How do I create a source field of light through a circular aperture?

I have been trying to construct a code where I propagate a light source through a circular aperture. So far I have

L1=0.5;                     % side length 
M=500;                      % number of samples 
dx1=L1/M;                   % src sample interval 
x1=-L1/2:dx1:L1/2-dx1;      % src coords 
y1=x1; 
lambda=500*10^-9;           % wavelength 
k=2*pi/lambda;              % wavenumber  
w=0.05;                     % source half width (m) 
z=500;                      % propagation dist and focal length (m) 

[X1,Y1]=meshgrid(x1,x1); 
u1=circ(sqrt(X1^2+Y1^2)/w); % src field 
I1=abs(u1.^2);              % src intensity
  
figure; 
imagesc(x1,y1,I1); 
axis square; axis xy; 
colormap('gray'); xlabel('x (m)'); ylabel('y (m)'); 
title('z= 0 m');

but the intensity plot shown does not represent a circular source. Is my definition of u1 incorrect or have a made an error in the coding?

I have defined the function circ as

function[out]=circ(r)
% 
% circle function 
% 
% evaluates circ(r) 
% note: returns odd number of samples for diameter 
% 
out=abs(r)<=1; 
end 

Answer 1

[darova]

First of all you forgout about element-wise:

X1.^2 + Y.^2        % each element of matrix in power '2'

Here is what i tried