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We systematically study the first- and second-order band topologies, which are tied to the pseudospin and valley degree of freedoms (DOFs), in honeycomb-kagome photonic crystals (HKPCs). We first demonstrate the quantum spin Hall phase as the first-order pseudospin-induced topology in HKPCs by observing the partial pseudospin-momentum locked edge states. By employing the topological crystalline index, we also discover the multiple corner states emerging in the hexagon-shaped supercell as the manifestation of the second-order pseudospin-induced topology in HKPCs. Next, by gapping the Dirac points, a lower band gap associated with the valley DOF emerges, in which the valley-momentum locked edge states are observed as the first-order valley-induced topology. Such HKPCs without inversion symmetry are proved to be Wannier-type second-order topological insulators, which manifested with valley-selective corner states. Additionally, we also discuss the symmetry breaking effect on pseudospin-momentum locked edge states. Our work realizes both pseudospin-induced and valley-induced topologies in a higher-order manner and thus provides more flexibility in manipulating electromagnetic waves, which may find potential applications in topological routings.

Most natural and artificial materials have crystalline structures from which abundant topological phases emerge1–6. However, the bulk–edge correspondence—which has been widely used in experiments to determine the band topology from edge properties—is inadequate in discerning various topological crystalline phases7–16, leading to challenges in the experimental classification of the large family of topological crystalline materials4–6. It has been theoretically predicted that disclinations—ubiquitous crystallographic defects—can provide an effective probe of crystalline topology beyond edges17–19, but this has not yet been confirmed in experiments. Here we report an experimental demonstration of bulk–disclination correspondence, which manifests as fractional spectral charge and robust bound states at the disclinations. The fractional disclination charge originates from the symmetry-protected bulk charge patterns—a fundamental property of many topological crystalline insulators (TCIs). Furthermore, the robust bound states at disclinations emerge as a secondary, but directly observable, property of TCIs. Using reconfigurable photonic crystals as photonic TCIs with higher-order topology, we observe these hallmark features via pump–probe and near-field detection measurements. It is shown that both the fractional charge and the localized states emerge at the disclination in the TCI phase but vanish in the trivial phase. This experimental demonstration of bulk–disclination correspondence reveals a fundamental phenomenon and a paradigm for exploring topological materials. It is experimentally shown that topological states exist at crystallographic defects in the bulk and that disclination defects trap fractional charges characteristic of topological crystalline insulators.

A highly feasible approach to achieve a broadband radar cross section (RCS) reduction using a simple magnetic metasurface is presented. A magnetic absorbing material (MAM) with high permittivity and magnetic loss is introduced into the metasurface design instead of the more common dielectric material to considerably reduce its thickness. The metasurface is composed of an optimized two-dimensional array of MAM meta-atoms and a metal plate in back. The meta-atoms share a simple square ring shape but with variable geometrical parameters, forming strong absorption in different frequency bands with large reflection phase differences. By hybridizing the absorption and phase-cancelation technique, a 10-dB RCS reduction from 3.4 to 18 GHz is achieved at a thickness of only 4 mm. Further experimental measurements are provided to evaluate the performance. Our work provides a promising way to broaden the bandwidth of RCS reduction with low density, reduced thickness, and stable performance, which can be utilized in harsh physical and chemical environments.

Considering the operation reliability of flexible and optical electronics (FOEs) in dynamic and real-world environments, autonomous self-healing electromagnetic interference (EMI) shielding materials with high transparency, good stretchability and excellent tear-resistance are urgently required but always difficult to achieve due to the poor dynamics of their elastic substrates. Herein, we propose a facile strategy to design a highly dynamic polyurea elastomer (PDMS-MPI-HDI) featuring with ultrahigh optical transparency (>94%), ultralow elastic modulus (

A frequency selective rasober (FSR) with high-temperature-resistance, wideband radar cross section reduction (RCSR), and flat-broad transmission band is presented in this paper. It consists of three functional layers: a piece of insulation tile, scattering cancellation metasurface based on interdigitated element, and a triple-layer-coupled-resonator spatial filter frequency selective surface. At low-frequency band, the incident energy is diffused to various directions, resulting in 10 dB RCSR over 2.52-11.68 GHz with a 129% fractional bandwidth. Besides, there is a highly efficient transmission band (insertion loss < 0.595 dB) over 16.53-19.83 GHz. It is also worth mentioning that our FSR can maintain such good properties at 500°C for 5 seconds with the help of insulation tile.

