Nonlinear optical behaviour of C60 and MWCNT suspensions far beyond the nonlinear threshold
Many carbon-based nanomaterials exhibit nonlinear optical response under intense laser radiation what makes them promising candidates for laser protection devices. They strongly attenuate intense laser light, while exhibiting high transmittance at low irradiation levels. In literature this behavior is mainly related to nonlinear absorption and nonlinear scattering. C60 and MWCNT are carbon-based materials with high optical limiting efficiency. It is generally believed that the main optical limiting mechanism of MWCNT suspensions is NL scattering whereas C60 solutions show mainly nonlinear absorption. In the case of MWCNT we observed a strong scattering signal arising near the nonlinear threshold when tested with nanosecond laser pulses at 532 nm, which is in agreement with results in literature. C60 exhibits only weak NL scattering and their OL behavior is due to NL absorption in the intermediate NL regime. In addition, we observed a diffraction pattern for high input energies, induced by local refractive index changes.