色散、群速与群折射率

本文讨论了群折射率存在的物理意义,指出群折射率不仅包含了折射率概念而且还体现了折射率的色散性质,同样能作为材料本身的光学性质参量.接着指出在折射率的白光干涉法测量中存在着忽视色散作用而导致的将群折射率误认为折射率的情况.将群折射率与折射率区别开来,不仅可以消除折射率测量中所存在的错误,而且可以突出色散现象在光传播时间特性上的意义.为此建立了折射率与群折射率的相互变换关系,通过对于典型物质的折射率与群折射率变换关系的计算,说明二者在数值上的差别甚至对于气体介质来说也是不能忽略的.

DISPERSION,GROUP VELOCITY AND GROUP REFRACTIVE INDEX

In this paper,it is pointed out that the significance of dispersion in often neglected in the measurement of refractive index by interference Emphasis is placed on an additional concept of group refractive index which is defined as the ratio of the velocity of light in vacuum to group velocity in medium Intensive analyses show that the physical meanings of group refractive index include both refractive index and its dispersive property Therefore,it is easy to learn why many results of group refractive indices by interferential method are mistaken to be real refractive indices To differentiate refractive index from group one is not only to correct errors in refractive index measurement but also to highlight the temporal characteristic of dispersion phenomenon in the light transport in medium To this end,a transforming relation between the group refractive index and the refractive index is presented and discussed in detail Some examples of typical solid,liquid and gas are also given