We proposed a promising method to achieve phase modulation utilizing photonic crystal (PC). The broken parity and time-reversal symmetries induce intrinsic nonreciprocity. The supported one-way phase velocity which has a close relationship with biased magnetic field (BMF). Different from the most metasurfaces, only one structure is required to realize electromagnetic wave spatial distributions by adjusting each cell’s BMF. As an application, a deflector with only one column shows obviously nonreciprocity accompanied with magnetically tunable deflection angle. We further designed a flat lens and an axicon under different applied BMF distributions. Such phase modulation by PC provides a new flexible way to realize phase modulation, which can reduce difficulties in design and fabrication.

We theoretically and experimentally demonstrate that magnetic plasmonic gradient metasurfaces (GMSs) can convert a spatially propagating wave to a one-way edge state or vice versa with high efficiency. Consisting of an array of ferrite rods with a rotation gradient introduced to the rod dimers in the unit cell, GMSs can covert an incident wave beam to a one-way edge state with efficiency over 77%, and almost fully radiate into free space from the one-way edge state. The phenomenon arises from the unidirectional coupling of the spatial electromagnetic wave with magnetic plasmonic GMSs, which is evidenced from the photonic band diagrams of the edge state. The one-way edge state can radiate to or be excited from air with different angles by either engineering the gradient of the GMSs or tuning the bias magnetic field. By designing magnetic plasmonic GMSs with more exquisite configurations, we can expect many more nonreciprocal properties, adding additional freedom in manipulating electromagnetic waves.

Topological insulators have unconventional gapless edge states where disorder-induced back-scattering is suppressed. In photonics, such edge states lead to unidirectional waveguides which are useful for integrated photonic circuitry. Cavity modes, another type of fundamental component in photonic chips, however, are not protected by band topology because of their lower dimensions. Here we demonstrate that concurrent wavevector space and real-space topology, dubbed as dual-topology, can lead to light-trapping in lower dimensions. The resultant photonic-bound state emerges as a Jackiw–Rebbi soliton mode localized on a dislocation in a two-dimensional photonic crystal, as proposed theoretically and discovered experimentally. Such a strongly confined cavity mode is found to be robust against perturbations. Our study unveils a mechanism for topological light-trapping in lower dimensions, which is invaluable for fundamental physics and various applications in photonics., Although topological confinement of waves to the edges is common, lower-dimensional wave confinement is scarce. Here, Li et al. demonstrate that concurrent wavevector and real-space topology can lead to a topologically protected zero-dimensional cavity mode in a two-dimensional photonic crystal.

We demonstrated a good unidirectional transmission (UT) with high transmission efficiency without breaking time-reversal symmetry both theoretically and experimentally. By adjusting the topological structure and designing the component of all-dielectric photonic crystal, an accidental degenerated Dirac point is built at Γ point. We obtained simultaneous zero permittivity and zero permeability. Truncating the PC into a bow-tie shape, we observed a total reflection in one direction but a total transmission in the opposite direction. The good agreement between the theoretical and experimental data verifies such model supports a good UT even considering the material's loss. Due to the PC's scale invariance, this kind of UT can be conveniently exploited into terahertz or optical frequency, providing a great promising application to optical communication and optical circuit.

