Resonant optical nonlinearity of fullerenes in free-standing polymethyl methacrylate films

Abstract
We have prepared films of polymethyl methacrylate in which fullerenes (a mixture of C60 and C70) are uniformly embedded. By performing both degenerate four-wave mixing experiments and irradiance-dependent transmission measurements with nanosecond laser pulses of 608-nm wavelength, the third-order nonlinear optical susceptibility of these films is determined to be of the order of 10−10 esu. This susceptibility is dominated by its imaginary part. Excited-state absorption is the main mechanism responsible for the observed nonlinear susceptibility.