Dear all :
I feel a little confused in simulation of nonlinearity in MEEP .
In general , for the intensity of spectral is proportional to |E|^2
and the nonlinearity (EX :chi3) is proportional to |E|^8 .
For this case , if I change the amplitude into 2 times of the
original number of the electric field of the example( 3rd-harm-1d.ctl ) ,
then I would get the number of 3rd frequency is proportional to |2*E|^8
= proportional to |E|^64 .
But I get a problem of this concept, I don’t get the number which is
proportional
to |E|^64 in simulation results .
I don’t know what’s wrong with the nonlinearity in MEEP .
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(define-param sz 100) ; size of cell in z direction
(define-param fcen (/ 1 3)) ; center frequency of source
(define-param df (/ fcen 20)) ; frequency width of source
(define-param amp 1.0) ; amplitude of source
(define-param k 1e-2) ; Kerr susceptibility
(define-param dpml 1.0) ; PML layer thickness
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Results :
Amp = 1 ; intensity of the 1st frequency : 0.510 ;
intensity of the 3rd frequency : 0.0017 ;
Amp = 2; intensity of the 1st frequency : 2.02 ;
intensity of the 3rd frequency : 0.0237 ;
For the fundamental frequency(1st ) is proportional to |E|^2 , that is 4
times larger than the original number .
But for the third harmonic frequency(3rd ) is not proportional to
|2*E|^8 = proportional
to |E|^64
Thanks
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