Acta Photonica Sinica ›› 1999, Vol. 28 ›› Issue (12): 1075-1079,1090.

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DISPERSION,GROUP VELOCITY AND GROUP REFRACTIVE INDEX

Li Hui1,2, Xie Shusen1, Lu Zukang2   

  1. 1. Institute of Laser, Fujian Normal University, Fuzhou 350007, China;
    2. National Key Lab of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
  • Received:1999-08-02 Online:1999-12-25 Published:1999-12-25

Abstract: 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.

Key words: Dispersion, Group velocity, Refractive index, Group refractive index

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