Optical limiting via nonlinear scattering with sol-gel host materials

Abstract

We describe studies of optical limiting by thermally induced nonlinear light scattering in highly porous solgel glasses. We impregnate the porous glass with a solution of reverse saturable absorber in a solvent that is index-matched to the solgel matrix at room temperature. We observe a strong enhancement of the limiting properties at high energies in the porous glass, compared to the performance of the reverse saturable absorber alone. We attribute this effect to nonlinear scattering. However, the properties of this scattering are substantially different to what was originally expected. We provide evidence that the observed effect is due to formation of gas bubbles in the focal region of the laser beam. These bubbles are trapped in the host matrix, allowing the effect to accumulate over several laser shots.