分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Topological states, originated from interactions between internal degree of freedoms (like spin and orbital) in each site and crystalline symmetries, offer a new paradigm to manipulate electrons and classical waves. The accessibility of spin degree of freedom has motivated much attention on spin-related topological physics. However, intriguing topological physics related to atomic-orbital parity, another binary degree of freedom, have not been exploited since accessing approaches on atomic orbitals are not well developed. Here, we theoretically discover spectral splitting of atomic-orbital-parity-dependent second-order topological states on a designer-plasmonic Kagome metasurface, and experimentally demonstrate it by exploiting the easy controllability of metaatoms. Unlike previous demonstrations on Hermitian higher-order topological insulators, radiative non-Hermicity of the metasurface enables far-field access into metaatomic-orbital-parity-dependent topological states with polarized illuminations. The atomic-orbital parity degree of freedom may generate more intriguing topological physics by interacting with different crystalline symmetries, and promise applications in polarization-multiplexing topological lasing and quantum emitters.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Metasurface has recently emerged as a powerful platform to engineer wave packets of free electron radiation at the mesoscale. Here, we propose that accelerating waves can be generated when moving electrons interact with an array of bianisotropic meta-atoms. By changing the intrinsic coupling strength, we show full amplitude coverage and 0-to-{\pi} phase switching of Smith-Purcell radiation from bianistropic meta-atoms. This unusual property leads to the creation of Airy beams that shifts along a parabolic trajectory during propagation. Experimental implementation displays that evanescent fields bounded at slotted waveguides can be coupled into accelerating waves via Smith-Purcell radiation from a designer bianisotropic metasuface. Our results offer an alternative route towards free electron lasers with diffraction-free, self-accelerating, and self-healing beam properties.