INTERFERENCE Demonstration of interference

by Chuck DiMarzio Northeastern University May 2009

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Contents

Set parameters

lambda=10.59e-6;  % Wavelength in meters for co2 laser
c=299792458; % m/s
f=c/lambda;
tstep=1/f/50; % Step for plotting
tmax=20/f;    % Max time to plot
tau=8/f;      % Pulse length
t=(0:tstep:tmax);  % Time axis

Set fields for demonstration

field1=1.5*cos(2*pi*f*t).*(t<tau);  % Reference
%
%
field2inphase=cos(2*pi*f*t).*(t<tau); % Different signal fields
field2neg=-field2inphase;
field2quad=sin(2*pi*f*t).*(t<tau);
field2delay=sin(2*pi*f*t).*(t<2.5*tau).*(1.5*tau<t);

Compute sums

inphase=field1+field2inphase;
quad=field1+field2quad;
neg=field1+field2neg;
delay=field1+field2delay;

Plot

fig1=figure;plot(t*1e15,field2inphase);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('E');
fig3=figure;plot(t*1e15,field2quad);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('E');
fig5=figure;plot(t*1e15,field2neg);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('E');
fig7=figure;plot(t*1e15,field2delay);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('E');

fig2=figure;plot(t*1e15,inphase);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('Sum');
fig4=figure;plot(t*1e15,quad);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('Sum');
fig6=figure;plot(t*1e15,neg);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('Sum');
fig8=figure;plot(t*1e15,delay);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('Sum');

fig9=figure;plot(t*1e15,field1);
axis([0,tmax*1e15,-2.5,2.5]);xlabel('t, time, fs');ylabel('E');