Since quasicrystals provide additional freedom to expand photonic bandgap, dielectric quasi-periodic sequences of broadbands become crucial for implementing low-loss omnidirectional re ectors or lters. The current major challenge is to nd an elegant scheme to construct angle-insensitive multilayer structures with fewer layer numbers. In this work, we create an appealing quasiperiodic ordering of the dielectric-reversal Fibonacci sequence to optimize the properties of omnidirectional re ectors. We have concatenated it to a periodic sequence to construct the omnidirectional re ector of hybrid multilayers with thin thickness and re ectivity above 99% over a visible scope from 436 nm to 559 nm. An ultrabroad polarization-independent omnidirectional bandgap of the relative bandwidth of 39.8% has been achieved by cascading two dielectric-reversal ordering sequences. The self-similarity of Fibonacci multilayer structures along with this characteristic quasiperiodic order guarantees the existence of perfect omnidirectional re ections at any scale. This ordering strategy of dielectric-reverse essentially differs from previous conjugate and recursion methods, which will signi cantly enrich the variety of quasiperiodic orders in theory and applied science domains.

A three-dimensional compact prototype of a photonic crystal directive antenna is constructed for beam steering and directional radiation in the microwave. Experiments demonstrate that the array of dielectric cylinders placed in a U-shape open metal cavity can be profitably exploited to act as a high-efficiency splitting directive antenna in particular modes. Highly directional radiation has been observed at the fundamental electromagnetic resonance of band edge crystal with a maximum gain of 20.73 dBi and an aperture efficiency of 49.77%. The side-lobes on the E-plane ( yoz) are almost constrained in −20 dB benefitting from the band edge lattice-induced resonance on the H-plane ( xoy), suppressing the effect of aperture diffraction, and retaining high directivity performance in space. The detected half-power beam widths on the E-plane and H-plane are 7.7° and 8.9°, respectively, agreeing well with the simulations. Different from traditional orientation approaches, the photonic crystal antenna delivers performance of high directivity gain with compact structure, facile preparation, low cost, and high efficiency, which make it suitable for spatial information transmission and modulation and offer potential applications in remote sensing and wireless communication.

Since quasicrystals provide additional freedom to expand photonic bandgap, dielectric quasi-periodic sequences of broadbands become crucial for implementing low-loss omnidirectional reflectors or filters. The current major challenge is to find an elegant scheme to construct angle-insensitive multilayer structures with fewer layer numbers. In this work, we create an appealing quasiperiodic ordering of the dielectric-reversal Fibonacci sequence to optimize the properties of omnidirectional reflectors. We have concatenated it to a periodic sequence to construct the omnidirectional reflector of hybrid multilayers with thin thickness and reflectivity above 99% over a visible scope from 436 nm to 559 nm. An ultrabroad polarization-independent omnidirectional bandgap of the relative bandwidth of 39.8% has been achieved by cascading two dielectric-reversal ordering sequences. The self-similarity of Fibonacci multilayer structures along with this characteristic quasiperiodic order guarantees the existence of perfect omnidirectional reflections at any scale. This ordering strategy of dielectric-reverse essentially differs from previous conjugate and recursion methods, which will significantly enrich the variety of quasiperiodic orders in theory and applied science domains.