Third-order nonlinear optical properties of metal dithiolene- and phthalocyanine-doped sol-gel materials

Recent studies on metal dithiolene complexes in solution and PMMA have shown this range of materials to exhibit high third-order nonlinear optical coefficients, (Chi) 3 , and excellent figures of merit. Phthalocyanine dyes have been shown to exhibit optical limiting due to the nonlinear effect of reverse saturable absorption. We report here on the third-order nonlinear optical characterization of several metal dithiolene and phthalocyanine compounds doped in sol-gel derived materials. These hosts provide a physically and chemically stable environment for the nonlinear compounds, and offer the potential of high levels of doping. The dithiolene and phthalocyanine compounds were incorporated into partially densified sol-gel silica glass (xerogels) by the post-doping technique, and into the hybrid organic-inorganic materials at the sol-stage. To obtain optical quality surfaces on the porous xerogel, a unique polishing technique has been developed. Picosecond and nanosecond pulsed laser studies of nonlinear refraction and absorption are presented, together with laser damage and micro-hardness measurements. For the dithiolenes, concentrations of the order of 10 18 molecules/cm 3 for both the hybrid material and the xerogel were studied using the degenerate four wave mixing (DFWM) technique. (Chi) 3 values up to 1.4 X 10 -19 m 2 /V 2 (equivalent to 1.0 X 10 -11 esu) were observed in the sol-gel host.