A 1064nm Q-switched laser beam with beam diameter of 3mm, a peak pulse power of 1MW and full beam divergence of 5mrad is focused by a 1cm lens. Find the peak intensity at a distance of 1mm from the focus. Hint: calculate the M² value of the beam and then calculate the Rayleigh range for such a beam at the focus of the lens. Afterwards calculate what the beam diameter would be at a distance from 1mm from the focus. A simpler way is to use geometry since we are given the initial beam diameter, for your own curiosity compare the answer you get to the more precise method.

possible results :50.9 PW/m^{2 ,} 55.1 TW/m^{2 ,} 13.8 TW/m^{2 ,} 12.7 PW/m²