text: #Non-diffracting Bessel beam.
  
  from LightPipes import *
  import matplotlib.pyplot as plt
  
  Pi=3.1415
  deg=Pi/180.0
  
  wavelength=632.8*nm
  size=5.0*mm
  N=500
  phi=179.8*deg
  n1=1.5
  z=80*cm
  
  F=Begin(size,wavelength,N)
  F=Axicon(phi,n1,0,0,F)
  F=Forvard(z,F)
  I=Intensity(2,F)
  
  plt.imshow(I)
  plt.show()
  