Effects of wavelengths combination on initiation and growth of laser-induced surface damage in SiO 2

Campaigns of laser damage tests at 1w of Nd-YAG laser (1064 nm), 3w and with a combination of these two wavelengths, were conducted to complete previous existing data on damage growth in fused silica output surface. It is known that UV light is very effective in inducing preexisting damage craters to grow. When both wavelengths are present, the effect of 1w beam on damage growth depends on the delay between the IR and the UV beam. When the 1w reaches the sample before the 3w, it has nearly no consequence on growth rate. On the opposite, when the IR beam is delayed and strikes the sample after the 3w pulse, its energy simply adds to the UV in enhancing damage growth. Damage initiation is much more affected by 3w than 1w pulses. However, the number of surface damage craters also increased by the addition of 1w photons to the UV beam.