Narrow Results

In this paper, three kinds of controllable nonlinear left-handed materials (DNLHMs) are proposed and analyzed, which are designed by introducing inductors and capacitors into the traditional nonlinear left-handed materials (NLHMs) as inhomogeneous doped elements. Due to such changes, several new transmission properties have been presented through finite-difference time-domain (FDTD) simulations. These have brought new features to our DNLHMs. On one hand, the original passband in the traditional nonlinear left-handed material is narrowed after introducing inductors. In addition, a new passband, which does not exist in doped linear LHMs, is generated. On the other hand, through introducing capacitors, the original passband of the nonlinear left-handed material can be shifted, resonance frequency can be changed, and a new passband can be generated. When capacitors and inductors are introduced simultaneously, the material properties, such as the number of passbands, the characteristic resonance frequency, and the bandwidth, can also be changed. Noting these characteristics, the values of the introduced inductors and capacitors are varied to investigate the spectrum changes of DNLHMs. Then, a series of controllable properties of the DNLHMs can be retrieved. And more importantly, the designed DNLHMs give the adjustability of suppressing high harmonics, which is not possible in the past materials.

In this paper, we propose and simulate the surface plasmon polariton nanofocusing process by using Finite-difference Time-domain (FDTD) method. The maximum enhancement factor at the taper end area is optimized with different wavelength of the excitation laser. With the advantage of SNOM, the SPP nanofocusing is experimentally observed by illuminating the tapered CdS nanoribbon deposited on the Ag film. The SPP dispersion is used to predict the optimal taper angles of the structure. As the emission of the focused SPP at the taper end, the proposed plasmonic structure can be severed as a light nanosource emitter in the future optical integrated circuits.

Two-photon absorption and optical limiting of two fluorenyl-based derivatives, 9,9-dimethyl-2,7-bis((E)-4-nitrostyryl)-9H-fluorene and 9,9-dimethyl-2,7-bis((E)-4-((E)-4-nitrostyryl)styryl)-9H-fluorene, in gas phase and solvent with nanosecond laser pulse have been theoretically investigated by solving the coupled rate equations and the field intensity equation employing an iterative predictor–corrector finite-difference time-domain (FDTD) method. The results show that both optical limiting properties and two-photon absorption cross-section strongly depend on the length of these molecules and the solvent. Moreover, the dynamical two-photon absorption behavior is affected by the thickness of samples and the pulse duration. These discoveries demonstrate that these fluorenyl-based derivatives possess highly promising characteristics and have potential applications for optical limiting devices.

In this study, we report photonic band structures and optical transmissions of some SiC polytypes, such as 3C, 2H, 4H, and 6H, and their multilayers, which have the form of a hexagonal photonic crystal at two-dimensional (2D) scale. Through the finite-difference time-domain computational simulations, we found that spatial electric-field variations of electromagnetic waves depend on the radius of dielectric rods of the multilayer crystal structure, and the central structural geometry of 4H- and 6H-SiC hexagonal polytypes was found to cause a remarkable increase of the wave vector $k$ in $x$ and $y$ directions. We also found a correlation between the local central structures of the optical modes in the 2D hexagonal crystal of 4H- and 6H-SiC polytypes. The wave-guiding in 4H- and 6H-SiC polytypes in the central core of the model geometry enabled the integration of defects to achieve a wide spectrum of technological functionalities, such as devices with striking features for miniaturized sensors and quantum information processing.