OPTICAL-PROPERTIES OF PR3-GEL GLASSES OBTAINED BY SOL-GEL METHOD( DOPED SILICA)

Thermally densified silica glasses doped with Pr3+ ions were prepared by sol-gel method. Three procedures of synthesis are described. Absorp tion, emission and excitation spectra of Pr3+ doped silica glasses obt ained by sol-gel method are reported. We found on the basis of now pre sented results and those earlier reported that intensities of the abso rption bands of Pr3+ change with concentration nonlinearly, especially in the range of H-3(4) --> P-3(2); P-3(0) and D-1(2) transitions. Thi s phenomenon could be caused by clustering, which leads to cooperative interactions. On the basis of the absorption spectra measurement, the energy level diagram was prepared which helps in the explanation of t he emission properties of glasses synthesized by different techniques. The luminescence spectra were dependent on excitation wavelength. The spectra excited in high UV range exhibited, except emission in the re d range corresponding to the D-1(2) --> H-3(4) transition, a broad ban d emission with characteristic holes at the envelope corresponding to the P-3(2), (P-3(1), I-1(6)) and P-3(0) terms. Nature of this broad ba nd emission is discussed. The observed holes result from reabsorption processes, which are controlled by concentration bf active ions. Mecha nism of their occurrence remains unknown. No emission from P-3(0) leve l was observed for some kind of glasses, for another one the emission from D-1(2) and P-3(0) levels was detected. (C) 1998 Elsevier Science B.V. All rights reserved.