Frequency conversion of picosecond radiation in fullerene-doped polyimide films and colloidal metals

Investigations of third-harmonic generation (THG) of picosecond Nd:YAG laser radiation in C-70-doped polyimide films and colloidal metals (Pt and Cu) are presented. The nonlinear susceptibility chi ((3))(-3 omega; omega, omega, omega) of the fullerene-doped film was measured to be (9 +/- 4.5) x 10(-13) esu (for 0.5% C-70 in polyimide 6B film). The influence of nonlinear refraction of fullerene-doped films on the phase-matching conditions of THG was responsible for deviation from the cubic power dependence of the third-harmonic signal on the fundamental radiation intensity I-3 omega(I-omega) and restriction of THG efficiency in 0.5% C70-doped polyimide film. THG efficiencies were found to be 6 x 10(-6) and 7 x 10(-7) for 0.5% C-70-doped polyimide film and colloidal platinum respectively. The maximal predicted efficiency of THG in 0.5% C70-doped polyimide film at weak focusing has been achieved. Nonlinear susceptibilities chi ((3))(-3 omega; omega, omega, omega) of colloidal platinum and copper were measured to be (1.5 +/- 0.75) x 10(-14) and (1 +/- 0.5) x 10(-14) esu respectively.