We propose and experimentally demonstrate a frequency reconfigurable antenna using ferrite loaded half-mode substrate integrated waveguide (SIW). The antenna design is based on a SIW cavity with an embedded ferrite slab, which causes the resonant frequency of the cavity tunable under bias magnetic field. The antenna features omni-direction radiation and small size. A prototype antenna is designed and fabricated. The measurements show the tunable frequency bandwidth is over 11% covering frequencies 5.04–5.62 GHz in low bias magnetic field region, and 5% covering 4.28–4.5 GHz in high bias magnetic field region. The measurement is in good agreement with simulations. The gain of antenna is all over 1.6 dBi, and the frequency reconfiguration does not affect the radiation pattern of the antenna, providing a preferable feature for frequency reconfigurable antenna. This type of antenna may be a good candidate for practical applications such as base stations and satellites. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1365–1371, 2017

We experimentally presented electromagnetic one-way transmission in 2D magnetic photonic crystal (MPC) with only 1 Oe remnant magnetism. Such nonreciprocal edge state is independent on the degenerated point but extends from the bulk mode instead. We proved the edge state exists in both PEC and PMC boundary conditions. Distinguished from those under fully saturated magnetization, the nonreciprocal transmission in this paper requires very low, even near-zero biased magnetic field, which is flexible to implement and opens up a new avenue in nonreciprocal device design.

A modified reflective metasurface, which is constructed by replacing the metal ground of the reflective coding metasurface with a bandpass frequency-selective surface, is proposed. The metasurface has transmission and reduction of radar cross-section characteristics. This allows the metasurface to overcome the drawbacks of conventional realizations, which use lossy materials. The modified metasurface provides high-efficiency transmission in the passband of a frequency-selective surface and broadband reduction of the radar cross section in the rejection band of the frequency-selective surface. Transmission of -0.24 dB was achieved at 4.6 GHz, as well as a -15 dB reduction of radar cross section from 8.5 to 13.5 GHz. This work provides advancements in metasurface applications.

A novel reconfigurable half-mode substrate integrated waveguide antenna with broadband frequency tunability is presented in this letter. It consists of a microstrip line, a half-mode substrate integrated waveguide (HMSIW) cavity, two slots, and an inserted ferrite slab. Broadband frequency tunability is realized by increasing the biased magnetic field for the loaded ferrite from the low-field region to the high-field region. The simulation and experimental results prove the feasibility of the proposed design. The measurement results show that the frequency tuning range is more than 1160 MHz (5.07–6.23 GHz), and the peak gain is 1.41 dBi. The change of the magnetic field has little impact on radiation patterns of the antenna.

Perfect magnetic conductor (PMC) has been attracting lots of interests in both theoretical study and engineering for its remarkable applications in electromagnetic tunneling, antenna and absorber. Here we propose a scheme for wide-angle magnetically tunable PMC utilizing only ferrite at microwave frequencies. We point out the transverse magnetized ferrite operates as a good PMC at spin resonance when ignoring intrinsic loss. The electromagnetic wave normally incident on the semi-infinite ferrite is totally reflected without electric field phase change forming an antinode on the surface. Superior to the high impedance surfaces, such ferrite is intrinsically insensitive to incident angle due to the isotropic characteristic at spin resonance. The ferrite PMC is proved to be frequency tunable by biased magnetic field and have flexible structures. After considering material’s loss, the ferrite PMC also possesses good performance at low frequencies. A further study of an electric dipole antenna’s radiation enhancement is given to prove the ferrite’s PMC property.

We proposed a comprehensive scheme, combining Dallenbach layer and Salisbury screen to achieve broadband perfect absorption. We establish an equivalent circuit model to analysis and tune the impedance of designed absorber. With the Salisbury screen acting as a matching and absorbing layer, we show that broadband perfect impedance matching between air and designed absorber can be achieved by adjusting the Salisbury functional layer. The calculated reflectivity of −20 dB covers 5.8-12.1 GHz. Experimentally, the sample was fabricated by using silk-screen printing technique and the absorbing performance was measured, which has a good consistance with the design.

We propose a zero phase delay waveguide simply utilizing two parity-time (PT) photonic crystals (PCs) magnetized in opposite directions. Based on the bulk one-way phase velocity of the PCs, electromagnetic wave incident normally on such a waveguide experiences reverse phase change, which makes the outgoing wave have the same phase with the incident wave, i.e. zero phase delay. By adjusting the filling ratio of the two PCs, we can feasibly realize zero phase delay in a wide frequency range, which provides potential for practical applications.

