Optical limiting with higher fullerenes

Optical limiting has been investigated for higher fullerenes and compared with C₆₀. The transmission through an aperture placed after solutions of C₇₆, C₇₈, and C₈₄ in tetrahydronaphthalene was measured using Q-switched laser pulses with a wavelength of 532 nm and a pulse width of 8 ns FWHM. Unlike C₆₀, the transmission for these higher fullerene solutions decreased linearly with increasing optical pulse energy. We attribute the linearized optical limiting response to self-defocusing of the optical beam and the absence of excited-state absorption. The ground state absorption spectra for the higher fullerenes suggest their use for optical limiting in the near infrared, and the C₈₄-tetrahydronaphthalene solution was found to be an optical limiter at 1.064 m.