ABCD matrix for reflection and refraction of Gaussian beams at the surface of a parabola of revolution

We report the formulation of an ABCD matrix for reflection and refraction of Gaussian light beams at the surface of a parabola of revolution that separate media of different refractive indices based on optical phase matching. The equations for the spot sizes and wave-front radii of the beams are also obtained by using the ABCD matrix. With these matrices, we can more conveniently design and evaluate some special optical systems, including these kinds of elements. (c) 2005 Optical Society of America

Application of fast Pade approximation in simulating photonic crystal nanocavities by FDTD technology

The exact calculation of mode quality factor Q is a key problem in the design of high-Q photonic crystal nanocavity. On the basis of further investigation on conventional Pade approximation, FDM and DFT, Pade approximation with Baker's algorithm is enhanced through introducing multiple frequency search and parabola interpolation. Though Pade approximation is a nonlinear signal processing method and only short time sequence is needed, we find the different length of sequence requirements for 2D and 3D FDTD, which is very important to obtain convergent and accurate results. By using the modified Pade approximation method and 3D FDTD, the 2D slab photonic crystal nanocavity is analyzed and high-Q multimode can be solved quickly instead of large range high-resolution scanning. Monitor position has also been investigated. These results are very helpful to the design of photonic crystal nanocavity devices. (C) 2008 Elsevier B.V. All rights reserved.

无压灌溉土壤湿润体特征值变化规律与经验解

无压灌溉土壤湿润体形状为球冠,径向和垂向最大湿润距离相等且与时间存在显著的幂函数关系,随着时间的延长,径向和垂向最大湿润距离趋于一定值。湿润体大小与供水压力之间呈抛物线关系,在零压力附近湿润体体积最大。湿润体半径与累计入渗量呈幂函数关系,拟合方程中的系数和指数为一定值,与入渗时间和供水压力无关,在试验条件下,分别为18.467和0.5037。综合以上结果,提出了预测无压灌溉土壤湿润体特征值的经验解模型。