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Abstract: ZnF2–PbO–TeO2 glasses doped with different concentrations of TiO2 were synthesized and subsequently crystallized. The prepared samples were characterized by XRD, SEM and DSC. IR, ESR and optical absorption were studied to explore the influence of titanium valance states and their coordination with oxygen on structural and optoelectronic aspects of the samples. These studies have indicated that there is a possibility for the titanium ions to exist in Ti3+ and Ti4+ states in these glass ceramics and participate in the glass network forming. Finally, we have undertaken second harmonic generation (after the samples were dc field treated at elevated temperatures) with 10ns Er3+: glass laser (of wavelength 1540nm with power densities up to 1.5GW/cm2) and birefringence studies (in the wavelength range 420–750nm) to examine the suitability of these materials for optically operated devices. The results of non linear optical studies were discussed in the light of nature of different micro/nano crystallites ingrained in the glass ceramic samples. [Copyright &y& Elsevier]

Abstract: Two methods of phase transition detection — non-linear optical based on optical poling (second harmonic generation) together with traditional, calorimetrical, Differential Scanning Calorimetry are compared. The investigations are performed near glass transition and melting point. As examples germanate GeO2–PbO glasses doped by Er+3 ions are chosen. It is demonstrated that although both methods give an evidence of the transitions the non-linear optical one is much more sensitive. A short description of the experimental set-up for the optical measurements and physical aspects of the method are given. [Copyright &y& Elsevier]

Abstract: The non-linear optical response of sulphide glass-containing β-GeS2 microcrystallites, has been studied at a fundamental wavelength of λ=5.5μm under additional irradiation by IR-pulses of λ=3.7μm. A substantial increase of the non-linear susceptibility with IR-power and size of the microcrystallites has been found. Molecular dynamics calculations linked to quantum chemical calculations show that this effect could be explained by substantial contributions of the microcrystallite interfaces and due to the phonon sub-system. The role of anharmonic electron–phonon effects is experimentally confirmed by the observation of an optimal delay of 8ps between the pump laser pulses at 3.7μm and the probing laser pulses at 5.5μm, which generate the observed second harmonic signal. [Copyright &y& Elsevier]

Abstract: It was revealed that photoinduced non-linear optical methods may be used as a sensitive tool for investigations of low temperature semiconductor-isolator phase transformation. This was experimentally demonstrated using a method of photoinduced optical second harmonic generation, where the photoinducing regime was done by polarized nitrogen laser. The physical insight of the method is explained by the interaction of polarized optical field with boson sub-systems (phonon and magnons) near temperature of the phase transformation. Comparing low temperature dependence of specific heat for Pb1−x YbX (X=S, Se, Te) with the ones for the photoinduced non-linear optical methods we have found substantially better temperature recognition of corresponding phase transformations and the output non-linear optical signal is inversely proportional to the heat capacity renormalized by temperature — C p / T. The obtained results demonstrate high sensitivity of the photoinduced SHG to the low temperature phase transformations. [Copyright &y& Elsevier]

Abstract: Photoinduced optical second harmonic generation (PISHG) and differential scanning calorimetry (DSC) methods were used for study of tetraethyl-ammonium (TEA)–CoCl2Br2 ferroelectric nanocrystallites (about 50nm) near melting point. It was shown that PISHG is more sensitive to melting temperature compared to the DSC. This is caused by sensitivity of PISHG due to contribution both of ground electron states as well as of excited ones contrary to the DSC method where principal role is played by ground states. [Copyright &y& Elsevier]

Abstract: A large effective second-order optical susceptibility equal to about 52pm/V for ZnO films with thickness about several μm deposited on MgO substrate by molecular epitaxial method was achieved using a bicolour coherent treatment by a pulsed 1.32μm Nd–YAG laser and its second harmonic at λ =0.66μm. The written grating was stable during 24 days and its optical susceptibility decreased not more than 26% with respect to the initially written one after interruption of optical treatment. The same measurements performed for the ZnO films deposited by metaloorganic chemical vapor deposition, pulsed laser ablation and spray pyrolysis have shown that the output optical susceptibility is at least half order less. The temperature dependences of the second order susceptibilities have shown that it achieves a maximum near a temperature of 261K. Other methods do not show substantial temperature dependences. We have found that maximal second harmonic generation signal was achieved for the films with thickness of about 2.75μm. [Copyright &y& Elsevier]

