Plotting the behavior of a diagonal matrix

I have a diagonal matrix of N th power. Eventhough I plot the variation of matrix element with N, I am not getting the expected plot. Basically I want to find the variation of diagonal matrix with power N when eigen decomposition is performed.

The code is,

clc;
close all;
clear all;

%parameters
c=3*10^8;
lambda_0=1559*10^(-9);
lambda_p=1560.7*10^(-9);
lambda_s=1580*10^(-9);
gamma=0.011;
d_slope=0.03e3;
d_slope1=-0.10e3;
P_p=1;
L=250;

%range
m=1:100;

%equations.
delta_beta=((-2*pi*c)/lambda_0^2)*d_slope*(lambda_p -lambda_0 )*(lambda_p -lambda_s).^2;
k=delta_beta+2*gamma*P_p;
g = ((-delta_beta).*(delta_beta./4+gamma*P_p)).^(1/2); 
for j=1:length(m);
D(j)=(1./(g.^(m(j)))).*(g.*cosh(g.*L)+sinh(g.*L).*(sqrt(gamma*P_p^2-(k./2).^2))).^(m(j));
end
plot(m,D);

[KALYAN ACHARJYA]

Are you refering diagonal elements of D matix? Though D is not a square matrix, how you expression the diagonal elements?

>> whos D
  Name      Size             Bytes  Class     Attributes

  D         1x100              800  double     

What about n, in the code there is no N/n, is it m?

[Csaba]

You have only vectors in your code, there is no matrix. What are you referring to?