Utilizing the transmission /reflection measurement method, we investigated the complex conductivity of conductive ink films at microwave X-band. The results show that the frequency dependence of the complex conductivity is in good agreement with the Drude model. However, the retrieved plasmon frequency ω p and the collision frequency Wt are much lower than those of metal materials. The effect of surface morphology of the films on complex conductivity was investigated. The study provides a solid foundation for the applications of conductive ink films, such as wideband absorber designs.

A novel broadband concave paper antenna is proposed for low cost and conformal applications. The new design is a three-dimensional monopole antenna. Owing to the concave flexible paper substrate, the proposed antenna is easy to integrate with the packing case or the communication product. The broadband antenna can be used in the applications covering the 0.903–2.63 GHz band, such as 2G, 3G, and WLAN. Its gain is 3.8 dBi at 0.915 GHz, 3.5 dBi at 1.0 GHz, 2.8 dBi at 1.8 GHz, and 4.8 dBi at 2.45 GHz. Experiments validate the simulated results of our antenna.

We propose a novel reconfigurable substrate-integrated waveguide (SIW) slot antenna with frequency and polarization tunability. Based on the multimode characteristic of SIW resonant cavity, the antenna works in two bands and radiates in linear or circular polarizations by tuning a crossed radiation slot. With the loading of ferrite slabs, the polarizations and operation frequencies of the antenna can be tuned by varying the bias magnetic field (BMF). The proposed design is verified by both simulations and experiments. The measurement results show that the tunable frequency range is more than 8.1% in the lower frequency band (from 8.98 to 9.74 GHz) and 5.5% in the higher frequency band (from 9.98 to 10.54 GHz). The antenna gain is more than 5.1 dBi within the frequency tuning range. The radiation pattern of the antenna is almost not affected by the changes in the BMF.

We demonstrated that non-reciprocal wave propagation could be manipulated by a magnetic rod chain under bias DC magnetic fields. Made of ferrite material YIG and designed working in the microwave X-band, the rod chain exhibited almost a total reflection when the incident wave obliquely impinged on the rod chain, but exhibited nearly a total transmission when the wave reversed its propagation direction. The non-reciprocal wave propagation was due to the non-reciprocal diffraction of the rod chain for the orders 0 and ± 1. Further, the non-reciprocal wave propagation was directly observed by using the field mapping technique. The unique non-reciprocal wave property of the magnetic rod chain provides a new way to control the flow of EM waves.

A practical method was proposed to implement the directional antenna by self-biased magnetic photonic crystals (MPC). By studying the influence of the shell’s boundary shapes and the source’s position on the antenna radiation, we designed an antenna with a good directional radiation performance by utilizing MPC in hexagonal lattice to fill a left-handed material (LHM) shell with a special shape. The implementation provides a practical way of LHM in the antenna applications.

We studied how the constitution parameters and applied bias magnetic field influence the bandwidth and frequency tunability of the one-way transmission (OWT) caused by magnetic surface plasmon resonance of the magnetic photonic crystals (MPC). We found that wide-band OWT could be obtained using ferrite rods with larger normalized radius and suppressing the bulk modes of MPC in the frequencies where the edge and bulk modes coexist. We verified that bias magnetic field tunes the frequencies of OWT but has little effects on its bandwidth by experiments, and a simple way is proposed to suppress the bulk modes by introducing air defect near the edge of the MPC and experimentally demonstrated its effectiveness. This work provides a way toward practical applications for wide-band tunable one-way devices.

Considering the combined effects of the intensity scintillation and the beam wander in the satellite-to-ground laser uplink communication system, the bit error rate (BER) performance of three modulation schemes – on–off keying (OOK), binary phase-shifted keying (BPSK), quadrature phase-shifted keying (QPSK) are investigated. In comparison with the condition in which the atmospheric turbulence is not taken into consideration, conclusions that atmospheric turbulence severely degrades the performance of the system are drawn. Based on the simulation results, the advantages of BPSK are analyzed in contrast with OOK and QPSK. Specially, when transmission power is 4 W, performance of OOK shows 18 dB impairment while performance of QPSK shows 3 dB impairment compared with BPSK under the atmospheric fluctuation. Further compared to QPSK, BPSK owns lower BER and simpler process. Considered the feasibility in communication systems, BPSK should be the most reasonable modulation scheme which can decrease the BER of systems without increasing the transmitter power among these three modulation schemes. Besides, optimum divergence angle, optimum beam radius and appropriate receiver diameter are also analyzed, which is significant in practical applications.

