Do you know the dimensions of the laser beam? If x is the dimension of the beam in the direction parallel to the scanning direction of the laser then the residence time of the beam on a spot is 2mm/sec divided by x. Knowing the peak power of 12.8 kW, multiply 12.8 by the residence time to give you Jules of energy which can be divided further by the beam area to get J/cm^2 type of fluence information.

It depends.

First thing first, how long was the total ON time of the laser? This information is critical for Fluence (J/cm2) estimation.

If the laser beam is dwelling on the same location being irradiated, the total Fluence, H(J/cm2) = Laser Power (W)/Beam Size (in cm2) X Pulse Duration (sec) X Total # of Pulses during ON time, where Total # of Pulses = Pulse Frequency (Hz) X ON time (sec)

If the laser beam is being scanned across a surface area, the AVERAGE Fluence over the area is, H(av)(J/cm2) = Laser Power (W)/Scanned Area (in cm2) X Pulse Duration (sec) X Total # of Pulses during ON time, where the Scanned Area (cm2) is approximately ~ Beam Diameter (cm) X Scanned Speed (cm/sec) X Laser ON time (sec). The Scanned Area here is again an approximation as a more accurate estimation would involve the convolution of the laser beam profile over the scanned surface over time. Alternatively, the Scanned Area can be an approximation of the total surface over which the laser beam was traversing (say 2 cm X 2 cm) for whatever predetermined laser ON time.

With given 1.5 ns pulse duration and 2 mm/s beam speed you get 3 pm displacement. It's negligible even for best possible focused UV beam or near-field tip opening, the last might be 30 nm. So, just divide the energy by the spot area.

Correction: In may answer above it should read "then the residence time of the beam on a spot is x divided by 2mm/sec," not the other way around

I have a laser with mean power of 2 Watts and 300um fiber. Using this for 60 sec. irradiation period, how do you calculate the power density (W/cm2) and then the fluency (j/cm2)?

Power density= Laser Power(W)/Beam spot area(cm^2)

Fluence= Power density × Irradiation period (Watt.sec/cm^2) or J/cm^2

How to calculate the laser power density and laser energy density?

I have laser of 650 nm wavelength, power 50 mW , daimeter of beam 16 mm

Irradiation period 30 mint