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???)
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???)