Photoinduced optical and second-order non-linear optical effects in the interfaces separating In2O3–SiON (O/N ratio equals 1) films doped with A1, Sn and glass substrates were investigated using the photoinduced optical second harmonic generation. The photoinduced effective second-order optical susceptibility deff (at λ=1.76 μm) shows a good correlation with the linear optical susceptibility, particularly with the shift of the absorption edge. The maximal response of the photoinduced optical response signal was observed for the pump–probe delaying time of 34 ps. The performed experimental measurements indicate that the observed effects are mainly caused by the interface potential gradients on the border glass–In2O3–SiON film and by additional polarization due to insertion of the Al and Sn atoms. The observed phenomenon may be proposed as a sensitive tool for investigation of thin semiconducting interfacial layers and simultaneously such films may be used as materials for non-linear optical devices. [Copyright &y& Elsevier]

Contribution of the hexagonal-like structural components to the photoinduced second harmonic generation (SHG) in GaN large-sized nanocrystallites (with sizes about the 10–30 nm) incorporated into the polyvinylalcohol photopolymer matrices is revealed. The SHG measurements were done using pulsed Nd:YAG laser beam (λ=1.06 μm; pulse duration τ=15–50 ps, laser power about 30 MW) as a fundamental ones and a picosecond nitrogen pulsed laser (P=10 MW; λ=0.377 μm; pulse time duration τ=10–25 ps) as a photoinducing one. We have found that with increasing pumping power density the SHG output signal increases and achieves its maximum value for the power density about 2.6 GW/cm2 per pulse. The maximal output photoinduced SHG signal was achieved for parallel directions of the pumping and fundamental beam polarizations. The maximal values of the second-order nonlinear susceptibilities were equal to about 1.09 pm/V. We have observed an increase of the output SHG below 30 K and for pump-probe delaying time about 18 ps. Substantial contribution to the SHG of wurtzite-like (hexagonal) structural fragments is shown. [Copyright &y& Elsevier]

A new method of monitoring the superconductivity in the Hg-1201 films is proposed using the photoinduced optical second harmonic generation (PISHG). In the present work the experimental PISHG results are presented for the Hg-1201 films deposited on the MgO substrates. We have found that the PISHG is more sensitive compared with the traditional methods (resistivity, magnetic susceptibility, etc.). Using of the pump–probe technique allows obtaining additional parameters of the carrier relaxation responsible for the superconductivity. The proposed method has an advantage compared with the others because they are contactless and non-invasive and give a possibility to detect the phase transitions with higher precision. [Copyright &y& Elsevier]

The effective nanometer-sized thin layer (about 1–2 nm) located between a crystalline ZnS film and glass substrate is studied here using photoinduced optical and second-order non-linear optical (second harmonic generation (SHG) and electrooptics effects) techniques. A photoinduced shift of the effective energy gap is found for the first time in ZnS films doped with the same amount (4 at.%) of different elements, namely, In, Al and Sn. The photoinduced second-order non-linear optical properties (linear electrooptics (LEO) and SHG) of the specimens show a good correlation with the corresponding features of the linear optical susceptibilities, particularly, the imaginary part of dielectric susceptibility near the absorption edge. The maximal response of the photoinduced signal is observed for the pump–probe delaying time of about 20 ps. The performed experimental measurements indicate that the observed effects are stimulated by two factors: the first one is connected with the interface potential gradients at the glass–ZnS film boarder; the second one is a consequence of the additional polarization due to the insertion of Al, In and Sn atoms. The observed phenomenon may be proposed as a sensitive tool for investigation of thin semiconducting-glass interface layer. Moreover, such nanolayers may be applied in quantum electronic devices. [Copyright &y& Elsevier]

Examines the use of YAG-Nd3+ laser to measure second-harmonic generation (SHG) in cerium-doped YBa2Cu3O7-delta ceramics at low temperatures. Dependency of SHG signal on temperature; Effects of ceramic YBA2Cu3O7-delta on reflected SHG; Application of nonlinear optics methods for high-temperature superconductors.