We present a novel approach to realize broadband frequency tunability of ferrite-loaded substrate integrated waveguide (SIW) antennas by simultaneously changing the location of ferrite slabs in the antennas (mechanical tuning) and bias magnetic fields (magnetical tuning). The proposed method is verified by the antenna designed in X-band with experiments. The measurements show that the antenna has frequency tuning range over 14.94% (9.23-10.69 GHz) and gains over 5 dBi. The radiation pattern of the antenna changes little in tunings, showing a good property for tunable antennas.

We propose an array of randomly distributed lossy scatterers to achieve broadband backscattering reduction. The array efficiently combines absorption and diffusion functionalities by using three subarrays made of ferromagnetic or dielectric scatterers based on resistive octagonal rings. The subarrays have strong absorption in different frequency bands, whereas they have different reflection phases in a wide frequency band, resulting in -10 dB backscattering reduction in a wide frequency range (from 3.15 to 18 GHz). The results are verified by experiments. Our work provides a new way to reduce backscattering in a wider frequency range and at lower frequencies.

One-way light has attracted much attention recently. They have wide range of applications, such as optical isolators and optical diodes. At present, two approaches can be used to realize the one-way light. One is one-way surface waves, which come from chiral edge states of photonic crystals [1, 2]. The other is one-way body waves, which may originate from the parity-time symmetry of a system [3, 4]. Here, we theoretically demonstrate that by breaking parity and time-reversal symmetries at the same time electromagnetic waves can self-collimate and propagate unidirectional in photonic crystals fabricated by semi-cylindrical ferrite rods in magnetized states. Self-collimated one-way body wave presents at certain unit cell configurations of the photonic crystal, and the one-way wave beam shows robustness in some way to certain kind of disorders in the wave channel. We find the propagation direction of the self-collimated one-way wave beams can be tuned using a bias magnetic field. Therefore, we can bend the self-collimated one-way body wave, which can be considered as a curved waveguide. Further, by applying the bias magnetic field in a complex configuration, the self-collimated one-way wave beam can be bent into arbitrary trajectories within the photonic crystal, providing a new avenue for controlling wave beams.

Electromagnetic (EM) topological states [1, 2] have been drawing lots of attentions in both physical and engineering field for their good performance in optical isolator, circulator, etc‥ As a resemblance of signal carrier in modern communication, the excited EM chiral edge state (CES) is immune to the impurity of transmission path without any backward scattering, providing a potential for future transoceanic communication with no require of repeaters of amplifiers. Mimicking modulation and demodulation of FDM, in this work we realize a resemble function in photonic system by constructing multi-mode CES. Different from most of the presented work with only one CES mode, in this paper we design and experimentally observed a two-mode CES. Such multi-mode CES resembles frequency division multiplexing (FDM). If we consider real space position in PC as the time and the wave vector as frequency. By designing a magnetic photonic crystal (MPC) with square lattice, we obtained eight Dirac points existing at non-high symmetry point in Brillioun zone due to mirror symmetry [3] by keeping time-reversal symmetry. It is demonstrated all Dirac points are unbuckled to open a full gap in the effect of bias magnetic field. Once the MPC is truncated by metal cladding, two-mode edge states appear inside the gap as shown. At an operating frequency, two EM waves are excited with different wavelengths (wavevector) but the same transmission direction. The experimental data verify such two-mode edge states are unidirectional and robust against the scatterings from disorders of various kinds. By introducing the Fast Fourier Transform (FFT) algorithm in EM system, we successfully obtain the band structure of CES basing on the field profile measured. Later, imitating the demodulation in communication engineering, we theoretically propose a method to eliminate one of modes by introducing two feed with same magnitude and phase but located at different positions.

