
506
Laser-Induced Damage in Optical Materials
anirradiance peaking at 30 kW/cm
2
with the uence of ~0.6 mJ/cm
2
from each micro-
pulse [12]. is is depicted clearly in noncontact prolometry scans of the outcoupler
before and aer it was used in the FEL, as shown in Figure 18.4.
In addition to performing prolometry on cavity optics ex situ, the mirrors were
observed in situ with visible and FLIR cameras during operation of the JLab FEL. What
was noted [12] was that occasionally damage would initiate at a relatively low irradiance,
ca. 10 kW/cm
2
as evidenced by a sudden increase in scattered coherent harmonic light
as viewed by the visible camera ...