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DF: Fachverband Dielektrische Festkörper
DF 9: Electric, Electromechanical and Optical Properties I
DF 9.6: Vortrag
Donnerstag, 29. März 2007, 12:00–12:20, H48
Comprehensive study of surface damage induced by SFG in Lithiumtriborate (LBO) — •Stefan Möller, Änne Andresen, Christoph Merschjann, Manfred Neumann, and Mirco Imlau — Department of Physics, University of Osnabrück, D-49069 Osnabrück
We have investigated the build-up of surface damages of LiB3O5 single crystals generated during sum-frequency generation (SFG) of UV-light (λ = 355 nm) by a focused Q-switched Nd:YAG laser (f = 20 kHz, τ1064 = 10 ns, P1064 = 1.5 W) on timescales > 100 h and intensities below the damage threshold. The comprehensive study was performed with low coherence microscopy, X-ray spectroscopy (XPS), excited-state absorption (ESA) and atomic force microscopy for optical, electrical and microscopic characterization of the damages. The aim of our work is to avoid the build-up of this damage in order to extend the lifetime of LBO in UV-laser systems. As a result we found two kinds of damages: The first is a deposition of foreign material on the surface. Here, XPS uncovers several foreign elements as Na, S, Si, Ca, C depending on the composition of the ambient atmosphere during SFG. The second kind of damage is characterized by an ablation of the surface of the crystal. Only this second kind of damage disturbs the beam quality noticeably, as a strong increase of the beam propagation factor M2 was monitored simultaneously. With the results of the ESA studies we are able to discuss the role of polarons for the surface damage formation process as well as the cross-correlation of these two kinds of damages. Financial support by the DFG (TFB 13, project A5/13-04).