Study of nonlinear optical characteristics of various media by the methods of z-scan and third harmonic generation of laser radiation

The nonlinear optical parameters of colloidal solutions of metals, semiconductor chalcogenide films, vapours and solutions of organic dyes, as well as of fullerene-doped polyimide films are studied by the methods of z-scan and third harmonic generation (THG). The nonlinear refractive indices, nonlinear susceptibilities, and nonlinear absorption coefficients of these materials are measured at the fundamental 1064-nm emission wavelength of a 35-ps pulsed Nd:YAG laser and its second harmonic at 532 nm. The study of the optical limitation of picosecond and nanosecond light pulses in these media showed that the appearance of the long-wavelength absorption band at the final stage of aggregation of colloidal metals resulted in nonlinear absorption of picosecond pulses. The nonlinear susceptibilities χ⁽³⁾(-3ω,ω,ω,ω) of colloidal metals, fullerenes, and dye vapours are measured by the picosecond THG method, and the effect of self-action on THG in these media is analysed.