计算脉冲在非线性耦合器中演化的Matlab 程序 }U7><I
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% This Matlab script file solves the coupled nonlinear Schrodinger equations of GvT'v0&+
% soliton in 2 cores coupler. The output pulse evolution plot is shown in Fig.1 of c-^\YSDMN
% Youfa Wang and Wenfeng Wang, “A simple and effective numerical method for nonlinear uCpk1d
% pulse propagation in N-core optical couplers”, IEEE Photonics Technology lett. Vol.16, No.4, pp1077-1079, 2004 Z(-@8=0
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%fid=fopen('e21.dat','w'); 4*9:
N = 128; % Number of Fourier modes (Time domain sampling points) u-E*_%y
M1 =3000; % Total number of space steps b7bbrR8
J =100; % Steps between output of space ws$!-t4<(
T =10; % length of time windows:T*T0 vZpt}u
T0=0.1; % input pulse width 4]]1JL(Ka
MN1=0; % initial value for the space output location "5R8Zl+
dt = T/N; % time step O
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n = [-N/2:1:N/2-1]'; % Index /8w
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t = n.*dt; UGJ#
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u10=1.*sech(1*t); % input to waveguide1 amplitude: power=u10*u10 .pQ4#AJ
u20=u10.*0.0; % input to waveguide 2 &U8W(NxN
u1=u10; u2=u20; -kd_gbnr3
U1 = u1; `$D2w|
U2 = u2; % Compute initial condition; save it in U pV^hZ.
ww = 4*n.*n*pi*pi/T/T; % Square of frequency. Note i^2=-1. S_B;m1
w=2*pi*n./T;
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g=-i*ww./2; % w=2*pi*f*n./N, f=1/dt=N/T,so w=2*pi*n./T Yj^n4G(h
L=4; % length of evoluation to compare with S. Trillo's paper n.$wW
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dz=L/M1; % space step, make sure nonlinear<0.05 9L'R;H?L
for m1 = 1:1:M1 % Start space evolution wA<#E6^vG
u1 = exp(dz*i*(abs(u1).*abs(u1))).*u1; % 1st sSolve nonlinear part of NLS kiFTx
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u2 = exp(dz*i*(abs(u2).*abs(u2))).*u2; 0UvN ws
ca1 = fftshift(fft(u1)); % Take Fourier transform 64OgE!
ca2 = fftshift(fft(u2)); v='h
c2=exp(g.*dz).*(ca2+i*1*ca1.*dz); % approximation e&(Di,%:
c1=exp(g.*dz).*(ca1+i*1*ca2.*dz); % frequency domain phase shift [/ E_v gZ
u2 = ifft(fftshift(c2)); % Return to physical space )5U&^tJ
u1 = ifft(fftshift(c1)); -\!"Kz/
if rem(m1,J) == 0 % Save output every J steps. TY3WP$u
U1 = [U1 u1]; % put solutions in U array Td5;bg6Qy
U2=[U2 u2]; &dkj