Synthesis and nonlinear optical properties of sol-gel materials containing phthalocyanines

Abstract

Optical limiters are devices that have the ability to limit the intensity of light that passes through them. They function like 'optical surge protectors,' blocking a greater fraction of photons when the incident light intensity is very high than when the incident intensity is low. This might allow an electronic sensor or a human eye to function under ambient lighting conditions and yet be protected from being blinded by direct laser illumination. Phthalocyanine (Pc) dyes which exhibit nonlinear optical behavior known as reverse saturable absorption (RSA) have been demonstrated to be effective in solution-based optical limiters. There is considerable interest in the possibility of fabricating optical limiters based on solid-state materials containing phthalocyanine dyes. Sol-gel processing is a solution based technique for preparing porous metal oxide monoliths at low temperatures. By adding an organic dye to the precursor solution, one can trap these organic molecules in the pores of a silica host. These potentially thermally stable materials are of interest for the fabrication of monolithic lens/limiter optical components. Our study of sol-gel synthetic approaches to phthalocyanine doped glassy materials show that phthalocyanine dyes in silica hosts are stable and exhibit optical nonlinearities comparable to those of the corresponding dye solutions.