One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-reversal and parity symmetries of the magnetic photonic crystals designed, we observe oblique incident space wave propagating one-way in the magnetic photonic crystals with positive or negative refraction occurring at interfaces, which can be manipulated upon the incident angle and operating frequency. Our work may offer a potential platform to realize some exotic photoelectronic and microwave devices such as one-way imaging and one-way cloaking.

We experimentally observed a photonic Chern insulator with large Chern number. Two nontrivial chiral edge states have been distinguished. By introducing two excitation probes and changing their positions, we successfully eliminate one of the modes.

We realize double zero-refractive-index material by dielectric photonic crystals (PCs) with hexagonal lattice at the frequencies near the degenerated Dirac point. We demonstrate such PC can be used as a flat lens which has matched impedance to the air and low loss. The performance of the lens is verified by good near-field imaging both theoretically and experimentally. Further, the zero-refractive-index PC is extended to the plane wave generator and concave lens at terahertz frequencies. Our design provides potential for practical applications of wave manipulation.

We experimentally studied the frequency dependent complex permittivity e and permeability μ of composite composed of carbonyl iron powder (CIP) and epoxy resin in the frequency range 1–18 GHz. We found that the intrinsic e and μ of CIP extracted from the measured e and μ of composites follow the classical Maxwell equations and the Landau–Lifshitz–Gilbert (LLG) equation, respectively. The dependences of e and μ of composites on the volume fraction of CIP (vf CIP ) were investigated using the two-exponent phenomenological percolation equation (TEPPE). We found that the TEPPE can fit the experimental results very well. Comparing the results of percolation parameters derived by experimental data at different frequencies, we show that the TEPPE is frequency independent for the composites at microwave frequencies. The results also show that the e and μ spectrums of composites with definite vf CIP can be correctly calculated by combining the TEPPE with the theoretical models of intrinsic e and μ .

We introduce the application of magnetic artificial materials in the design of directional antenna. Two ways to use magnetic materials to enhance the directional radiation of sources are demonstrated. One way is the left-handed materials (LHMs) and the other is electromagnetic bandgap (EBG) structures. In both cases, the radiation of the antenna exhibits good radiation performance but the underlying mechanisms are different. The special advantage of the antenna designed by LHM is its lower radar cross section, whereas the one by magnetic EBG structures is the frequency tunability.

To achieve a unidirectional transmission waveguide with miniature dimensions and flexible geometry, we propose a self-guided unidirectional waveguide composed of a chain of gyromagnetic rods. Two configurations of the waveguides were demonstrated. One is of a zigzag chain form, the other is a straight-line chain. These two types of waveguides have very wide one-way edge mode bandwidths. The simulated and experimental results illustrate their extraordinary wideband one-way transmission characteristics. They can also be expected to function as flexible platforms for practical applications because of their thin transverse dimensions and robustness to bending.

A new type of frequency reconfigurable antenna, the ferrite slab loaded substrate integrated waveguide (SIW) antenna, is proposed. Due to the loaded ferrite, the operating frequency of the antenna can be tuned in a wide frequency range by bias magnetic field and the position of ferrite slab in the antenna. Three example reconfigurable SIW antennas are designed, fabricated and measured. The experimental results prove the frequency tunablity of the antennas and show the tunable range could be much larger than that of electronic reconfigurable antennas. The radiation pattern and gain of the antenna characterize their good radiation performance which may be promising in wireless communication systems.

At the zigzag edge of a magnetic photonic crystal with honeycomb lattice, the nonreciprocal surface modes (NSMs) could appear below the magnetic surface plasmon (MSP) frequency. The NSMs possess very flat slopes outside the light line, which is strikingly different from the nearly linear dispersion curve just above the MSP frequency and results in strong confinement and enhancement of the electromagnetic field. Particularly, an enhancement over 100 times in magnetic field is achieved because of the strong magnetic response arising from the MSP resonance. In addition, the branch of double-valued NSM dispersion curve provides zero group velocity away from the Brillouin zone boundary.

We present an experimental demonstration of self-guiding electromagnetic edge states existing along the zigzag edge of a honeycomb magnetic photonic crystal. These edge states are shown to possess unidirectional propagation characteristics that are robust against various types of defects and obstacles. In particular, they allow for the unidirectional transport of electromagnetic energy without requiring an ancillary cladding layer.

