Question: @Chris how do you measure the intensity of a laser?

Chris Armstrong answered on 23 Jun 2015:

In terms of Units its done in W/cm^2 which is a tad annoying as its not quite standard units but thats the default for the field. What that means is the power delivered per area, what this relates to physically is the amount of photons we can focus to the single spot and what energy they can deliver.

In terms of practically doing it, we direct the full beam onto a calorimeter which tells us the energy delivered, we know the pulse length of the laser from timing metrics in the system, and the area of the laser pulse (for us the pulse can be thought of as a pancake of light moving through the system rather than a continuous wave). From those pieces of information and a little maths we can determine the intensity of the laser pulse.