高斯型扩散光波导导模特性的研究

本文应用最陡下降逼近理论(SDAT),研究了高斯型渐变折射率分布扩散光波导的导模特性。以二项式折射率分布光波导作为参考系,直接以高斯项作为微扰,避免了普通微扰方法的发散困难及其在近截止区的反常,导出了导模传播常数与模场分布的解析表达式。

STUDY OF GUIDED MODES IN GAUSSIAN DIFFUSED OPTICAL WAVEGUIDE WITH THE STEEPEST DESCENT APPROXIMATION THEORY

In calculating the propagation constants and field distribution of modes indiffused optical waveguide with Gaussian refractive index profile,a generally ac-cepted approach is to consider the Gaussian profile simplified as a quadric anhar-monic oscillator,this leads to a divergent Rayleigh Schrodinger perturbation expan-sion and exists great difficulty in solving the problem using ordinary perturbationmethod.Furthermore,even if the divergent difficult is overcome with renormalizedtechnique,the calculation results are not credible near cut-off region if that sim-plification of gaussian distribution is used due to the influence of high order anha-rmonic term.In this paper,we have used the steepest descent approximation theoryto solve this problem.By using Gaussian function as perturbed term directly,wehave gotten over both the divergent difficulty and the influence of unsuitable appr-oximation of Gaussian function near cut-off region and obtained the analyticalexpression for the dispersion curve and field distribution.