Highlights: [•] New type of optically operated rare earth doped borates is proposed. [•] Principal role of the pho9non subsystem in photoinduced electrooptics, SHG and piezooptics is shown. [•] The possibility to create the laser operated materials is shown for the such kind of sold state alloys. [ABSTRACT FROM AUTHOR]

Photoinduced and second-order optical effects in the interfaces separating InBr (IB) films doped by Al, In, Sn and bare glass substrates were investigated using the photoinduced optical second harmonic generation. The second-order optical susceptibilities (at λ=1.76 μm) show a good correlation with the shift of the absorption edge. The maximal response of the photoinduced response signal was observed for the pump-probe delaying times equal about 32 ps. The measurements indicate that the observed effects are caused by two cases: by interface potential gradients on the border glass-IB and by polarization of the medium due to impurities. The observed phenomenon may be proposed as a sensitive tool for investigations of thin nanointerfaces appearing between the glass substrate and crystallite layers. [Copyright &y& Elsevier]

Photoinduced optical and second-order non-linear optical effects in nanolayers separating indium oxide (In2O3) crystalline films doped by Al, Sn, and glass substrates were found. Photoinduced optical second harmonic generation was applied as a particular non-linear optical method. The photoinduced second-order non-linear susceptibilities (at λ=1.76 μm) show good correlation with the photoinduced linear optical susceptibilities, particularly with the optical absorption. The performed experimental measurements show that the observed effects are caused by two factors. The first one is related with the potential gradient on the glass–In2O3 film border. The second one is caused by additional polarization due to doping by the Al and Sn atoms. Such near-the-border nanolayers can be considered as new type of second-order optical materials. [Copyright &y& Elsevier]

Photoinduced second harmonic generation (SHG) in Bi2Se3–CaBr2–PbCl2 optical fibers have been studied using experimental and theoretical quantum chemical and molecular-dynamics methods. Infra-red (IR) induced SHG was measured in the IR region within the 5.5–21 μm. CO laser (λ=5.5 μm) was used as a source of the photoinducing IR light. The glasses had diameters varied within the 5–35 μm. The lengths of the fibers varied from 0.5 cm up to the 1.4 m. We have found that with increasing photoinducing power, the SHG for the doubled frequency 5.3 μm of the CO2-laser increases and achieves its maximum value at photoinducing power 1.35 GW/cm2 per pulse. The maximal by achieved values of the second-order nonlinear optical susceptibilities d222 was equal about 1.5 pm/V. With decreasing temperature, the SHG signal strongly increases within the 75–220 K temperature range. Picosecond probe–pump measurements indicate on the occurrence of the SHG maximum at pump–probe time delay about 25 ps. These dependencies we explain within a framework of the quantum chemical approach taken into acount photoinduced anharmonic electron–phonon interactions. We have found that Bi–Se tetrahedral bonds play a key role in the observed IR photoinduced nonlinear optical (NLO) effects. The obtained results show that the mentioned glasses may be applied as materials for IR picosecond–second quantum electronics. [Copyright &y& Elsevier]

Abstract: Enhancement of the second-harmonic generation (SHG) efficiency has been observed in nanocrystallites of ferroelectric Sr6Ti2Nb8O30 and Sr6Ti2Ta8O30. The enhancement was observed in particle sizes below 150 nm. The particles were incorporated, with an applied electric field, into a photopolymer polyvinyl alcohol matrix. The maximum SHG output was achieved with a nanocrystallite content of about 4.2%, with respect to mass. An increase of the second-order optical susceptibility, to about 3.2 pm/V and 2.4 pm/V for Sr6Ti2Nb8O30 and Sr6Ti2Ta8O30 respectively, was observed with a decrease in particle size from 250 nm to 70 nm. [Copyright &y& Elsevier]

