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inconsistency between "neff" and "beta"?

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I am using "Mode Analysis" study to find a guided mode in a structure. I can ask Comsol to compute separately the effective index of the mode (neff) and the propagation constant (beta). The relationship between these two must be straightforward:

beta=neff*k=neff*2*pi/lambda

However, if I compare neff and beta as Computed by Comsol, they do not quite follow this relationship. Generally the difference between neff and (beta*lambda/(2pi)) is of the order of 1%.

I wonder why there is this difference and which of the two quantities is computed more accurately by Comsol (if any???)

0 Replies Last Post Jun 26, 2015, 10:27 a.m. EDT
COMSOL Moderator

Hello Andriy Gorbach

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