Power Considerations for Q-Switched Pulsed Beams

The actual energy per pulse is an important additional consideration for pulsed beams. Energy is measured in joules, and as discussed above, individual pulses may damage the scanhead, even when the average power falls within the safe region of the operating space chart. For this reason it is necessary to understand the limits in Joules for lasers that use pulsing to increase the delivered energy, most commonly the Q-Switched laser.

This chart shows the damage thresholds for pulsed beam energies for the three wavelength regimes. The lines represent the maximum energies per pulse for various spot sizes that correspond to 5J/cm 2 for the 3 to 100 micron wavelengths, 2.5J/cm2 for the 700nm to 3 micron range, and 250mJ/cm2 for the UV-Visible range from 190nm to 700nm. When operating with pulsed lasers, calculate the energy per pulse to ensure that the values fall below these lines for the wavelength of the laser. Operation above these values will likely cause damage to the scanhead apertures.