Abstact Phase diagram of the Tl 3 PbBr 5 –Tl 3 PbI 5 section of the reciprocal system 2TlI + PbBr 2 ⇔2TlBr + PbI 2 was investigated by differential thermal and X-ray phase analysis methods on 18 alloys. The section is quasi-binary, of eutectic type, with the invariant point coordinates 76 mol% Tl 3 PbI 5 and 355 °C. The addition of Tl 3 PbI 5 results in stabilization of the high-temperature (HT) modification of Tl 3 PbBr 5 forming a substitution solid solution, which at room temperature occupies the concentration range of ∼9–71 mol% Tl 3 PbI 5. The solid solution range of low-temperature (LT) Tl 3 PbBr 5 is minor (0–∼6 mol% Tl 3 PbI 5), and that of Tl 3 PbI 5 is in the range of ∼71–100 mol% Tl 3 PbI 5. Tl 3 PbBr 2.5 I 2.5 crystals were grown by Bridgman-Stockbarger method; they belong to wide-gap semiconductors with E g decreasing from 2.45 eV at 100 K to 2.36 eV at 300 K. Based on X-ray photoelectron (XP) core-level spectra, one can conclude that the Tl 3 PbBr 2.5 I 2.5 crystal reveals the XP fine-structure peculiarities well ascribed to thallium, lead, bromine and iodine, constituent atoms of the quaternary halide under consideration. Treatment of the Tl 3 PbBr 2.5 I 2.5 crystal with 3 keV Ar+ ions reveals that the Pb–I bonds are somewhat weaker in this compound, as compared to the Pb–Br, Tl–Br and Tl–I bonds. Comparison with the similar XP measurements of the related ternary bromide and iodide (Tl 3 PbBr 5 and Tl 3 PbI 5) indicates that the positive effective charge of lead atoms gradually decreases when going from Tl 3 PbBr 5 to Tl 3 PbBr 2.5 I 2.5 and, further, to Tl 3 PbI 5 , while the charge state of thallium atoms does not change in the above sequence of compounds. In the sequence Tl 3 PbBr 5 → Tl 3 PbBr 2.5 I 2.5 → Tl 3 PbI 5 the relative peak intensity of the XP valence-band spectrum monotonously decreases. The laser stimulated piezooptics at 1150 nm excited by 1540 nm Er:glass nanosecond laser and its second harmonic generation are reported. Graphical abstract Image 1 Highlights • Phase diagram of Tl 3 PbBr 5 –Tl 3 PbI 5 section of 2TlI + PbBr 2 ⇔2TlBr + PbI 2 system is studied. • Tl 3 PbBr 2.5 I 2.5 single crystals have been grown by Bridgman-Stockbarger method. • Electronic structure of the Tl 3 PbBr 2.5 I 2.5 crystal is studied by XPS and XES methods. • Tl 3 PbBr 2.5 I 2.5 is a semiconductor: E g decreases from 2.45 eV at 100 K to 2.36 eV at 300 K. • Effects of laser stimulated piezooptics are explored for Tl 3 PbBr 2.5 I 2.5 [ABSTRACT FROM AUTHOR]