Magnetic tunable left-handed material composed of ferrite-dielectric and metallic mesh is proposed and verified. We discuss the variation of electromagnetic parameters due to the change of three flexible geometry parameters: the lattice constant, the line width of the mesh, and the thickness of dielectric. The mesh affects the permittivity but does not affect the frequency range of negative permeability, while the thickness of dielectric will affect both permittivity and permeability. The topology and the external magnetic field both affect the central frequency and bandwidth of the left-handed region.

Based on the analysis of working mechanism of microstrip coupler, a new microstrip coupler with EBG structure has been proposed. The coupling degree of the new coupler is greatly enhanced due to the EBG structure. The coupler is demonstrated by the experiment and the measured coupling coefficient is in good agreement with the simulation results. The new coupler has the advantages of strong coupling and broadband working frequencies compared with traditional microstrip couplers. Meanwhile the coupler is with simple geometry and convenience for fabrication.

There exist two types of electromagnetic (EM) one-way edge states in magnetic photonic crystal (MPC). One is associated with photonic band gap (PBG) relevant to Bragg scattering, while the other is associated with PBG originating from magnetic surface plasmon resonance. Both support robust unidirectional wave transmission, but each with relatively limited operating bandwidth. By optimizing the lattice spacing and filling ratio of MPC as well as tuning the external static biasing magnetic field, we are able to fuse the two types of EM one-way edge states together and therefore achieve broadband one-way transmission. The operating bandwidth could be about 4 GHz in a microwave regime; this is much larger than that based on either type, providing a way towards the practical applications of unidirectional wave propagation.

In a ground-to-satellite communication system with a preset EDFA, the EDFA's performance will be affected by space environment. With 250 Gy radiation, the EDFA's gain decreases by 2 dB from 19.97 dB at 20 °C. The BER increases by 2.5 orders of magnitude from 10(-10), and increases more with more radiation. The situation aggravates when the temperature rises by 73 °C. The laser's divergence-angle and transmitter radius have optimal values to make the lowest BER and increasing receiver diameter makes lower BERs, so setting these parameters with appropriate values will compensate the degradation caused by EDFA.

To better understand the resonance modes caused by the interelement couplings in the building block of metamaterials, we propose a circuit model for the hybrid resonance modes of paired split ring resonators. The model identifies the electromagnetic coupling between the paired rings by electric and magnetic coupling networks and well explains the variation of hybrid resonance modes with respect to the distance and the twist angle between the rings. The predictions of our model are further proved by experiments.

We experimentally demonstrate that electromagnetic waves in the waveguide comprising gyromagnetic photonic crystals (GMPCs) and a metal cladding are robust one-way slow waves in the frequency range of the chiral edge states of GMPC. Measured with phase shift technique in microwave regime, the group velocity of the wave could be one order of magnitude smaller than the speed of light with group index up to 15.6. The one-way wave with much slower group velocity is shown by retailoring the waveguide further. This waveguide provides a potential way to realize robust slow-light transmission lines in electromagnetic or optical systems.

We present experimental demonstrations that the material consists of self-biased Sr-ferrite rods is the lower loss left-handed material (LHM). Clear negative refractions are observed in refraction experiments with the wedge shaped samples made from this material, and negative effective refractive index n = −1 is measured. The attenuation of the sample is about 0.55 dB/cm obtained from transmission measurements much lower than other known LHMs. Our configuration avoids the bias magnetic fields required for LHMs made of soft magnetic materials and extremely high permittivity needed for making LHMs with purely dielectrics, which greatly improves its impedance mismatch with the air.

It is experimentally demonstrated that within the photonic band gap induced by magnetic surface plasmon (MSP) resonance in a honeycomb magnetic photonic crystal, there can exist self-guiding electromagnetic chiral edge states whose dispersion curves are insensitive to the surface morphology when the system is truncated. The unique characteristic of the MSP induced edge states enables flexible design of robust unidirectional subwavelength waveguides that contain bends at various angles, providing an alternative way for manipulating electromagnetic waves at subwavelength scales.