In this article, we present an efficient phaseless inverse source method (PISM) to reconstruct equivalent sources on a printed circuit board (PCB) using magnitude-only single-plane near-field scanning. The equivalent source distribution reconstructed by the conventional source reconstruction method requires accurate near-field magnitude and phase information, but phase measurement is difficult in many cases due to inaccuracy and complexity. In order to describe the inverse problem between phaseless fields and radiation sources, a nonlinear cost function based on surface integral equations is established. The cost function of the PISM is rapidly minimized by an iterative optimization and regularization technique for nonlinear ill-posed systems. The proposed method gives the characterization of PCBs both for diagnostic tasks of radiation sources and the near-field radiation behavior prediction when the phase information is missing. It also shows excellent robustness in tackling with various near-field data and noises. Both numerical examples and laboratory experiments are given to verify the effectiveness of the proposed method.

A finite-difference time-domain (FDTD) method is developed to analyze electromagnetic scattering from threedimensional (3-D) fully anisotropic periodic structures impinged by obliquely incident plane waves. Starting from Maxwell’s curl equations, we employ material transformation matrices to link the update of the electric and magnetic fields in the FDTD method. The problem under consideration is Bloch-Floquet periodic in the horizontal directions but finite in the vertical direction. At the FDTD truncation boundaries in the horizontal directions, the Bloch-Floquet periodic boundary conditions (BPBCs) are applied, while the perfectly matched layer (PML) absorbing boundary condition is implemented for the vertical direction. We design three different anisotropic models in 3-D simulations to validate our method with a commercial software package COMSOL. These examples show the accuracy and efficiency of the FDTD method for analyzing the propagation characteristics, including reflectance, transmittance, absorptance, and complex reflection and transmission coefficients for the fully anisotropic periodic structures.

A system-combined alternating-direction-implicit finite-difference time-domain (SC-ADI-FDTD) is fully presented and well corroborated for 3-D electromagnetic applications. Spatial differential operators of Maxwell's equations can be expressed as two matrices with the different time-steps in original ADI-FDTD method. From this matrix form, the system chart can be drawn by combining with digital signal processing (DSP) techniques. Based on the intuitive process of the original ADI-FDTD method, we can avoid the repeated computation. Due to the limited computer memory, we employ the unsplited-field convolution perfectly matched layer (CPML) to terminate the FDTD computational domain. Compared with HFSS commercial software, conventional FDTD and original ADI-FDTD methods, the proposed SC-ADI-FDTD method can be well demonstrated and further validated by adopting electromagnetic applications, such as microwave circuits and antennas.

In this paper, we rapidly and accurately solve out reflection and transmission coefficients in the multi-layered fully anisotropic media (MFAM) based on the transfer matrix method (TMM) so that we could find out the energy transmission course (ETC) of plane waves which transmit through MFAM in the air background. Beginning with the Maxwell’s equations, MFAM’s Helmholtz equation could be obtained by known transverse-k vectors of plane waves. Via a series of complicated manipulations applied to derivation of Helmholtz equations, we can attain ordinary differential equation of electric fields which merely exists in a certain direction and then compute four different eigen values in different MFAM regions. Under 3D cases, meanwhile, concrete expressions of other fields can be obtained by given electric fields in the fixed direction. The ETC of electromagnetic fields in the tangential continuity is mainly considered in the TMM, and hence the transferring matrix of electromagnetic field between MFAM regions can be constructed to achieve reflection and transmission coefficients. With various plane-wave modes such as transverse electromagnetic (TEM), transverse electric (TE), and transverse magnetic field (TM) modes, respectively, computational results of MFAM models are solved and adopted to compare with those from the commercial software of COMSOL. Finally, to discuss deeply and efficiently achieve color images, we acquire those reflection and transmission coefficients of more complicated fully anisotropic materials under the different transverse-k vectors. Our work can be as an efficient and reliable solver for excavating prospective applications to predict ETC of models with single/multi-layered materials possessing fully anisotropy.

As an emerging anisotropic two-dimensional (2-D) material, few-atomic-layer black phosphorus (BP) has shown some promising potentials for infrared optoelectronics. Engineering and enhancing its light-matter interaction is significant for many advanced photonic devices. In view of this, we aim to achieve extremely high infrared absorption in monolayer BP with/without subwavelength patterning. By optimizing the polarization and angle of the incident light, the dielectric thickness, and the n-type doping concentration, respectively, infrared radiation can be sufficiently coupled to optical absorption of the monolayer BP in a multiscale photonic structure. The anisotropic infrared absorbance ratios of the unpatterned monolayer BP are enhanced up to 98.2% and 96%, respectively, in in equivalent crystal directions. Moreover, monolayer BP with a design of meta-surface and optimized doping can reach near-unity anisotropic infrared absorption under a smaller incident angle. This paper provides a simple and efficient scheme to trap infrared light for developing promising optoelectronic devices based on monolayer BP and potentially other anisotropic 2-D materials.

In this paper, a high-accurate technique with non-uniform grids is introduced into a system-combined alternative-direction-implicit finite-difference time-domain (SC-ADI-FDTD) algorithm, and then successfully used to analyze electromagnetic propagations. To our knowledge, the conventional FDTD with non-uniform grids can be effectively deal with some edges of the three-dimensional cubes and complicated structures of the tiny objects by modulating the local grid scales, which to the extent improves its reliability and accuracy. However, due to existing the finer grids in the local computational region and the inevitable Courant-Friedrichs-Lewy (CFL) limit in the conventional FDTD, the temporal interval must be determined by the minimum fine spatial grid, resulting in much larger temporal sampling density required during the whole computation process. As the advantage of circumventing the repeated variables, the non-uniform SC-ADI-FDTD (NUSC-ADI-FDTD) cannot only break through the CFL limit to implement the high-efficient computation, but also further save more CPU time in the local microstructure cases. Furthermore, the empirical formula between the spatial sampling density and the CFL factors can be obtained from the numerical fitting method after errors analysis. The numerical simulations of the electromagnetic scattering have been executed to illustrate feasibility and validity of our proposed method.