Abstract Complex studies of the photoconductivity, photoinduced second harmonic generation (SHG) and linear electrooptic for four quaternary chalcogenide crystals Ag 2 In 2 GeSe(S) 6 and Ag 2 In 2 SiSe(S) 6 that crystallize in the monoclinic structure have been done in the infrared spectral range. As a photoinduced beam we have used a bicolor coherent 9400/4700 nm laser beam of microsecond pulsed CO 2 laser. The electrooptical effect was probed by continuous wave He-Ne laser at wavelength 3390 nm and second harmonic generation by nanosecond pulse Er:glass laser at wavelength 1540 nm. The relation between the energy gap, output electrooptic efficiency and the photo stimulated SHG has been done. The detailed kinetics of the photoconductivity show that there occurs significant re-distribution of photoexcited carriers between the defects. This factor also may play a crucial role both for the photoinduced electrooptic as well as for second harmonic generation. It was experimentally shown that there exists an increase of the second-order susceptibility with enhanced electronic energy gap which contradicts compared to the generally adopted approach. Such extraordinary behavior is a consequence of the significant contribution of anharmonic phonons in the infrared spectral range spectrally situated near the nonlinear optical resonances. Additional role here may also belong to the space re-distribution of carriers between the defects that was established following the photoconductivity kinetics studies. [ABSTRACT FROM AUTHOR]

Abstract The photophysical properties of donor-acceptor based benzoxazoles were investigated by means of steady-state and time-resolved fluorescence techniques. Additionally, laser stimulated second-order optical effects (preliminary second harmonic generation (SHG) were studied. The studies show that the nitro-benzoxazole derivatives decorated with different alkylo/arylo amino groups dissolved in medium polar aprotic solvents: tetrahydrofuran and butyl chloride, exhibit dual fluorescence from the locally excited state (1LE) and a highly polar charge transfer (CT) state. Ambient-temperature time-resolved fluorescence investigations prove the bimodal kinetics of the excited-state electron transfer reaction 1LE→1CT. The lack of any CT emissions in cyclohexane and highly polar acetonitrile is presumably due to an efficient inter-system crossing process or fast deactivation of a low-lying CT state. In addition, strong CT properties inspired us to check a possibility to vary the absorption of the first UV–Vis maxima under influence of the external bicolour coherent laser light and the related optical second harmonic generation (SHG). The two coherent beams of the infrared Er:glass laser at 1540 nm/770 nm formed gratings in the photopolymer solidified chromophore. The performed experiments are compared with the theoretically calculated electronic parameters within the B3LYP DFT approach. The presented data open novel type of materials, allowing to operate its transparency using external IR laser light in the near IR spectral range. Graphical abstract Image 1 Highlights • Donor-acceptor based benzoxazoles are explored with respect to spectra and laser stimulated NLO. • The CT was supported by the strongly negative value of the Gibbs free energy. • Principal role is played by increasing twist angle between donor and acceptor planes. • variation of donor group LUMO level allow to operate by the second order susceptibilities. [ABSTRACT FROM AUTHOR]

Solid state solution AgGaGe 3(1–x) Si 3x Se 8 in the range of x = 005–030 were synthesized and absorbance, FTIR, Raman spectroscopy, second harmonic generation measurements has been performed to explore linear and non-linear optical features The measured SHG intensity demonstrate significant dependence of non-linear optical properties from silica content. Analysing of Urbach’s energy and Raman spectra allowed to determine the degree of defect depending on the chemical composition and temperature. [ABSTRACT FROM AUTHOR]

New quaternary sulfide PbGa 2 GeS 6 crystal was synthesized from co-melting high-purity elements The studies of second harmonic generation and the third harmonic generation for new quaternary sulfide PbGa 2 GeS 6 crystal have shown that its nonlinear optical response is higher with respect to other similar compounds. The band structure analysis performed by X-ray spectroscopy methods and first principles DFT band structure calculations indicate that the main contributions of the S 3p states are located at the top of valence band, while those of the Ga 4p states give contribution to the central and upper portions of the valence band of the PbGa 2 GeS 6 compound. The calculations reveal that the band gap E g  = 2.445 eV is indirect and is formed between the valence Γ-point and the conduction X-point of Brillouin zone. The theoretically evaluated band gap energy is close to the experimental value, namely E g  = 2.37 eV at 300 K The present results allow recommending PbGa 2 GeS 6 for nonlinear optical application in the near IR spectral range. At the same time, the crystal possesses a good transparency in the mid-IR spectral range. [ABSTRACT FROM AUTHOR]

