Shao-Bin Liu

Comment on “Photonic bands in two-dimensional microplasma array. I. Theoretical derivation of band structures of electromagnetic waves” [J. Appl. Phys.101, 073304 (2007)]

Recently, theoretical derivation of band structures of electromagnetic waves in two-dimensional microplasma array has been induced by Osamu Sakai et al. [J. Appl. Phys. 101, 073304 (2007)] using a modified plane wave expansion (PWE) method and a frequency-dependent finite difference time–domain (FDTD) method. This report reveals band diagrams with the effects of plasma electron collision frequency, especially focuses on the TE wave by nonmagnetized plasma. Although the band diagrams of TE wave and formulas of calculation look correct at first glance, there are some mistakes in the report which are unfortunately ignored by the authors. The correct formulas of the modified PWE method and FDTD method will be proposed.

A novel ultrathin and broadband microwave metamaterial absorber

In this paper, the design, simulation, fabrication, and measurement of an ultrathin and broadband microwave metamaterial absorber (MMA) based on a double-layer structure are presented. Compared with the prior work, our structure is simple and polarization insensitive. The broadband MMA presents good absorption above 90% between 8.85  GHz and 14.17 GHz, with a full width at half maximum (FWHM) absorption bandwidth of 6.77 GHz and a relative FWHM absorption bandwidth of 57.3%. Moreover, the structure has a thickness of 1.60 mm (only λ/20 at the lowest frequencies). The experimental results show excellent absorption rates which are in good correspondence with the simulated results. The broadband absorber is promising candidates as absorbing elements in scientific and technical applications because of its broadband absorption and polarization insensitive.

Complete photonic band gaps and tunable self-collimation in the two-dimensional plasma photonic crystals with a new structure

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.

Analyzing the photonic band gaps in two-dimensional plasma photonic crystals with fractal Sierpinski gasket structure based on the Monte Carlo method

In this paper, the properties of photonic band gaps (PBGs) in two types of two-dimensional plasma-dielectric photonic crystals (2D PPCs) under a transverse-magnetic (TM) wave are theoretically investigated by a modified plane wave expansion (PWE) method where Monte Carlo method is introduced. The proposed PWE method can be used to calculate the band structures of 2D PPCs which possess arbitrary-shaped filler and any lattice. The efficiency and convergence of the present method are discussed by a numerical example. The configuration of 2D PPCs is the square lattices with fractal Sierpinski gasket structure whose constituents are homogeneous and isotropic. The type-1 PPCs is filled with the dielectric cylinders in the plasma background, while its complementary structure is called type-2 PPCs, in which plasma cylinders behave as the fillers in the dielectric background. The calculated results reveal that the enough accuracy and good convergence can be obtained, if the number of random sampling points of Mont...

Dispersion Properties of Three-Dimensional Plasma Photonic Crystals in Diamond Lattice Arrangement

Dispersion properties of two types of three-dimensional plasma photonic crystals are theoretically investigated by a modified plane wave expansion method, which is composed of isotropic dielectric and nomagnetized plasma. The eigenvalue equations of two types of structures depend on the diamond lattice realization (dielectric spheres inserted in plasma background or vice versa), are deduced respectively. The band structures can be obtained by solving the nonlinear eigenvalue equations. The influences of relative dielectric constant and plasma frequency with different filling factors on dispersive relation are demonstrated, respectively. The numerical results show that the band structures can be modulated by the parameters for the two types of plasma photonic crystals.

Dual-gated tunable absorption in graphene-based hyperbolic metamaterial

The use of a dual-gated tunable absorber in graphene-based hyperbolic metamaterial (GHMM) in the near-infrared frequency range was investigated. The horizontal and vertical parts for relative permittivity of GHMM, which consists of monolayer graphene and conventional dielectric, were tuned using the chemical potential. To obtain a large absorption, GHMM was placed on top of a stacked structure containing dielectric and graphene layers and a copper reflector was placed at the bottom. The dual-gated absorber had multiband absorption, which was tuned using the chemical potential of graphene and GHMM. This study focuses on the variation of the absorption with change in the chemical potential and dielectric thickness. The results show that multiband absorption could be attained when chemical potential and dielectric thickness was changed. Broadband absorption could be generated when the frequency ranged from 215 THz to 250 THz. This phenomenon may be valuable for a variety of important applications including optical communication technology and near-infrared stealth communication.

Novel three-band microwave metamaterial absorber

In this paper, a novel three-band microwave metamaterial absorber is presented. The proposed absorber consists of a metallic planar cross and square layer on the top and a metallic ground plane at the bottom. They are separated by a dielectric layer. The experimental results show that the proposed absorber exhibits triple band absorption responses lying in C-band, X-band, and Ku-band. The proposed absorber can perform absorption peaks at three resonant frequencies of 6.16, 8.76, and 12.54 GHz with the absorption of 99.87, 99.98, and 99.99% can be acquired, respectively. In addition, the absorber can operate at large incident angles for both TE and TM polarization.

Electromagnetically induced transparency with large group index induced by simultaneously exciting the electric and the magnetic resonance

In this paper, we numerically and experimentally demonstrate classical analogy of electromagnetically induced transparency (EIT) with simultaneously exciting the electric and the magnetic resonance. The cut wire and the split-ring resonator (SRR) are chosen as the bright and the quasi-dark EIT resonators, respectively. Under incident electromagnetic wave illumination, an EIT-like sharp transmission window can be observed. The group index exceeds 140, which can be applied for slow electromagnetic wave velocity. Furthermore, the underlying physics can be interpreted by the concept of hybridization model. The simultaneous excitation of the electric and the magnetic resonance can make up for the shortcomings of the other existing designs. More importantly, it can enrich metamaterial analogy of electromagnetically induced transparency.

Analysis of Voigt effects in dispersive properties for tunable three-dimensional face-centered-cubic magnetized plasma photonic crystals

The Voigt effects in dispersive properties of three-dimensional magnetized plasma photonic crystals (magnetized plasma spheres immersed in dielectric background), composed of homogeneous dielectric and magnetized plasma with face-centered-cubic lattices are theoretically investigated based on the plane wave expansion method, as incidence electromagnetic wave vector is perpendicular to the external magnetic field. The equations for calculating the band diagrams are theoretically deduced. The influences of dielectric constant of dielectric, plasma collision frequency, filling factor, plasma cyclotron frequency, and plasma frequency on the dispersive properties are studied in detail, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that the photonic band gap (PBG) can be manipulated by plasma frequency, filling factor, plasma cyclotron frequency, and the relative dielectric constant of dielectric, respectively. However, the plasma collision frequency has no effects on the location and relative bandwidth of the PBG. The locations of two flatbands regions cannot be tuned by any parameters except for plasma frequency and plasma cyclotron frequency.

Cylindrical optimized nonmagnetic concentrator with minimized scattering

By using optimized transformation function, we research on a minimized scattering nonmagnetic concentrator, which can realize impedance matching at the inner and the outer boundaries. It has been demonstrated that the optimized transformation function method can improve the concentrating performance remarkably. The cylindrical anisotropic shell can be mimicked by radial symmetrical sectors which alternate in composition between two profiles of isotropic dielectrics, and the permittivity in each sector can be properly determined by the effective medium theory. The nonmagnetic concentrator has been validated by full-wave finite element simulations. We can believe that this work will improve the flexibilities for the EM concentrator design.