A I Ryasnyansky

Nonlinear susceptibilities, absorption coefficients and refractive indices of colloidal metals

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.

Investigation of nonlinear refraction and nonlinear absorption of semiconductor nanoparticle solutions prepared by laser ablation

We investigated As2S3 and CdS nanoparticle aqueous solutions prepared by laser ablation. Nonlinear optical characteristics of these solutions were studied by the Z-scan technique using Nd:YAG laser second harmonic radiation (λ = 532 nm, t = 55 ps). Nonlinear refractive indices, nonlinear absorption coefficients and third-order nonlinear susceptibilities of these solutions were measured. The comparison of nonlinear optical characteristics of As2S3 and CdS thin films and nanoparticle solutions was performed. It was shown that nonlinear refractive indices of As2S3 and CdS nanoparticles decreased with a growth in laser intensity. High nonlinear optical susceptibilities of such structures were attributed to size-related effects.

Nonlinear optical characteristics of C60 and C70 films and solutions

Abstract Investigations of nonlinear optical parameters of C 60 and C 70 films and solutions by Z -scan method are presented. Nonlinear refractive indices on the wavelength of Nd:YAG laser radiation ( λ =1064 nm) have been measured. Two-photon absorption and nonlinear susceptibilities of fullerene-doped films and solutions have been studied.

Fifth-order optical nonlinearity of pseudoisocyanine solution at 529 nm

Evidence of the interference between third- and fifth-order nonlinear optical processes is shown in the studies of pseudoisocyanine (PIC) dye aqueous solution using 529 nm radiation (t = 475 fs) and the Z -scan technique. The third-order nonlinear refractive index of the PIC solution was measured to be −8 × 10 −14 cm 2 W −1 .W e have shown th at PIC solution changes from being self-defocusing to self-focusing at high laser intensity that was attributed to the influence of fifth-order nonlinearity. The fifth-order nonlinear refractive index was measured to be 4 × 10 −24 cm 4 W −2 .T he bleaching properties of PIC solution were analysed, and the imaginary part of third-order nonlinear susceptibility was measured to be Im χ (3) =− 2 × 10 −12 esu.

Non-linear optical properties of metal nanoparticles implanted in silicate glass

Copper nanoparticles have been synthesized in silica and soda-lime glasses by 50 keV Cu þ ion implantation with doses of 8.0 � 10 16 ion/cm 2 . Nanoparticles were characterised by well developed absorption band of surface plasmon resonance in visible range. Metal nanoparticle composite glasses were analyzed by the Z-scan method at the IR wavelength of Nd:YAG laser radiation 1064 nm. The Z-scan scheme with an open and closed aperture allowed to determined non-linear refractive indices, third order non-linear susceptibilities and non-linear absorption coefficients of the synthesized materials. The third order non-linear susceptibility in the analyzed medium with simultaneous nonlinear refraction and absorption were considered as a complex values. It is suggested that the samples with non-linear absorption is perspective ones for optical limiting application. 2003 Elsevier Science B.V. All rights reserved.

Two-photon absorption and nonlinear refraction of amorphous chalcogenide films

We present the characterization of nonlinear optical parameters of chalcogenide films (As2 S3, As20 S80, 2As2 S3/As2 Se3, 3As2 S3/As2 Se3). We have measured their nonlinear refractive indices and two-photon absorption coefficients using the Z-scan method at the wavelengths of picosecond Nd:YAG laser radiation (1064 nm and 532 nm). We have analysed numerically the optical limiting of chalcogenide films due to the Kerr-induced nonlinearities, and in the case of 2As2 S3/As2 Se3 we found 12.5-fold limiting. We present the experimental results on optical limiting due to two-photon absorption. We obtained 25-fold optical limiting in the case of As2 S3. We discuss the variations of nonlinear optical properties of chalcogenide films.

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 C70-doped polyimide films and colloidal metals (Pt and Cu) are presented. The nonlinear susceptibility χ(3)(-3ω;ω,ω,ω) of the fullerene-doped film was measured to be (9±4.5)×10-13 esu (for 0.5% C70 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 I3ω(Iω) and restriction of THG efficiency in 0.5% C70-doped polyimide film. THG efficiencies were found to be 6×10-6 and 7×10-7 for 0.5% C70-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 χ(3)(-3ω;ω,ω,ω) of colloidal platinum and copper were measured to be (1.5±0.75)×10-14 and (1±0.5)×10-14 esu respectively.

Analysis of third-order nonlinear susceptibilities of quadratic nonlinear optical crystals

The relations between the tensor components of the nonlinear susceptibilities responsible for self-action processes are measured in KDP, deuterated KDP, and LiNbO3 crystals at the Nd:YAG laser wavelength (lambda=1064 nm). The measurements are conducted on the basis of the analysis of the polarization dependences of focused radiation transmittance with the z-scan scheme. The obtained polarization dependences in KDP corresponded to the fourth-rank tensor of Kerr nonlinearity. The obtained values of nonlinear refractive indices are compared with the known experimental data.

Nonlinear refraction and nonlinear absorption of As2S3 aqueous solution

We report for the first time to our knowledge on the preparation of colloidal solution of chalcogenide semiconductor As2S3 by laser ablation and the measurements of its nonlinear-optical characteristics using Z-scan method at the wavelength of Nd:YAG laser radiation (λ = 1064 nm, τ = 25 ns). The nonlinear refractive index was measured to be −7.5 × 10−18 m2 W−1. Nonlinear absorption coefficient of chalcogenide solution was measured to be 1 cm GW−1.

Analysis of third-order nonlinear susceptibilities of quadratic nonlinear-optical crystals

The values of tensor components of nonlinear susceptibilities responsible for self-action effects have been measured in quadratic nonlinear-optical crystals at the Nd:YAG laser wavelength. The angular dependences of the nonlinear susceptibilities have been determined on the base of measured relations between tensor components. The variation of the high-order nonlinear susceptibilities at various spectral ranges has been discussed. The measurements have been conducted on the basis of the analysis of polarization dependences of focused radiation transmittance in the Z-scan scheme.