RIGID-CAGE EFFECTS ON THE OPTICAL-PROPERTIES OF THE DYE 3,3'-DIETHYLOXADICARBOCYANINE INCORPORATED IN SILICA-GEL GLASSES

We investigated the optical properties of the saturable absorber 3,3'- diethyloxadicarbocyanine iodide incorporated in a matrix of silica gel glass by the sol-gel technique. Absorption, emission, and fluorescenc e lifetime were studied as functions of the densification procedures. With respect to the liquid solutions, we observed a strong quenching o f the P-isomer luminescence and an increase of the N-isomer fluorescen ce lifetime. These effects are ascribed to a restriction on the molecu lar photoisomerization rearrangement caused by the rigidity of the sil ica cage. Moreover, entrapping reduces intermolecular concentration ef fects. Finally, different from other glass-embedded dyes, both the abs orption and the emission are blue-shifted by about 20 nm. (C) 1997 Ame rican Institute of Physics.