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This paper presents a novel polarization-reconfigurable antenna based on the combination of circularly polarized (CP) modes, which is capable of changing its polarization states among arbitrary linear polarizations (LPs), left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP). A truncated square patch with two isolated aperture-coupling feeds is used as radiation element operating at 2.45 GHz, which can operate in two orthogonal CP modes with low crosstalk. By exciting one of the two feeding microstrip lines, LHCP or RHCP mode can be independently generated. Meanwhile, by simultaneously exciting the two feeding microstrip lines with identical amplitudes but with different initial phases, LP mode with polarization plane oriented in any desired azimuth direction can be obtained. The simulated and measured peak gain of the proposed antenna remains at about 6.8 dBi at 2.45 GHz and the impedance matching bandwidth ranging from 2.25 to 2.60 GHz is fully overlapped for all the polarization states. Experimental results show a good performance of the proposed antenna.

In this paper, the properties of one-dimensional (1D) photonic crystals (PCs) composed of the semiconductor (GaAs) and dielectric layers are theoretically investigated by the transfer matrix method (TMM). The absorption of semiconductor layers is investigated theoretically. Due to the magneto-optical Voigt effect, the dielectric constant of the semiconductor is modified differently in different modes and frequency ranges. If the frequency range of the incident wave is larger than the plasma frequency, TE and TM modes of the incident wave will be absorbed in a wide incident angle. TM wave will be absorbed but TE wave will be reflected while the frequency range is less than the plasma frequency. The absorption of semiconductor can also be tuned by varying the external magnetic field. The proposed PCs have a reconfigurable application to design a tunable omnidirectional absorber and mode splitter at same time.

In this paper, the magneto-optical Voigt effects in surface plasmon modes and anisotropic photonic band gaps (PBGs) of the three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) with face-centered-cubic lattices are theoretically investigated based on the modified plane wave expansion (PWE) method, which are the homogeneous Te (tellurium) spheres immersed in the homogeneous magnetized plasma background, as the mixed polarized modes are considered. The more general condition is considered, and the anisotropic PBGs are not only for the extraordinary and ordinary modes but also for mixed polarized modes. The equations for computing such anisotropic PBGs are theoretically deduced. Theoretical simulations show that the anisotropic PBGs and a flatbands region can be observed in the dispersive curve. Compared to the similar 3D MPPCs containing the isotropic dielectric or uniaxial material spheres, the larger PBGs can be obtained as the extraordinary axis of the inserted uniaxial material is along the Г–H symmetry line although the region of flatbands is also different. However, the relative bandwidths of PBGs for such two cases are almost the same. The interesting properties of surface plasmon modes can also be found, which are that the upper edge of flatbands region cannot be tuned by the filling factor but can almost linearly increase on increasing the plasma frequency and plasma cyclotron frequency (the external magnetic field), respectively. The effects of the filling factor, plasma frequency and plasma cyclotron frequency on the anisotropic PBGs are investigated in detail, respectively. Theoretical calculations also show that such PBGs can be manipulated by the parameters as mentioned above.

In this paper, the dispersive properties and switching state of three-dimensional (3D) photonic crystals (PCs) with face-centered-cubic lattices, which are composed of core anisotropic dielectric (tellurium) spheres surrounded by non-magnetized plasma shells inserted in the air, are theoretically investigated in detail based on a modified plane wave expansion method. The equations for calculating the band structures for such 3D PCs are deduced. Our analyses show that the proposed double-shell structures can produce the complete photonic band gaps (PBGs) which can work as the optical switching by manipulating the radius of core dielectric sphere and the plasma frequency. However, the switching state of PCs cannot be tuned by the thickness of the plasma shell and plasma collision frequency as the radius of the core dielectric sphere is certain. Numerical simulations also demonstrate that a flatbands region, and the stop band gaps (SBGs) in the (1 0 0) and (1 1 1) directions which are above the flatbands region can be achieved. The SBGs in the (1 0 0) and (1 1 1) directions can also be tuned by the parameters as mentioned above. There is also a threshold value for the thickness of plasma shell, which makes the band structures of such 3D PCs with double-shell structures to be similar to those obtained from the same PCs containing the pure plasma spheres. In this condition, the dielectric function of inserted core sphere will not affect the band structures. It means that the PBGs can be achieved by replacing the pure plasma spheres with such double-shell structures to make fabrication possible and save the material in the realization. It is also noted that the flatbands region is determined by the existence of surface plasmon modes, and the upper edge of flatbands region does not depend on the topology of lattice. The proposed 3D PCs with double-shell structures offer a novel way to realize the tunable optical switching.

