“…Perpendicular to the beam axis the intensity profile of the laser's output corresponds in good approximation to a Gaussian beam profile: Intensity is the average rate of electromagnetic energy transfered per unit area, where the area is measured on the plane perpendicular to the propagation direction. It is the directional energy flux density of an electromagnetic field, or the magnitude of the Poynting vector S(t) = E(t) × H(t) [Zin09], where E and H is the complex electric and magnetic field, respectively. Using that the magnitude of the magnetic flux |B| = µ 0 |H| and the magnitude of the electric field |E| = c|B|, with c the speed of light, µ 0 the vacuum permeability and 0 the vacuum permittivity, the intensity is given by…”