The investigations of the nonlinear optical parameters of Au, Ag, Pt and Cu colloidal solutions using the Z-scan method and third-harmonic generation (THG) are presented. The nonlinear refractive indices, nonlinear absorption coefficients and Kerr-induced nonlinear susceptibilities (χ(3)(-ω;ω,-ω,ω)) of these solutions on the wavelengths of picosecond and nanosecond Nd:YAG laser radiation (λ = 1064 nm) and its second harmonic (λ = 532 nm) have been measured. A tenfold increase of nonlinear susceptibilities on the wavelength of 532 nm in comparison with λ = 1064 nm is shown for these colloidal metals. The application of colloidal metals as optical limiters of picosecond and nanosecond radiation (λ = 1064 nm and 532 nm) was studied. The influence of aggregation of colloidal clusters on optical limiting in these media was considered. It was shown that the appearance of the long-wave wing of absorption at the final stages of aggregation led to the nonlinear absorption of picosecond pulses. The investigations of the THG of picosecond Nd:YAG laser radiation in colloidal metals (Pt and Cu) are presented. THG efficiency was found to be 7×10-7 for colloidal platinum. Nonlinear susceptibilities χ(3)(-3ω;ω,ω,ω) of colloidal platinum and copper were measured to be (1.5±0.75)×10-14 esu and (1±0.5)×10-14 esu, respectively.

The nonlinear optical characteristics of silicate glasses doped with silver nanoparticles are investigated by Z-scan technique using second harmonic radiation of picosecond Nd:YAG laser (k ¼ 532 nm, s ¼ 55 ps). The real and imaginary parts of third-order nonlinear susceptibility of silver-contained glasses were measured. It was found that the sign of Imv (3) was negative due to saturated absorption and the sign of Rev (3) was changed from negative (self-defocusing) to positive (self-focusing) with growth of laser radiation intensity. The mechanisms responsible for saturated absorption and nonlinear refraction are discussed.

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PACS 42.65. An, 42.70 Jk, 78.20.Ci Nonlinear absorption in copper-doped silicate glasses was investigated by the Z-scan technique using second harmonic radiation of a Nd : YAG laser (λ = 532 nm, τ = 55 ps). The simultaneous influence of saturated and reverse saturated nonlinear absorption processes was analyzed. The nonlinear absorption coefficient and the saturation intensity of copper-doped glasses at laser intensity of 5.4 × 10 9 W cm -2 were measured to be 6 × 10 -6 cm W -1 and 4.3 × 10 8 W cm 1 Introduction Nonlinear optical properties of the structures containing metal nanoparticles (MN) are of great interest due to their possible applications in optoelectronics and laser physics. Silver, gold, cobalt, platinum, and copper nanoparticles were the mostly investigated MN, as dispersed in various insulator matrices. Several mechanisms contribute to the third-order nonlinearities in small metal nanoparticles, including surface plasmon resonance (SPR) enhancement, intraband transitions in the quantum confined conduction band (quantum size effect), interband transitions between the d band and the conduction band, and nonequilibrium electron heating. The efficiency of the nonlinear optical response of such materials depends on the MN concentration [1]. The nanoparticles-containing composite materials have short response time and high Kerr nonlinear susceptibility and can be used as ultra-fast optical switchers and limiters.As it was shown in earlier studies of copper nanoparticles embedded in insulator matrices, the tendency was to investigate the influence of MN size and preparation methods [2,3] on their nonlinear refractive index [4], third-order nonlinear susceptibilities and time response [5]. At the same time, such materials possess the enhanced nonlinear absorption properties, in particular negative nonlinear absorption (NNA), i.e. saturated absorption, and positive nonlinear absorption (PNA), i.e. two-photon absorption and/or reverse saturated absorption, especially in the vicinity of the SPR spectral range of the nanoparticles. Recently we have analyzed these nonlinear optical properties as well as the nonlinear refraction in silver-and copper-doped glasses in the spectral ranges far from their SPRs (in UV [6] and IR [7] ranges).In the present note, the results of nonlinear absorption studies regarding the copper nanoparticles embedded in silica glasses by ion implantation and using laser radiation (λ = 532 nm) near the SPR of these MN are presented.