Magnesium and Copper co-doped Zinc oxide nanorods (ZnO NRs) were grown on glass substrates applying hydrothermal technique. They were investigated with respect to their structural and morphological insights through X-ray diffraction (XRD) patterns, field emission scanning electron microscope (FESEM) and atomic force microscope (AFM) technique. The nanorod diameters were found to vary within 105 nm–153 nm. The nanorods were hexagonal in shape with wurtzite structure and oriented along c -axis. Band gap magnitudes were evaluated from the UV–Visible absorption spectra and were found to be higher for Mg5%Cu2%ZnO nanorod sample owing to its smaller crystallite size. Photo-polarization did the additional alignment in the nanorod samples to observe optical nonlinearity of the first and second order. When the spectral energy of the laser beam matched with the energy of the absorption band edge of the samples, we observed also third harmonic generation (THG) besides second harmonic generation (SHG). Quantum chemical calculation using norm-conserving pseudo-potential method was applied to confirm the origin of the effects. [ABSTRACT FROM AUTHOR]

We explore second harmonic generation (SHG) features of nanocrystalline SiC films based natural microcavities (MC) with resonance modes in the vicinity of the fundamental radiation at 1064 nm wavelength for nanocrystalline films of 24R, 27R polytypes characterized by high radiation doubling frequency coefficients. The natural walls of the SiC NC serve a role of cavities. To learn the nonlinear resonance features of the MC near the fundamental wavelength 1064 nm three series of the nc-SiC films indicated as 7495, 7517 and 7522 with thicknesses varying within 250–600 nm were fabricated. The role of the coherent and non-coherent contributions with taking into an account of cavity resonance modes is discussed. The giant increase of the SHG was achieved which may be used for further fabrication of the frequency transducers and nonlinear optical triggers. [ABSTRACT FROM AUTHOR]

We have performed the studies of photoinduced second harmonic generation in the ZnO nanorods doped by Thulium with different content (0.1; 0.2;0.5% of Tm). The illumination was performed with the Er:glass laser emitting at 1540 nm wavelength of the 10 ns laser and the output second harmonic generation (SHG) was studied. The AFM data analysis was performed. The role of the rare earth Tm ions on the morphology and the optically stimulated SHG is discussed. The SHG yield was found to be strongly dependent on Thulium content and Root Mean Square roughness of the studied layers. [ABSTRACT FROM AUTHOR]

We have shown that use of the Tl 3 PbCl 5 nanocrystallites leads to the occurrence of a substantial increase of the SHG induced by the coherent doubled frequency light. We have found that for the fundamental microsecond 10.6 μm wavelengths, there exists a possibility to increase the SHG during illumination at 5.3 μm wavelength. The detailed analysis of the IR induced SHG has shown that the nanocrysatalline interfaces play here the principal role. Another important factor is the contribution of the phonon subsystem due to the presence of the IR stimulated anharmonic phonons. These results are compared with those of bulk crystals. [ABSTRACT FROM AUTHOR]

Abstract: X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated (001) surfaces of AgCd2GaS4 and AgCd2GaSe4 single crystals grown, respectively, by the Bridgman method and the method of direct crystallization have been measured in the present work. The X-ray photoelectron spectroscopy (XPS) results reveal high chemical stability of (001) surfaces of AgCd2GaS4 and AgCd2GaSe4 single crystals. Electronic structure of AgCd2GaS4 has been calculated employing the full potential linearized augmented plane wave method. For the AgCd2GaS4 compound, the X-ray emission bands representing the energy distribution of the valence Ag d-, Cd d-, Ga p- and S p-like states were recorded and compared on a common energy scale with the XPS valence-band spectrum. The theoretical and experimental data regarding the occupation of the valence band of AgCd2GaS4 were found to be in excellent agreement to each other. Second harmonic generation (SHG) efficiency of AgCd2GaS4 by using the 320ns CO laser at 5.5μm has been recorded within the temperature range 80–300K. Substantial increase of the photoinduced SHG which in turn is substantially dependent on the temperature has been detected for the AgCd2GaS4 compound. [Copyright &y& Elsevier]

