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The Z-scan experiment is the fastest method to determine non-linear optical (NLO) coefficients of materials. Classic Z-scan technique described by Sheik-Bahae et al. (1989) and Wang et al. (1994) uses pulsed or CW lasers with the Gaussian beam profile. As long as the Gaussian profile is not diffused by the examined materials, this method can be used. However, by extending the classic Z-scan technique using a CCD beam profiler and analyzing the beam deviation from the Z axis, the NLO coefficients can be estimated even for a highly diffused Gaussian beam. The method proposed in this paper tracks the centroid position of the diffused beam and on this basis the two photon absorption coefficient β and the nonlinear refractive index n 2 are obtained. The accuracy depends on the samples geometry and the CCD detector used. The new approach presented in this paper can be used in substitution to the classic technique for the materials which strongly diffuse the Gaussian beam.

This paper reports the second- and third- order nonlinear properties of Er3+/Yb3+ -doped PbO-GeO2-Ga2O3 glasses with Au nanoparticles. The glasses were prepared by the melt-quenching technique, followed by annealing for the nucleation of gold nanoparticles. A 200 kV high-resolution transmission electron microscope (HR-TEM) was used to verify the presence of Au nanoparticles and estimate their sizes. The role of annealing on the possible variation of the third-order nonlinear electric susceptibility is studied in details following the possible changes in the Au nanoparticle concentration. Two-photon absorption (TPA) coefficient (β) and nonlinear refractive index (n2) was measured by the conventional Z-scan method at 532 nm wavelength. The highest values were obtained for the sample with gold nanoparticles annealed for 52 h. Second harmonic generation (SHG) measurements were also performed and showed low conversion efficiency.

A series of lithium niobate LiNbO3 (LN) single crystals doped with Er3+ were grown under the same conditions by melt-quenching method. The distribution coefficients of rare-earth (RE) elements in the ”crystal-melt” system of LN were determined at the beginning of the crystal growth. Their dependence on the dopant concentration in melt for 0.4 and 0.8 wt % was investigated. The procedure is applied to RE-doped lithium niobate (LiNbO3), a material of great interest for optoelectronic applications. We have obtained the real χ R ( 3 ) and imaginary parts χ I ( 3 ) of the third-order, nonlinear optical susceptibility to the nonlinear refractive index n2 and the nonlinear absorption coefficient β that are valid for absorbing systems. We show that nonlinear refractive or absorptive effects are the consequence of the interplay between the real and imaginary parts of the third-order susceptibilities of the materials. The method for measuring non-linear absorption coefficients and nonlinear refractive index based on well-known Z-scan is presented.

Studies of third-order nonlinear optical phenomena on Yb 3+ /Tm 3+ co-doped PbO-GeO 2 glasses containing different concentration of silicon nanoparticles are presented. The well-known melting-quenching technique was used for the production of the samples. Measurements were performed using conventional Z-scan, SHG and ESHG methods with Q-switched mode-locked ns scale Nd-YAG lasers, intensities in the 0.8–1.2 GW/cm 2 power density range and repetition rate of 10 Hz. Maximum third-order susceptibilities and second harmonic generation were found for the sample prepared with 1 wt% of Si powder.

Composites containing nanocrystallites of novel rare earth doped borate δ-BiB3O6 and polyvinyl alcohol (PVA) polymer are reported. Experimental studies of the third-order nonlinear refractive index n2, absorption coefficient β and second-order nonlinearity for δ-BiB3O6:Pr3+(7.5 at.%) large-size nanocrystallites embedded into PVA polymer matrices and deposited on gallium-doped zinc oxide substrates modified with silver nanoparticles (Ag-NPs) using Z-scan technique and second harmonic generation (SHG) method were performed. The complex SHG and Z-scan measurements for different sizes of Ag-NPs were done. It was shown that the polymer composite of PVA containing particles of orthorhombic bismuth triborate doped with praseodymium (7.5 at.%) reveals optically nonlinear response. It was shown that the studied composites possess both coherent and non-coherent component of nonlinear optics. The Z-scan measurements were done with use of 5 ns Nd:YAG laser and the second harmonic generation was measured using the 25 ns Nd:YAG laser with frequency repetition about 10 Hz. The measurements showed that both second as well as third-order susceptibilities are sensitive to the sizes of the Ag-NPs. The obtained results confirm a principal role of the Ag-NPs in influencing the output susceptibilities.

The topography of indium tin oxide (ITO) films with incorporated silver nanoparticles and irradiated by single pulses of 18 ns Nd:YAG laser has been investigated. The study was carried out with two Ag/ITO films having resistances of 50 Ω and 4 Ω/square sheet resistances. The periodic structures in both samples were created after the laser treatment. The photo-induced periodic structures have a different character while the sheet resistance plays a major role in the growth process of these structures. The results of optical and non-linear optical investigations lead us to the conclusion that the temporary polarization of samples and high temperature of illuminated spot during laser treatment is responsible for the shape of periodic structures. This conclusion has been also confirmed by local permittivity measurements using evanescent microwave microscope and theoretical calculations concerning the temperature distributions during laser illumination.

We have found photoinduced second harmonic generation at wavelength 1064 nm during bicolor Nd:YAG laser coherent treatment of TeO2–ZnO and GeO2–PbO amorphous films. The maximally achieved second order susceptibility was equal to about 1.02 pm/V. Correlation of the induced second order susceptibility with local sample heating and induced birefringence may indicate an occurrence of local phase transitions from amorphous glass-like phase to non-centrosymmetry metastable phases.

