Second harmonic generation optimization in thermally poled borophosphate glasses and characterization by XANES and XPS

Second harmonic generation (SHG) in poled glasses opens new opportunities i n material research and device development for optics. SHG results that rel ate to thermally poled new borophosphate glasses have been analyzed. By a c ycling poling-depoling process an optimization of the SHG response can be o btained. As the signal is localized near the surfaces in contact with the e lectrodes during poling, XPS and X-ray absorption near-edge spectroscopy (X ANES) spectroscopies have been performed to characterize cathodic and anodi c surfaces of these glasses before poling, and after poling or depoling tre atments. Structural differences are observed by XANES at the O K-edge after poling on both surfaces. Moreover. an accumulation of Na+ mobile cations i s evidenced on the cathodic surface by XPS spectroscopy confirming the migr ation of Na+ mobile cations after the glass has been submitted to high de f ield. Finally, the XPS and XANES investigations of poled glasses evidences some breakage of phosphate chains in the glass network which occur during t he poling treatment. Conversely, bridging bonds are partly restored after t hermal depoling. (C) 2000 Elsevier Science B.V. All rights reserved.