function fDC2=propagateField(fDC, vMod, L, n, lambda)
% Propagate optical fields by distance L in a medium with
% the refractive index n.


try 
    n;
catch
    n=1.0;
end
try
    lambda;
catch
    lambda = 1064e-9;
end

c=299792458;
f0=c/lambda;
fList = (f0+vMod)';

s=size(fDC);
if numel(s) < 3
    s(3)=1;
end
f = repmat(fList, [s(1),1,s(3)]);

fDC2 = fDC .* exp(i*2*pi*n*L*f/c);