Yu-Jie Liu

Research on the transmission coefficient of plasma photonic crystals based on the ICCG–SFDTD method

Compared with the traditional finite-difference time-domain (FDTD) method, the symplectic finite-difference time-domain (SFDTD) method has the characteristics of high precision and low dispersion. However, because the higher-order difference is necessary for the calculation, a large sparse matrix is generated. It causes that the computational time is relatively long and the memory is more. To solve this problem, the incomplete Cholesky conjugate gradient (ICCG) method for solving the large sparse matrix needs to be taken into the SFDTD differential equations. The ICCG method can accelerate the iterations of the numerical calculation and reduce the memory with fast and stable convergence speed. The new ICCG–SFDTD method, which has both the advantages of the ICCG method and SFDTD method, is proposed. In this paper, the ICCG–SFDTD method is used for research on the characteristic parameters of the plasma photonic crystals (PPCs) under different conditions, such as the reflection electric field and the transmission coefficient, to verify the feasibility and accuracy of this method. The results prove that the ICCG–SFDTD method is accurate and has some advantages.

Effect of Graphene on the Sunlight Absorption Rate of Silicon Thin Film Solar Cells

The electromagnetic property of graphene is studied by finite-difference time-domain (FDTD) method. As the graphene has excellent electrical conductivity and high transparency, it has certain advantages as a transparent electrode for solar cells. This paper designs a three-layer film structure composed of graphene, silicon, and silicon dioxide (SiO2). Then, the effects of the chemical potential and the scattering rate of the graphene on the light absorption of the film are studied. The study found that the electromagnetic property of graphene is relatively stable, which is not easily influenced by the external environment. After changing its chemical potential, scattering rate, and other parameters, it is found that the film absorption rate is less affected unless the large range of chemical potential changes; it will lead to a decline in the absorption rate of light.

A Research of Nonreciprocal Transmission of Graphene Defect

In this paper, modified transmission matrix method is used to construct one-dimensional multilayer composite membrane structure doped with graphene defect. The optimal construction can be found to realize reciprocity transmission by comparing the influence of the time inversion-symmetry and space inversion-symmetry doped on nonreciprocal transmission. The simulation results show that it cannot ensure the nonreciprocal transmission with rotatory material only. Nonreciprocal transmission should be designed through the structure damage of the space inversion-symmetry to realize it. The structure absorption peak position will move to the direction of the wavelength increase along with the increase of thickness of rotation media. The structure shows the approximate perfect absorption characteristics.

An improved cascaded SO-FDTD method for high temperature magnetized plasma

Abstract An improved cascaded shift operator finite-difference time-domain method is put forward for high temperature magnetized plasma. The calculation formulas of iterative coefficients of this method are given. These results show that the improved method can let the mathematical formula reduce math order and the computational complexity. This is contributed to the derivation of the formula and the compilation of the calculation program. The absorption and reflection characteristics of high temperature magnetized plasma on electromagnetic wave are studied by using this improved CSO-FDTD method. The effects of external magnetic field and temperature on the attenuation coefficient and absorption coefficient of the plasma are discussed. A new phenomenon is found, namely, a sharp transmission peak emerged in the physics band formed by a terahertz wave passing through the monolayer plasma. By studying the effects of external magnetic field and temperature, the phenomenon can be simply produced by monolayer high temperature plasma.

A Study on Plasma Photonic Crystals: Electromagnetic Characteristics Using ICCG-based JEC-CN-FDTD Algorithm

Abstract We extended the current density convolution finite-difference time-domain (JEC-FDTD) method to plasma photonic crystals using the Crank–Nicolson difference scheme and derived the one-dimensional JEC-Crank–Nicolson (CN)-FDTD iterative equation of plasma photonic crystals. The method eliminated the Courant–Friedrich–Levy (CFL) stability constraint and became completely unconditional stable form. The incomplete Cholesky conjugate gradient (ICCG) algorithm is proposed to solve the equation with a large sparse matrix in the CN-FDTD method as the ICCG method improves the speed of convergence, enhances stability, and reduces memory consumption. The JEC-CN-FDTD method is applied to study the characteristics of time domain and frequency domain in the plasma photonic crystal objects. The high accuracy and efficiency of the JEC-CN-FDTD method are confirmed by computing the characteristic parameters of plasma photonic crystals under different conditions such as the electric field distribution of electromagnetic wave, reflection coefficients, and transmission coefficients. Simulation study showed that the algorithm performed stably and could reduce memory consumption and facilitate computer programming.

Study on the transmission properties of periodical and quasi-periodical phononic crystal in elastic wave

The propagation of the elastic wave in phononic crystal is different from the normal uniformity medium. The finite-difference time-domain (FDTD) method is irrelevant to structure model and used widely. Moreover, when the numerical stability of FDTD iterations is satisfied, the elastic waves’ transmission property through periodical and quasi-periodical phononic crystal can be achieved. In this paper, the transmission coefficients of elastic wave through two systems are numerically calculated and the results of band gaps are analyzed. The results are helpful to study phononic crystal.