If we know the center electric amplitude

*E*0 of a Gaussian beam as shown in the equation below. We can calculate the beam power according to the equation shown here.The power can be calculated by integrating the Poynting over a incident surface.

I =<S> = 1/2 (E x H)

I =<S> = 1/2 (E x H)

Then the final power is:

The beam intensity at center of the beam is

So the relation between the power and center beam intensity of a Gaussian beam is: