NONLINEAR-OPTICAL PROPERTIES OF THE FULLERENES-C-60 AND FULLERENES-C-70 AT 1.064-MU-M

Time-resolved degenerate-four-wave-mixing experiments were conducted o n films of pure C60 and C70 using a 35-ps laser at 1.064 mum. The full erenes exhibit a two-photon resonantly enhanced third-order optical re sponse that is primarily laser-pulse-limited. At high laser intensitie s, a fifth-order component to the nonlinear optical signal is observed and is attributed to a two-photon excited-state transient grating. Th e large two-photon absorption coefficients measured for C60 and C70 at 1.064 mum by nonlinear transmittance are consistent with this assignm ent.