Long‐pulse breakdown with 10.6‐μm laser radiation

We have investigated material initiated air breakdown using a long 10.6‐μm pulse (tens of microseconds) and attributed the breakdown initiation to a thermal mechanism. In particular, breakdown initiated on glass fibers after irradiation times up to 35 μsec with power densities of 106−107 W/cm2 is reported. Measured parameters included breakdown threshold, time to breakdown, plasma expansion dynamics, and transmission of 10.6‐μm radiation through the plasma.