Self-induced polarization rotation of laser beam in fullerene (C70) solutions

Abstract

Nonlinear self-rotation of elliptically polarized laser pulses (λ=532nm, τFWHM~12ns) in toluene, benzene and binary mixture (toluene+ethanol) solutions of fullerene C70 has been investigated experimentally. Absolute values and signs of the nonlinear refractive indices (n2) and nonlinear optical susceptibilities χ(3)(ω,−ω,ω) of C70 solutions in toluene and benzene at different values of polarization ellipse (θ=0.2÷0.8) have been determined. High-resolution transmission electron microscope studies of C70 solutions showed that in toluene+ethanol mixtures ball-shaped C70 clusters are formed with particle sizes in the range ~100÷500nm. It has been demonstrated, that the clusters sizes depend on the C70 concentration and volume fraction of ethanol in toluene. Correlation between the processes of C70 clusters formation in solutions and the values of polarization self-rotation angle of transmitted laser beam has been demonstrated. Physical mechanisms of laser induced optical activity in fullerene solutions have been discussed.