Han Li-Hong

Electronic Structure and Optical Properties of Antimony-Doped SnO2 from First-Principle Study

A first-principles study has been performed to calculate the electronic and optical properties of the SbxSn1−xO system. The simulations are based upon the method of generalized gradient approximations with the Perdew—Burke—Ernzerhof form in the framework of density functional theory. The supercell structure shows a trend from expanding to shrinking with the increasing Sb concentration. The increasing Sb concentration induces the band gap narrowing. Optical transition has shifted to the low energy range with increasing Sb concentration. Other important optical constants such as the dielectric function, reflectivity, refractive index, and electron energy loss function for Sb-doped SnO2 are discussed. The optical absorption edge of SnO2 doped with Sb also shows a redshift.

Novel Propagation Properties of Total Internal Reflection Photonic Crystal Fibres with Rhombic Air Holes

We investigate the propagation properties of a multi-layer photonic crystal fiber with novel rhombic air holes using the finite element method, and calculate the dependence of the propagation properties on the wavelength in the fiber with different geometrical structural parameters, including the internal angle and the external arrangement of the rhombic air holes. Optimizing these parameters, we design a photonic crystal which exhibits both a small dispersion value and low loss near the wavelength of 1.55μm.

Electronic structures of stacked layers quantum dots: influence of the non-perfect alignment and the applied electric field

Electronic structures of the artificial molecule comprising two truncated pyramidal quantum dots vertically coupled and embedded in the matrix are theoretically analysed via the finite element method. When the quantum dots are completely aligned, the electron energy levels decrease with the horizontally applied electric field. However, energy levels may have the maxima at non-zero electric field if the dots are staggered by a distance of several nanometers in the same direction of the electric field. In addition to shifting the energy levels, the electric field can also manipulate the electron wavefunctions confined in the quantum dots, in company with the non-perfect alignment.

Lateral stress-induced propagation characteristics in photonic crystal fibres

Using the finite element method, this paper investigates lateral stress-induced propagation characteristics in a photonic crystal fibre of hexagonal symmetry. The results of simulation show the strong stress dependence of effective index of the fundamental guided mode, phase modal birefringence and confinement loss. It also finds that the contribution of the geometrical effect that is related only to deformation of the photonic crystal fibre and the stress-related contribution to phase modal birefringence and confinement loss are entirely different. Furthermore, polarization-dependent stress sensitivity of confinement loss is proposed in this paper.

Influence of disorder and deformation on the optical properties of a two-dimensional photonic crystal waveguide

We investigate the effect of disorder and mechanical deformation on a two-dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied using the finite element method. Results show that the geometric change of the dielectric material perpendicular to the light propagation direction has a larger influence on the waveguide characteristics than that parallel to the light propagation direction. Mechanical deformation has an obvious influence on the performance of the waveguide. In particular, longitudinal deformed structure exhibits distinct optical characteristics from the ideal one. Studies on this work will provide useful guideline to the fabrication and practical applications based on photonic crystal waveguides.