)in the frequency ranges of 90 GHz-100 GHz and 260 GHz-265 GHz are studied.Through analytic calculations and numerical simulations,dispersion curves and structural parameters of the two frequency ranges waveguides are obtained.A novel method was proposed to obtain the dispersion of the HCW from the eigenwave solution using a periodic boundary condition.The HCW in a frequency range of 90 GHz-100 GHz was fabricated and its dispersion performance was measured.By comparing the measured results with the theoretical and the simulated results,the validity of the analytical and simulation method is verified.Limited to our machining capability,the dispersion of the 260 GHz-265 GHz HCW was only simulated and calculated and it was found that the results agree well with each other.展开更多
This paper presents a theory on accurately analysing the dispersion relation and the interaction impedance of electromagnetic waves propagating through a helical groove waveguide with arbitrary groove shape, in which ...This paper presents a theory on accurately analysing the dispersion relation and the interaction impedance of electromagnetic waves propagating through a helical groove waveguide with arbitrary groove shape, in which the complex groove profile is synthesized by a series of rectangular steps. By introducing the influence of high-order evanescent modes on the connection of any two neighbouring steps by an equivalent susceptance under a modified admittance matching condition, the assumption of the neglecting discontinuity capacitance in previously published analysis is avoided, and the accurate dispersion equation is obtained by means of a combination of field-matching method and admittancematching technique. The validity of this theory is proved by comparison between the measurements and the numerical calculations for two kinds of helical groove waveguides with different groove shapes.展开更多
Non-Hermitian topology provides an emergent research frontier for studying unconventional topological phenomena and developing new materials and applications.Here,we study the non-Hermitian Chern bands and the associa...Non-Hermitian topology provides an emergent research frontier for studying unconventional topological phenomena and developing new materials and applications.Here,we study the non-Hermitian Chern bands and the associated non-Hermitian skin effects in Floquet checkerboard lattices with synthetic gauge fluxes.Such lattices can be realized in a network of coupled resonator optical waveguides in two dimensions or in an array of evanescently coupled helical optical waveguides in three dimensions.Without invoking nonreciprocal couplings,the system exhibits versatile non-Hermitian topological phases that support various skin-topological effects.Remarkably,the non-Hermitian skin effect can be engineered by changing the symmetry,revealing rich non-Hermitian topological bulk-boundary correspondences.Our system offers excellent controllability and experimental feasibility,making it appealing for exploring diverse non-Hermitian topological phenomena in photonics.展开更多
文摘Corresponding to the atmospheric transmission windows of the electromagnetic spectrum in the low terahertz range,the mode coupling and dispersion characteristics of two helically corrugated waveguides(HCW)in the frequency ranges of 90 GHz-100 GHz and 260 GHz-265 GHz are studied.Through analytic calculations and numerical simulations,dispersion curves and structural parameters of the two frequency ranges waveguides are obtained.A novel method was proposed to obtain the dispersion of the HCW from the eigenwave solution using a periodic boundary condition.The HCW in a frequency range of 90 GHz-100 GHz was fabricated and its dispersion performance was measured.By comparing the measured results with the theoretical and the simulated results,the validity of the analytical and simulation method is verified.Limited to our machining capability,the dispersion of the 260 GHz-265 GHz HCW was only simulated and calculated and it was found that the results agree well with each other.
基金Project supported in part by the National Natural Science Foundation of China （Grant Nos 60401005 and 60532010） and the Fok Ying Tung Education Foundation（Grant No 91063）.
文摘This paper presents a theory on accurately analysing the dispersion relation and the interaction impedance of electromagnetic waves propagating through a helical groove waveguide with arbitrary groove shape, in which the complex groove profile is synthesized by a series of rectangular steps. By introducing the influence of high-order evanescent modes on the connection of any two neighbouring steps by an equivalent susceptance under a modified admittance matching condition, the assumption of the neglecting discontinuity capacitance in previously published analysis is avoided, and the accurate dispersion equation is obtained by means of a combination of field-matching method and admittancematching technique. The validity of this theory is proved by comparison between the measurements and the numerical calculations for two kinds of helical groove waveguides with different groove shapes.
文摘Non-Hermitian topology provides an emergent research frontier for studying unconventional topological phenomena and developing new materials and applications.Here,we study the non-Hermitian Chern bands and the associated non-Hermitian skin effects in Floquet checkerboard lattices with synthetic gauge fluxes.Such lattices can be realized in a network of coupled resonator optical waveguides in two dimensions or in an array of evanescently coupled helical optical waveguides in three dimensions.Without invoking nonreciprocal couplings,the system exhibits versatile non-Hermitian topological phases that support various skin-topological effects.Remarkably,the non-Hermitian skin effect can be engineered by changing the symmetry,revealing rich non-Hermitian topological bulk-boundary correspondences.Our system offers excellent controllability and experimental feasibility,making it appealing for exploring diverse non-Hermitian topological phenomena in photonics.
