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

Investigations of third-harmonic generation (THG) of picosecond Nd:YAG lase r radiation in C-70-doped polyimide films and colloidal metals (Pt and Cu) are presented. The nonlinear susceptibility chi ((3))(-3 omega; omega, omeg a, 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 re fraction of fullerene-doped films on the phase-matching conditions of THG w as responsible for deviation from the cubic power dependence of the third-h armonic signal on the fundamental radiation intensity I-3 omega(I-omega) an d restriction of THG efficiency in 0.5% C70-doped polyimide film. THG effic iencies were found to be 6 x 10(-6) and 7 x 10(-7) for 0.5% C-70-doped poly imide film and colloidal platinum respectively. The maximal predicted effic iency of THG in 0.5% C70-doped polyimide film at weak focusing has been ach ieved. Nonlinear susceptibilities chi ((3))(-3 omega; omega, omega, omega) of colloidal platinum and copper were measured to be (1.5 +/- 0.75) x 10(-1 4) and (1 +/- 0.5) x 10(-14) esu respectively.