Stoichiometric changes to KH 2 PO 4 during laser-induced breakdown

Raluca A. Negres, Sergei O. Kucheyev, Paul P. DeMange, Christopher W. Carr, Stavros G. Demos, Gregory J. Exarhos, Arthur H. Guenther, Norbert Kaiser, Keith L. Lewis, M. J. Soileau, Christopher J. Stolz
2005 Laser-Induced Damage in Optical Materials: 2004  
The local structure of KH 2 PO 4 crystals (so-called KDP) at laser-induced damage sites created by irradiation with ∼ 3-ns, 355-nm laser pulses is studied by a combination of Raman scattering and photoluminescence spectroscopies. We compare spectra from pristine material, surface and bulk laser-induced damage sites, as well as from KPO 3 references. Results show that irradiation with fluences above the laser-induced breakdown threshold leads to stoichiometric changes at surface damage sites but
more » ... not at bulk damage sites. New spectroscopic features are attributed to dehydration products. For the laser irradiation conditions used in this study, the decomposed near-surface layer absorbs photons at ∼ 3.4 eV (364 nm). These results may help explain the recently reported observation that surface laser damage sites in KDP crystals tend to grow with subsequent exposure to high-power laser pulses, while bulk damage sites do not.
doi:10.1117/12.584943 fatcat:2hfncqf3tfa3xkue6n25prc7dq