The maximal output fluence of high-power laser systems remains limited by KH2PO4 (KDP)-based optical components used to convert the infrared pulses to 3ω pulses. The correlation between optical defects (scales of a few micrometers) on KDP crystal surfaces and damage initiation was systematically investigated by combining laser-induced fluorescence (FL) and light-scattering microscopies incorporated an in-situ damage testing facility (wavelength at 355 nm and pulse width of 7 ns). We demonstrated that the surface defects featuring both FL and light-scattering have a high propensity to damage. The scattering feature of the FL precursors was found to be a key factor for damage initiation, whose physical mechanism was thoroughly revealed. The results further implied that the removal of such damage precursors can greatly improve the damage resistance of KDP-based crystals. Considering that this combined imaging technique is noninvasive, the results establish this methodology as an attractive and non-destructive tool for evaluating and improving the surface damage performance of KDP-based crystals used in high-power lasers.
A novel oxyfluoride glass (OFG) was prepared. The laser induced damage threshold (LIDT) of the novel OFG is 24.9%
higher than fused silica under 355nm nanosecond laser irradiation by R-on-1 procedure. Characterization by optical
microscope and scanning electron microscope shows that the initial damage morphologies of two kind of materials are
significantly different. Experiment results indicate that the novel OFG can be a good candidate component material for
high energy laser applications.
A series of fused silica surface have been created by reaction ion etching to determine the effect of the contamination
level on surface state and optical performance of the optics. The results show that both impurity elements contamination
and scratches of fused silica surface can be removed dramatically during RIE process. The laser induced damage
threshold is raised by 37.6% when the polishing layer is removed for a thickness of 6μm, and the laser weak absorption
doesn’t increase obviously. The results can provide technique support for improving laser induced damage performance
of fused silica.
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