# Homework Help: Nd:YAG pulsed laser calculations

1. Feb 6, 2009

### dark_knight3

Hi

I have a power meter that measures a Nd:YAG laser intensity with 20 pulses per second as 200 mW. The pulsewidth is 5 ns and I have information relating to the diameter and wavelength of the beam as 3mm and 216 nm, respectively. I also have an expression the intensity or power of the beam as a function of time i.e. I(t) = C exp(-t/pulsewidth), where C is the peak power density.

I have used the equations of E = Pavg(average power)/PRR(pulse repetition rate) to get the power of each pulse.

For the calculation of the peak power density i.e. the C -term in the function representing intensity as a function of time, I need to find that value of I, which corresponds to a peak power value of the beam during it's pulsing. So for peak power, I think it's Pmax = Pavg/DC(duty cycle). So with this max intensity value, I should be able to obtain the peak power density by substituting into I = Cf(t) but what value do I use for time in the expression and since it's peak power density in W.m-2, I suppose the 3mm diameter of the beam gets factored in somehow ?? Do I also need to use the wavelength of the laser in the calculations ?

Last edited: Feb 6, 2009