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Edge states in heterostructures composed of two kinds of all-dielectric one-dimensional photonic crystals (1DPCs) can be utilized for narrowband filtering. However, the filtering transmittance peak, along with the photonic band gaps (PBGs) of all-dielectric 1DPC, will shift toward short wavelengths (blueshift) as the incident angle increases. In this letter, we investigate the filtering property of the heterostructure composed of an all-dielectric 1DPC and a 1DPC containing hyperbolic metamaterials (HMMs). For the 1DPC containing HMMs, the PBG can be designed to be redshifted under TM polarization. Based on these two kinds of PBGs with different angledependent properties, omnidirectional filtering at a fixed wavelength range can be realized under TM polarization. This omnidirectional filter can be utilized for all-angle phase matching in coherent nonlinear optical process and angle-insensitive Rabi splitting.

As one of the most attractive non-radiative power transfer mechanisms without cables, efficient magnetic resonance wireless power transfer (WPT) in the near field has been extensively developed in recent years, and promoted a variety of practical applications, such as mobile phones, medical implant devices and electric vehicles. However, the physical mechanism behind some key limitations of the resonance WPT, such as frequency splitting and size-dependent efficiency, is not very clear under the widely used circuit model. Here, we review the recently developed efficient and stable resonance WPT based on non-Hermitian physics, which starts from a completely different avenue (utilizing loss and gain) to introduce novel functionalities to the resonance WPT. From the perspective of non-Hermitian photonics, the coherent and incoherent effects compete and coexist in the WPT system, and the weak stable of energy transfer mainly comes from the broken phase associated with the phase transition of parity–time symmetry. Based on this basic physical framework, some optimization schemes are proposed, including using nonlinear effect, using bound states in the continuum, or resorting to the system with high-order parity-time symmetry. Moreover, the combination of non-Hermitian physics and topological photonics in multi-coil system also provides a versatile platform for long-range robust WPT with topological protection. Therefore, the non-Hermitian physics can not only exactly predict the main results of current WPT systems, but also provide new ways to solve the difficulties of previous designs.

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Topological systems containing near-field or far-field couplings between unit cells have been widely investigated in quantum and classic systems. Their band structures are well explained with theories based on tight-binding or multiple scattering formalism. However, characteristics of the topology of the bulk bands based on the joint modulation of near-field and far-field couplings are rarely studied. Such hybrid systems are hardly realized in real systems and cannot be described by neither tight-binding nor multiple scattering theories. Here, we propose a hybrid-coupling photonic topological insulator based on a quasi-1D dimerized chain with the coexistence of near-field coupling within the unit cell and far-field coupling among all sites. Both theoretical and experimental results show that topological transition is realized by introducing near-field coupling for given far-field coupling conditions. In addition to closing and reopening the bandgap, the change in near-field coupling modulates the effective mass of photonics in the upper band from positive to negative, leading to an indirect bandgap, which cannot be achieved in conventional dimerized chains with either far-field or near-field coupling only.