In this paper, the properties of omnidirectional photonic band gaps (OBGs) in two-dimensional plasma photonic crystals (2D PPCs) for two novel configurations with triangular lattices are theoretically investigated by the modified plane wave expansion method in detail as the off-plane incident wave vector is considered, which are composed of the nomagnetized plasma cylinders inserted into the homogeneous and isotropic dielectric background. The computed results reveal that the proposed two new configurations have the advantage of obtaining the larger OBGs compared to the conventional configuration because the symmetry of 2D PPCs is broken by periodically inserted different sizes of plasma cylinders or connected the embedded plasma cylinders with thin veins. The analysis results show that the bandwidths of OBGs can be tuned obviously by changing geometric parameters of such two PCs structures. Those theoretical results may open a new scope to design the omnidirectional reflector or mirror based on the 2D PPCs.

In this paper, a novel broadband flexible metamaterial absorber is proposed. The unit cell of the absorber is consisted of loaded high-impedance surfaces (HIS) on a flexible polyethylene terephthalate (PET) substrate and a metallic ground plane seperated by a dielectric layer. Losses in the high-impedance surface are introduced by printing the periodic pattern through resistive inks and hence avoiding the typical soldering of lumped resistors. The proposed absorber can obtain the bandwidth with the reflectivity below −10dB in the frequency range of 7.9–18.74GHz.

A reconfigurable metamaterial analog electromagnettically induced transparency like (EIT-like) effect is theoretically and numerically demonstrated in this paper. The unit cell is composed of a stimulated circular loop element and an unstimulated arc slot element, which are both constructed by semiconductor. The proposed designs can realize a continuously tunable EIT-like effect in a broad frequency range, while the number of EIT-like transmission windows can be configured by increasing the number of arc slots.

We designed an omnidirectional reflector for both the transverse electric (TE) and the transverse magnetic (TM) modes in one dimensional liquid-crystal-based heterostructure composed of the ThueMorse multilayered structure and periodic medium. The electrical tunabilities of the reflector are theoretically studied by the Berreman's matrix method. The omnidirectional reflective bands (ORB) of the TE and TM modes have different behaviours. For the TE mode, the ORB is electric independent, and is wider than its counterpart of the TM mode. The ORB of the TM mode becomes narrow with the increase of the incident angle. The polarity-independent ORB was observed in the proposed structure.

In a recent article, Khuyen et al. [J. Appl. Phys. 117, 243105 (2015)] proposed a metamaterial perfect absorber (MPA) with a self-asymmetric structure and claimed that it could produce dual-band “perfect absorption.” In this report, we demonstrate that the self-asymmetric structure is not a true MPA. The cross-polarization reflection, which is induced by coupling between the induced magnetic field and the incident electric field, is ignored in calculation of absorptivity of that structure. The real absorption rate of this structure is below 60%, which indicates that the structure cannot be called a perfect absorber.

Interference induced electromagnetic induced transparency (EIT)-like effect has demonstrated the ability to realize narrow transmission resonances within the single-resonator stop band. Due to the limited plasma density in actual devices, only few reports discuss the plasma metamaterials and truncated photonic crystals which support electromagnetically induced transparency. However, solid state plasma realized by some semiconductors have the advantages of higher order plasma density and the characteristics of the reconfiguration and tunability. Here, we conduct a numerical study of the perfect microwave tunneling in heterostructures composed of solid state plasma metamaterials and truncated photonic crystal. There is particular emphasis on the tunability of tunneling frequency by changing plasma frequency in solid state plasma, as well as the electric energy density distributions in heterostructures. It was found that, compared to conventional metal photonic crystal, the reflectance of tunneling mode can be reduced from −25.8 dB to −41.7 dB with an optimized Q-factor. Further study on electric energy density distribution confirms that EM wave in-plane localization originated from the EIT-like solid state plasma, which gives rise to the three-dimensional enhancement of sub-wavelength EM wave localization, is stronger than EM wave confinement along the propagation direction. Owing to the tunability of plasma, the tunneling frequency channel can be adjusted or reconfigured in a certain range without adjusting the geometry of the heterostructure. It suggests the fabrication for highly sensitive dielectric sensing, optical switches, and so on.