The topography of indium tin oxide (ITO) films with incorporated silver nanoparticles and irradiated by single pulses of 18 ns Nd:YAG laser has been investigated. The study was carried out with two Ag/ITO films having resistances of 50 Ω/ITO sheet and 4 Ω/ITO sheet. The periodic structures in both samples were created after the laser treatment. The photo-induced periodic structures have a different character while the sheet resistance plays a major role in the growth process of these structures. The results of optical and non-linear optical investigations lead us to the conclusion that the temporary polarization of samples during laser treatment is responsible for the shape of periodic structures.

A new promising organic chromophore for two-photon laser absorption at 1064 nm with 1,4-diethoxy-2,5-bis[2-(5-methylthien-2-yl)ethenyl]benzene (A-C) was synthesized. We have performed evaluations of the two-photon absorption for these chromophores incorporated into the polymer matrices. Following the obtained quantum chemical data, we have performed quantum chemical simulations of the third-order susceptibilities for the investigated chrompophore incorporated into the PMMA matrices. The calculations were done within the three-level model. We have established that the experimentally calculated data are a bit less than theoretically calculated; however, the general tendency of their changes shows a good coincidence. The maximally achieved value of the TPA is equal to about 59.2 cm/GW at wavelength 1064 nm, which, together with their high photothermal stabilities, make them good candidates for optical-limiting processes.

We have studied thin nanolayers (with thicknesses of about 1–2 nm) between In2O3:Sn (indium–tin oxide (ITO)) crystalline films and glass substrates using the photo-induced optical second harmonic generation (PISHG) method. The maximal PISHG response observed for the pump–probe delay times was about 26 ps. The performed experimental measurements and quantum chemical theoretical simulations show that the observed effects are caused by two factors. The first is caused by the film–glass interface potential gradient and the second is a consequence of additional trapping levels appearing in the energy gap, particularly due to Sn doping. PISHG may be considered as a sensitive tool for such kinds of semiconductors.

We have established a principal role of the polarity of polymer matrices on the piezooptical dispersion of the γ-glycine nanocrystallites embedded into the polymethymethacrylate (PMMA) and polycarbonate (PC) matrices. We found that the optical treatment by bicolor two laser beams at 1064 nm and 532 nm which are originating from the same 10 ns Nd:YAG laser, causes occurrence of the piezooptical effects. The optimal content of the γ-glycine nanocrystallites with respect to the magnitude of piezooptical coefficients was within the range of size 50–80 nm, corresponding to the 6.5 wt.%. We studied relaxation and spectral dependence of the corresponding coefficients of the piezooptic tensor.

We have observed a several times enhancement of the optical second harmonic generation in newly synthesized Europium doped PbO–Bi2O3–Ga2O3–BaO glasses for the fundamental wavelength 1320 nm during optical treatment by coherent fundamental and doubled frequency beams with a pulse duration about 15 ns. We have found that the maximal optical second harmonic generation was achieved for the Eu content of about 1.4% at fundamental beam average power equal to about 3 GW/cm2 , temperature of about 300 K and intensity ratio between the fundamental and doubled frequency beams of about 9. Frequency repetition of the optical pulses was equal to about 10 Hz. It was shown that doping by other rare earth ions, particularly by Dysprosium does not give a sufficient contribution to the effect.

The Z-scan measurements for the non-centrosymmetric optical crystals β-BaTeMo 2 O 9 (BTMO) were performed. The corresponding experiments were carried out using the 5 ns pulses of the second harmonic of a nanosecond Nd:YAG laser at the 532 nm wavelength. It was shown that the studied crystals possess promising third-order optical susceptibilities, which allow to use the crystal as optical limiters. The comparison with other oxide materials is presented. To clarify the origin of the observed effect, the electronic and optical properties of BTMO were calculated using the density functional theory (DFT)-based method. The performed calculations of the electronic and optical properties revealed certain peculiar features that can be suitable for the nonlinear optical applications. The relation between the observed nonlinear optical features and the calculated band structure is emphasized. The values of the calculated band gap and refractive index for β-BaTeMo 2 O 9 are also reported.

International audience; Palladium nanoparticles deposited on SnO2-doped In2O3 substrate show substantial optical second harmonic generation (SHG) in the spectral range (λ = 120–160 nm) which is a part of the vacuum ultraviolet (VUV) spectrum. A single crystalline Li2 B4 O7 optical parametric generator (OPG) pumped by nanosecond xenon–fluorine excimer laser (EMG 500/218 (Lambda Physics)) with the wavelength 218 nm, pulse duration about 6–8 ns; pulse rate about 80 hz, average pulse power about 0.2 MW and beam diameter varying within the 1.3–7.5 nm was used to form the fundamental beam. The OPG Li2 B4 O7 single crystal was cut in the XZ optical plane. We have tuned the fundamental wavelengths within the 250–320 nm spectral range varying the angle of the plane with respect to the incident pumping beam. Maximal SHG output (in the reflected SHG geometry) is observed for the incident angles 75○–80○ with respect to the surface normal and p-polarized incident fundamental ultraviolet beams. Spectral separation between the vacuum ultraviolet (VUV) SHG intensities and the fundamental beams was performed using a VUV Seya-Numioka vacuum monochromator with spectral resolution 6 nm in the investigated spectral range. We have found that decreasing mean average palladium nanoparticle sizes favour substantial enhancement of the output SHG within the 120–160 nm spectral range. A layer of platinum nanoparticles coated on a layer of palladium nanoparticles suppresses the SHG effect indicating a quenching of the surface plasmon excitation originating from the palladium nanoparticles. The observed effect allows utilizing the palladium nanoparticles as an efficient material for frequency transformation of the UV nanosecond pulses (spectral range 240–310 nm) into the nanosecond laser pulses with wavelengths 120–160 nm.