IEVref:731-03-30ID:
Language:enStatus: Standard
Term: group index
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Symbol: N
Definition: the speed of light in vacuum, divided by the magnitude of the group velocity of the mode

NOTE 1 – For a plane wave of wavelength λ, it is related thus to the refractive index n:

N=nλ dn dλ MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiaad6eacqGH9aqpcaWGUbGaeyOeI0Iaeq4UdW2aaSaaaeaacaqGKbGaamOBaaqaaiaabsgacqaH7oaBaaaaaa@3F3F@

where λ is the wavelength.

NOTE 2 – Each mode has its own group index.


Publication date:1991-10
Source
Replaces:
Internal notes:2016-03-07: Editorial changes: "velocity of light in vacuum" replaced by "speed of light in vacuum". See correspondence "Questions re part 731" 2015-02 and 2015-03. JGO

2017-06-02: Cleanup - Remove Attached Image 731-03-30.gif
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