Picosecond air breakdown studies at 0.53 μm

The laser induced breakdown thresholds of laboratory air at 0.53 μm were measured for pulses varying from 30 to 140 ps for a variety of focal spot sizes. The breakdown threshold fields were found to be proportional to 1/(tp)1/2, where tp is the laser pulse width. Comparison with an earlier work at 1.06 μm under similar conditions indicates that the breakdown thresholds are higher at 0.53 than at 1.06 μm. However, this increase falls short of the λ−2 dependence exhibited by cascade ionization.