矢量衍射理论在光盘中的应用

衍射计算是设计光盘光学系统的基础。只读光盘信息符（ 坑点） 尺寸可以和波长相比拟或在更小时标量衍射理论不再适用。本文将光盘信息符抽象成二维光栅，应用耦合波理论导出了当用平面波检测光盘时衍射波场的计算公式，得到了衍射强度 坑深曲线，并提出了临界坑深的概念。分析表明，临界坑深随着信息符横向尺寸的变小而变小，这将导致衍射波光强变化的减小，从而限制了光盘的存储密度。本文还分析了检测平面波的偏振态对衍射波强度的影响

Application of coupled-wave theory in optical disk

Diffraction calculation is the basis of designing optical system of optical disk. Classic scalar diffraction theory can't get correct result when the size of information mark (pit) of read only disk is comparable to or smaller than the wavelength of light. The disk is modeled as a two dimensional grate in this paper, and formulas of diffracted field are derived employing coupled wave theory when the disk is detected by a plane wave. The curve of diffraction intensity versus pit depth is obtained, and the concept of critical depth is put forward. According to the analysis, the critical depth decreases when transverse dimension of the pit reduce, which will result in the decrease of the diffraction intensity variety and limit the storage density of the optical disk finally. The effect of the detecting plane wave's polarization on the diffraction intensity is also investigated in this paper.