In this paper, the properties of acceptor mode in two-dimensional plasma photonic crystals (2D PPCs) composed of the homogeneous and isotropic dielectric cylinders inserted into nonmagnetized plasma background with square lattices under transverse-magnetic wave are theoretically investigated by a modified finite-difference frequency-domain (FDFD) method with supercell technique, whose symmetry of every supercell is broken by removing a central rod. A new FDFD method is developed to calculate the band structures of such PPCs. The novel FDFD method adopts a general function to describe the distribution of dielectric in the present PPCs, which can easily transform the complicated nonlinear eigenvalue equation to the simple linear equation. The details of convergence and effectiveness of proposed FDFD method are analyzed using a numerical example. The simulated results demonstrate that the enough accuracy of the proposed FDFD method can be observed compared to the plane wave expansion method, and the good convergence can also be obtained if the number of meshed grids is large enough. As a comparison, two different configurations of photonic crystals (PCs) but with similar defect are theoretically investigated. Compared to the conventional dielectric-air PCs, not only the acceptor mode has a higher frequency but also an additional photonic bandgap (PBG) can be found in the low frequency region. The calculated results also show that PBGs of proposed PPCs can be enlarged as the point defect is introduced. The influences of the parameters for present PPCs on the properties of acceptor mode are also discussed in detail. Numerical simulations reveal that the acceptor mode in the present PPCs can be easily tuned by changing those parameters. Those results can hold promise for designing the tunable applications in the signal process or time delay devices based on the present PPCs.

In this paper, a low-loss and high transmission analogy of electromagnetically induced transparency based on electric toroidal dipolar response is numerically and experimentally demonstrated. It is obtained by the excitation of the low-loss electric toroidal dipolar response, which confines the magnetic field inside a dielectric substrate with toroidal geometry. The metamaterial electromagnetically induced transparency (EIT) structure is composed of the cut wire and asymmetric split-ring resonators. The transmission level is as high as 0.88, and the radiation loss is greatly suppressed, which can be proved by the surface currents distributions, the magnetic field distributions, and the imaginary parts of the effective permeability and permittivity. It offers an effective way to produce low-loss and high transmission metamaterial EIT.

In this paper, the properties of complete photonic band gaps (CPBGs) and tunable self-collimation in two-dimensional plasma photonic crystals (2D PPCs) with a new structure in square lattices, whose dielectric fillers (GaAs) are inserted into homogeneous and nomagnetized plasma background are theoretically investigated by a modified plane wave expansion (PWE) method with a novel technique. The novel PWE method can be utilized to compute the dispersion curves of 2D PPCs with arbitrary-shaped cross section in any lattices. As a comparison, CPBGs of PPCs for four different configurations are numerically calculated. The computed results show that the proposed design has the advantages of achieving the larger CPBGs compared to the other three configurations. The influences of geometric parameters of filled unit cell and plasma frequency on the properties of CPBGs are studied in detail. The calculated results demonstrate that CPBGs of the proposed 2D PPCs can be easily engineered by changing those parameters, and the larger CPBGs also can be obtained by optimization. The self-collimation in such 2D PPCs also is discussed in theory under TM wave. The theoretical simulations reveal that the self-collimation phenomena can be found in the TM bands, and both the frequency range of self-collimation and the equifrequency surface contours can be tuned by the parameters as mentioned above. It means that the frequency range and direction of electromagnetic wave can be manipulated by designing, as it propagates in the proposed PPCs without diffraction. Those results can hold promise for designing the tunable applications based on the proposed PPCs.