Abstract: In this paper, we report on novel Ag0.5Pb1.75GeS4 single crystals grown by the Bridgman–Stockbarger method. For these crystals we have performed X-ray photoelectron spectroscopy (XPS) studies of the valence-band and core-level electron states. Second harmonic generation efficiency of Ag0.5Pb1.75GeS4 powder samples by using CO2 laser light depending on the power density up to 1100MW/cm2 has been obtained within the temperature range 77–520K. The obtained dependences indicate relatively strong enhancement of photoinduced SHG output efficiencies as temperature increases. Both the spectra taken at ambient and 520K temperatures have shown similar behavior—rapid growth to saturated values of SHG efficiency with an increase of fundamental beam power density up to 400MW/cm2, then slowly decreasing with power density reaching a value of 800MW/cm2 and finally these features show a second small maximum at a fundamental beam power density equal to 900MW/cm2. Beyond this power density both SHG values start to decrease. [Copyright &y& Elsevier]

Complex temperature studies of optically stimulated second harmonic generation (SHG) at 1064 nm for pulsed 10 ns Nd:YAG laser radiation under illumination of two coherent laser beams (at 1064 nm and its 532 nm second harmonic) were carried out by means of the Maker fringe method. The bicolour coherent process allowed detection of some additionally induced non-centrosymmetry. The effect was studied at different temperatures and experimental geometries in YAB:Cr3+ single crystals. We found that Cr3+ ions play a principal role in the observed effects. The output of optically stimulated SHG was generally non-spherical in the sequence profile, contrary to the traditional non-stimulated SHG. Moreover, we also established that the optimal conditions for obtaining SHG corresponded to the fundamental/writing beam intensities ratio 6:1. A specially performed control of the photo-thermal sample heating showed that the increase of temperature did not exceed 1.2 K, which allowed the influence of photo-thermal heating to be neglected. The optimal input–output laser geometry corresponded to s-p polarisation and to the angle of about 32° between the photo-inducing and fundamental beams. Additionally in the studied temperature range (77–295 K) there was observed an enhancement of the output second-order susceptibilities from 0.72 pm/V up to 1.02 pm/V. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we report on the structural and optical properties of novel Ag0.98Cu0.02GaGe3Se8 single crystals that were synthesized by the Bridgman–Stockbarger technique. We have performed illumination by 10.6μm CO2 pulsed laser working in the microsecond time duration regime. Such illumination allows causing substantial changes for both pure electronic nonlinear optical effects like optical second harmonic generation as well as piezooptical effects described by the fourth rank tensors. The measurements of the piezo-optical effects were carried out at different temperatures. The effects are observed only during the IR CO2 laser illumination and are disappeared after switching off the illumination. Simultaneously the IR induced optical second harmonic generation at Er:glass laser fundamental wavelength 1540nm was performed during illumination by nanosecond Nd:YAG and Er3+:glass laser. The observed effects allow to use the studied materials as promising for IR-optoelectronic devices. [Copyright &y& Elsevier]

Because noncentrosymmetric [Sb7S8Br2](AlCl4)3single crystals possess a wide optical transparency region, it is a promising material for nonlinear optical applications. We have calculated the dispersion of linear and nonlinear optical susceptibilities including optical second harmonic generation (SHG) using a relaxed geometry. We find that the fundamental optical absorption edge situated at about 2.03 eV is in excellent agreement with the experimental data. Calculations of ε2xx(ω), ε2yy(ω), and ε2zz(ω) tensor components of the frequency-dependent dielectric function are presented. The single crystal possesses a considerable anisotropy of linear optical susceptibilities, which usually favors an enhanced phase matching conditions necessary to observe SHG and optical parametric oscillator (OPO) effects. Our calculations show that, in [Sb7S8Br2](AlCl4)3, |χ123(2)(ω)| is the principal tensor component having the highest value of SHG at zero frequency limit as well as at 1.165 eV (λ = 1064 nm) laser wavelength generation. The microscopic second-order hyperpolarizability, β123, of the dominant SHG component is calculated at the static limit and at λ = 1064 nm. [ABSTRACT FROM AUTHOR]

