Optical limiting with C₆₀ solutions

We examine optical limiting with C₆₀ solutions for nanosecond optical pulses at 532 nm and 694 nm and microsecond pulses at 514 nm. When the input fluence is less than 50 J/cm², optical limiting is due to a combination of reverse saturable absorption (excited state absorption) and self-defocusing. Nonlinear scattering was not observed. For a peak input fluence greater than 50 J/cm², an acoustic report and broadband emission indicate that optical breakdown occurs. At 532 nm, optical limiting for C₆₀-toluene is comparable to carbon-black suspension (CBS). For use at 694 nm, C₆₀-toluene has a larger excited state absorption than at 532 nm, which partially compensates a much smaller ground state absorption. For microsecond optical pulses, C₆₀ appears to be a better optical limiter than CBS.