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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Topological Cylindrical Resonators and Optical Fibers
摘要： We propose optical resonators based on the edge modes of a cylindrical multilayer structure with nontrivial topological configuration. We calculate the field confinement and resonator dispersion by a recursive approach able to tackle with arbitrary arrangements of annular concentric layers. We apply the method to a periodical structure with Harper modulation and study the resulting cylindrical edge modes. Conventional circular optical resonators are designed exploiting the effect of total internal reflection or by Bragg structured claddings. The Bragg reflection mechanism allows to decouple the detrimental link between cavity dimensions and cavity losses present if total internal reflection is exploited. Reducing bending losses requires a large core radius, while for achieving a high quality factor small dimensions are needed. We consider photonic topological insulators, sustaining edge states, as a viable alternative for the cladding patterning to achieve optical resonators operating on protected states, immune to disorder and perturbations.
关键词： photonic topological insulators,optical resonators,topological configuration,edge modes,Harper modulation
更新于2025-09-16 10:30:52
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Microwave edge modes on a metasurface with glide symmetry
摘要： In this work we study planar metasurfaces comprised of two layers of hexagonal arrays of circular metal patches. This two-layer geometry supports a bound surface wave that propagates along the x direction. In our study, each metasurface is in?nitely periodic in one direction (x) but only a few periods wide in the orthogonal direction (y). Through experiments and modeling we ?nd evidence of a localized edge mode whose existence is dependent on the relative alignment of the two layers. This edge mode is used to guide the propagation of electromagnetic energy around both triangular and hexagonal shapes.
关键词： metasurface,electromagnetic energy propagation,glide symmetry,microwave edge modes
更新于2025-09-09 09:28:46
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Lasing in optimized two-dimensional iron-nail-shaped rod photonic crystals
摘要： We demonstrated lasing at the Γ-point band-edge (BE) modes in optimized two-dimensional iron-nail-shaped rod photonic crystals by optical pulse pumping at room temperature. As the radius of the rod increased quadratically toward the edge of the pattern, the quality factor of the Γ-point BE mode increased up to three times, and the modal volume decreased to 56% compared with the values of the original Γ-point BE mode because of the reduction of the optical loss in the horizontal direction. Single-mode lasing from an optimized iron-nail-shaped rod array with an InGaAsP multiple quantum well embedded in the nail heads was observed at a low threshold pump power of 160 μW. Real-image-based numerical simulations showed that the lasing actions originated from the optimized Γ-point BE mode and agreed well with the measurement results, including the lasing polarization, wavelength, and near-field image.
关键词： optical pulse pumping,photonic crystals,iron-nail-shaped rod,lasing,band-edge modes
更新于2025-09-04 15:30:14
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Driven conductance of an irradiated semi-Dirac material
摘要： We theoretically investigate the electronic and transport properties of a semi-Dirac material under the influence of an external time-dependent periodic driving field (irradiation) by means of Floquet theory. We explore the inelastic scattering mechanism between different sidebands, induced by irradiation, by using the Floquet scattering matrix approach. The scattering probabilities between the two nearest sidebands depend monotonically on the strength of the amplitude of the irradiation. The external irradiation induces a gap in the band dispersion which is strongly dependent on the angular orientation of momentum. Although the high-frequency limit indicates that the gap opening does not occur in an irradiated semi-Dirac material, a careful analysis of the full band structure beyond this limit reveals that a gap opening indeed appears for higher values of momentum (away from the Dirac point). Furthermore, the angular-dependent dynamical gap is also present and cannot be captured within the high-frequency approximation. The contrasting features of an irradiated semi-Dirac material, in comparison with irradiated graphene, can be probed via the behavior of conductance. The latter exhibits the appearance of nonzero conductance dips due to the gap opening in the Floquet band spectrum. Moreover, by considering a nanoribbon geometry of such a material, we also show that it can host a pair of edge modes which are fully decoupled from the bulk, which is in contrast to the case of a graphene nanoribbon where the edge modes are coupled to the bulk. We also investigate whether, if the nanoribbon of this material is exposed to the external irradiation, decoupled edge modes penetrate into the bulk.
关键词： Floquet theory,edge modes,semi-Dirac material,conductance,irradiation
更新于2025-09-04 15:30:14