Enhancement of second-order optical susceptibilities of Er doped germanate glasses

During bicolor optical treatment by two coherent laser beams from 25 ps Erbium-glass laser (lambda=1.54 mu m), we have established substantial increase of effective optical second-order susceptibility near the critical temperature points corresponding to the glass structural transformation near 435 degrees C. The increasing Er3+ content favors substantial increase of the photoinduced optical second harmonic generation (SHG). This temperature dependence of the second-order optical susceptibilities detected by the SHG correlates well with the differential scanning calorimetric (DSC) measurements. At the same time, the effect exists only in a narrow temperature range (up to 12 degrees C). There was not temperature hysteresis. Possible physical mechanisms of the phenomenon observed are discussed. (c) 2006 Elsevier B.V. All rights reserved.