We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedded in the two-dimensional optical lattice gives rise to some unique properties. It is interestingly found that for the negative defect, stable surface defect gap solitons can exist both in the semi-infinite gap and in the first gap. The deeper the negative defect, the narrower the stable region in the semi-infinite gap will be. For a positive defect, the surface defect gap solitons exist only in the semi-infinite gap and the stable region localizes in a low power region.
Electromagnetic cloaking based on the scattering cancellation method have been reviewed. The possibility of designing the tunable electromagnetic cloaking is analytically suggested with a single cloak composed of homogeneous materials,including semiconductor,superconductor,ferrite and ferroelectrics by using Mie scattering theory. The simulated results demonstrate that the cloaks with these homogeneous materials can drastically reduce the total scattering cross sections of the cloaked system by using the finite element method. These cloaking frequencies can be controlled by external field through tuning the permittivity or permeability of these materials by the applied field,such as temperature,magnetic field and electric field. These may provide some potential ways to design tunable cloaking with considerable flexibility.
0.91Pb（Zn1/3Nb2/3）O3-0.09PbTiO 3（PZN-9%PT） single crystals with different orientations are investigated by using a spectroscopic ellipsometer,and the refractive indices and the extinction coefficients are obtained.The Sellmeier dispersion equations for the refractive indices are obtained by the least square fitting,which can be used to calculate the refractive indices in a low absorption wavelength range.Average Sellmeier oscillator parameters E o,位 o,S o,and E d are calculated by fitting with the single-term oscillator equation,which are related directly to the electronic energy band structure.The optical energy bandgaps are obtained from the absorption coefficient spectra.Our results show that the optical properties of [001] and [111] poled crystals are very similar,but quite different from those of the [011] poled crystal.
Convolution kernel-based non-uniform fast Fourier transform （NUFFT） is an effective image reconstruction method for Fourier domain optical coherence tomography. By measuring the reconstruction error, a general method for finding the optimal parameters of the kernel function is investigated. Performances in terms of point spread function and computation time are evaluated. The NUFFT with optimal parameters yields signal sensitivity of over 40 dB, with a computation time that is decreased by 85% compared with the conventional oversampling NUFFT. In vivo images of finger tissue are efficiently reconstructed through the proposed reconstruction method.
