Enhanced optical limiting in derivatized fullerenes

Transient absorption measurements are shown to be useful in predicting spectral regions of interest for potential optical limiters. For both C60 and 6,6-phenyl-C61-butyric acid cholesteryl ester, differential transmission measurement predicts enhanced limiting at longer wavelengths, which have been experimentally confirmed in direct optical power limiting measurements. However, despite, this enhancement, the utility of C60 in this range is limited by the low ground-state population achievable. To exploit the large excited-state cross section requires either higher solubility or an extension of the ground-state absorption into the red. The addition of a solubilizing chain across a 6-6 bond accomplishes both of these goals. Use of this solubilized derivative of C60 also facilitates preparation of controlled-concentration-doped solgel glasses. This will permit control of the concentration profile of the active material in high-damage-threshold transparent hosts, which will be a crucial damage feature of optimized optical power limiting geometries.