In this letter, surface plasmon resonance sensors based on grapefruit-type photonic crystal fiber (PCF)with different silver nano-filling structure have been analyzed and compared though the finite element method (FEM). The regularity of the resonant wavelength changing with refractive index of the sample has been numerically simulated. The surface plasmon resonance (SPR) sensing properties have been numerically simulated in both areas of resonant wavelength and intensity detection. Numerical results show that excellent sensor resolution of 4.17×10-5RIU can be achieved as the radius of the filling silver nanowires is 150 nm by spectrum detection method. Comprehensive comparison indicates that the 150 nm silver wire filling structure is suitable for spectrum detection and 30 nm silver film coating structure is suitable for the amplitude detection.
In this letter, surface plasmon resonance sensors based on grapefruit-type photonic crystal fiber with different silver nano-film structure have been analyzed and compared though the finite element method (FEM). Numerical results show that excellent sensor resolution of 7.143×10-5RIU can be achieved as the thickness of the filling silver film is 30nm by spectrum detection method.
In this study, LD end-pumped Nd:YAG/LBO solid state blue laser is realized by even hollow cavity. A thermal distribution model of Nd:YAG crystal is established. Based on the calculation, the temperature distribution of laser
crystal is obtained. The results show that the temperature decreases from the pump end to the launch end exponentially. When the pumping power is 10 W and the radius of pumping beams is 240μm, a biggest output power 1.06 W of blue light is achieved, giving an optical conversion efficiency of 10.6%.
In this paper, in order to improve the photocatalytic application of TiO2, the low-density material such as Ps and TiCl4 is proposed to be the raw carrier, and the nana-structured TiO2 composite is obtained by combining the sol-gel technology and layer-by-layer self-assembly methods; The pure rutile nano-structured TiO2 whose diameter is about 0.25mm are prepared under different conditions at low temperature. By being calcined under 450 ℃ the hollow sphere TiO2 is prepared and its composition, size, structure analysis and characterization are studied by using X ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermal gravimetric analysis (DSC-TG) respectively.
Multicore fiber lasers have larger mode areas, resulting in higher power thresholds for nonlinear processes such as
stimulated Raman scattering and stimulated Brillouin scattering. Because of longer distributed distance of the cores,
thermal mechanical effects are decreased compared with those of single-core lasers. Therefore, multicore fiber lasers are
proposed as a candidate for the power scaling. The progress of multicore fiber lasers is simply introduced. Optical fields
propagating in multicore fibers are coupled evanescently, resulting in what are called supermodes. In this article, the
coupled-mode theory for analyzing supermode of fiber transmission is introduced. By mean of the theory, assuming
under weak-coupling conditions, the supermodes are approximated as linear superposition of modes of individual cores
with appropriate coefficients. The near-field mode distributions of some supermodes are numerically calculated, and the
corresponding mode distribution patterns are drawn. For making the multicore fiber laser preferentially operate in a
particular supermode so that improving beam quality, an in-phase locking method based on self-imaging Talbot external
cavity is introduced.
In this paper, we report on the near-field distribution of multi-core photonic crystal fiber lasers. The supermodes of
photonic crystal fibers with foursquarely and circularly distributed multi-cores are observed. The supermode properties
are investigated by using full-vector finite-element method (FEM). The mode operations of our 16-core foursquare-array
and 18-core circular-array photonic crystal fiber lasers are simulated by the COMSOL Multiphysics software. The
near-field distribution patterns of in-phase supermode are presented.
The temperature distribution in different cooling system was studied. A thermal distribution model of laser crystal was
established. Based on the calculation, the temperature distribution and deformation of ND:YVO4 crystal in different
cooling system were obtained. When the pumping power is 2 W and the radius of pumping beams is 320μm, the
temperature distribution and end face distortion of the laser crystal are lowest by using side directly hydrocooling
method. The study shows that, the side directly hydrocooling method is a more efficient method to control the crystal
temperature distribution and reduce the thermal effect.
Fronts are elementary structures that separating domains of different steady states in reaction diffusion systems. The local dynamics of front structures have been investigated by a
non-gradient reaction diffusion model of the FitzHugh-Nagumo type. It is found that stable and stationary fronts can be extracted under certain conditions. Based on the local dynamics of front structures, a novel method of image edge detection has been proposed in this paper when fronts are considered as edges of images.
The formation mechanism of stripe patterns in the skin of tropical fishes has been investigated by a coupled two variable reaction diffusion model. Two types of spatial inhomogeneities have been introduced into a homogenous system. Several Turing modes pumped by the Turing instability give rise to a simple stripe pattern. It is found that the Turing mechanism can only determine the wavelength of stripe pattern. The orientation of stripe pattern is determined by the spatial inhomogeneity. Our numerical results suggest that it may be the most possible mechanism for the forming process of
fish skin patterns.
Based on Possion equation, a thermal conduct model of laser crystal was established. The temperature distribution in
laser crystal were obtained,and the optics path difference(OPD) induced by end-face distortion and total OPD were
caculated. Based on the calculation, the focal length of laser crystal with different pumping powers was obtained. The
experimental result agrees with the caculated result very well. When the pumping power is 2 W and the radius of
pumping beams is 320μm; the OPD induced by end-face distortion is 36% of the toatal OPD for ND:YVO4 crystal.
When the pumping power is 5W, the focal length of crystal is 29.7mm. The study shows that, for the solid-stste laser
with high power, the OPD induced by end-face distortion has a large influence on theraml effect of laser crystal. This
study provides a theoretical direction for improving the stability of laser and studying the thermal effect of laser crystal.
Image smoothing and super-resolution are realized by using a reaction diffusion model which is a typical partial
differential equation. The new method is based on the theory of self-organization. In the Turing instability at the bistable
region diffusion process in space leads to the availability of image smoothing and decides the smoothing effects. After
comparing with average filter and median filter it is found that the effects of image smoothing by the reaction diffusion
model are better than that by other filters. Super-resolution can also be achieved by the reaction diffusion model in a
suitable region of control parameters.
In this paper, a new algorithm is proposed for edge detection. A nonliear reaction diffusion equation is employed to
extract the image edges. The mechanism of the new algorithm is based on the local dynamics of the reaction diffusion
system. Three characteristics of dynamics including excitable, Turing/Hopf instability, and bistable dyanmics can be
obtained depending on the control parameters. In the bistable region the system has the ability to detect the edges of
images exactlly. Some of the best results are attained from a number of standard test problems. Compared with the
conventional methods, the new algorithm indicates a higher accuracy and continuity for the image. Moreover, the edge
detection process is not sensitive to the noise.