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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.

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 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.

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.

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.

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.

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 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 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.

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.

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.

We designed and studied a magnetic tunable metamaterial composed of ferrite-dielectric and metallic mesh. The retrieved electromagnetic parameters and the transmission characteristic showed the composite has a double-negative regime in magnetized state. Moreover, this regime is tunable in external magnetic fields. The composite has a lower loss with minimum about −0.3 dB/mm. The simulations of the wave propagation on the interface of the composite clearly display a negative refraction. The negative indexes calculated from Snell’s law are in good agreement with the indexes retrieved from S parameters, quantitatively confirms the negative index of the composite.

We designed a two-dimensional periodic composite made of ferrite rods and metallic wires, and theoretically proved the composite in magnetized state had a tunable left-handed material (LHM) regime by its transmission properties and the retrieved effective permittivity and permeability. Further, we fabricated a sample as designed, and experimentally demonstrated the LHM regime by the sample’s abnormal transmission in bias magnetic fields. The abnormal transmission changes with the intensity of the bias magnetic field showing the frequency tunable character of the LHM regime.