分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Synchronized rotation of unit cells in a periodic structure provides a novel design perspective for manipulation of band topology. We then design a two-dimensional version of higher-order topological insulators (HOTI), by such rotation in a triangular photonic lattice with $\mathcal{C}_3$ symmetry. This HOTI supports the hallmark zero-dimensional corner states and simultaneously the one-dimensional edge states. We also find that our photonic corner states carry chiral orbital angular momenta locked by valleys, whose wavefunctions are featured by the phase vortex (singularity) positioned at the maximal Wyckoff points. Moreover, when excited by a fired source with various frequencies, the valley topological states of both one-dimensional edges and zero-dimensional corners emerge simultaneously. Extendable to higher or synthetic dimensions, our work provides access to a chiral vortex platform for HOTI realisations in the THz photonic system.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Progress on two-dimensional materials has shown that valleys, as energy extrema in a hexagonal first Brillouin zone, provides a new degree of freedom for information manipulation. Then valley Hall topological insulators supporting such-polarized edge states on boundaries were set up accordingly. In this paper, a two-dimensional valley photonic crystal composed of six tunable dielectric triangular pillars in unit cells is proposed in the photonic sense of a deformed Su-Schrieffer-Heeger (SSH) model. We reveal the vortex nature of valley states and establish the selection rules for valley polarized states. Based on the valley topology, a rhombus-shaped beam splitter waveguide is designed to verify the valley-chirality selection above. Our numerical results entail that this topologically protected edge states still maintain robust transmission at sharp corners, henceforth providing a feasible idea for valley photonic devices in THz regime.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Surface plasmons in graphene provide a compelling strategy for advanced photonic technologies thanks to their tight confinement, fast response and tunability. Recent advances in the field of all optical generation of graphene plasmons in planar waveguides offer a promising method for high speed signal processing in nanoscale integrated optoelectronic devices. Here, we use two counter propagating frequency combs with temporally synchronized pulses to demonstrate deterministic all optical generation and electrical control of multiple plasmon polaritons, excited via difference frequency generation (DFG). Electrical tuning of a hybrid graphene fibre device offers a precise control over the DFG phase matching, leading to tunable responses of the graphene plasmons at different frequencies across a broadband (0 - 50 THz) and provides a powerful tool for high speed logic operations. Our results offer insights for plasmonics on hybrid photonic devices based on layered materials and pave the way to high speed integrated optoelectronic computing circuits.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: In the known field of topological photonics, what remains less so is the breakdown effect of topological phases deteriorated by perturbation. In this paper, we investigate the variance on topological invariants for a periodic Kekul\'e medium perturbed in unit cells, which is a gyromagnetic photonic crystal holding topological phases induced by \emph{synchronized rotation} of unit cells. Two parameters for geometric and material perturbation are respectively benchmarked to pinpoint the topological degradation. Our calculation demonstrates that such a periodic perturbation easily destructs the original topological phase, and thus calls for further checkups on robustness under such unit-cell-perturbation in possible realization.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Maxwell fisheye lens was proposed to pinpoint super-resolution with the addition of wave drain and the interaction of multiple drains is theoretically predicted to improve subwavelength resolution further. In this paper we discuss the role played by port drains in optical absolute instruments, and verify by full-wave simulation that coupling nature for wave source and drain applies correctly in the picture of scanning imaging for absolute instrument. This work prospects for scanning near fields shaped from far-field wave propagation.