Abstract: We have performed firstly studies of the photoinduced second order susceptibilities in the Au nanoparticles (NP) A, B and C under simultaneous influence of the bicolor 1064nm and bicolor laser treatment (1064nm 10ns pulsed laser with pulse power densities 532nm 10ns laser treatment and the cw 300mW 532nm SHG coherent laser beams. We have studied three types of samples possessing irregular and different dense parameters of the Au NP deposited on the ITO substrate. We have found that the maximal bicolor (1064nm and 532nm) stimulated optical second harmonic generation for the 10ns pulse duration was observed for the samples possessing irregular Au NP deposited on the ITO. We have performed studies of the photoinduced second order susceptibilities in the Au NP under simultaneous influence of the bicolor 1064nm and bicolor laser treatment (1064nm 10ns pulsed laser with pulse power densities 532nm 10ns laser treatment and the cw 300mW 532nm SHG coherent laser beams). We have found that during the 15–20min of the cw treatment there occur the principal changes in the absorption maxima. These maxima indicate on the occurrence of the additional absorption nearby the 308nm and 310nm and 345nm spectral bands. The later are caused by the occurrence of the trapping levels in the border between the ITO substrate and the Au nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: The complex studies of photoinduced absorption, second harmonic generation and third harmonic generation were performed for TiO2 films of different morphology. In particular we have studied the influence of a bicolor laser beam treatment by a 300mW green cw laser emitting at 532nm on changes of absorption, birefringence and third harmonic generation on TiO2 films. We have performed the corresponding measurements using as a photoinducing light a glass erbium 10ns pulsed laser with a fundamental wavelength of about 1540nm together with its second harmonic generation (SHG) at 770nm using the method of bicolor laser treatment and a frequency repetition of about 10Hz. Varying the power density ratios between the fundamental and its SHG we have established the optimal conditions to achieve maximal photoinduced changes of absorption, birefringence and third harmonic generation (THG). We have detected changes of the birefringence and of the THG immediately after the laser treatment. We study an influence of the nanoparticle''s sizes on the observed changes of the optical features. Additionally we have studied the role of different chemical treatment on the structural and optical parameters. [Copyright &y& Elsevier]

Abstract: Optical treatment of Ca4NdO(BO3)3:Yb under continuous laser illumination at different wavelengths led to substantial changes of optical absorption and optical second harmonic generation. The treatment was performed successively by infrared (780nm), red (650nm), green (532nm) and blue (405nm) laser wavelengths with powers varying within the 200–400mW range. We demonstrated enhancement of the optical second harmonic generation in the Ca4NdO(BO3)3:Yb (1.9% in weighting unit) crystals under the influence of the green cw laser at 532nm. The principal changes were observed after 15min of the treatment. A correlation between the occurrence of the hyperfine structure in the absorption spectra and the enhancement of the optical second harmonic generation was found. The additional treatment by the blue laser led to disappearance of appeared photo-induced changes of absorption and decrease of the optical second harmonic generation. It is principal that the effect is non-reversible in time and it does not depend on the photo-inducing light polarization. The principal origin of the observed photo-induced optical second harmonic generation is photo-polarization of the particular rare earth localized levels and formation of the stable polarized states due to the presence of Yb ions, playing crucial role. No such effects were observed in pure Ca4NdO(BO3)3. [Copyright &y& Elsevier]

Abstract: During bicolor optical treatment by two coherent laser beams from 25ps Erbium-glass laser (λ =1.54μm), we have established substantial increase of effective optical second-order susceptibility near the critical temperature points corresponding to the glass structural transformation near 435°C. The increasing Er3+ content favors substantial increase of the photoinduced optical second harmonic generation (SHG). This temperature dependence of the second-order optical susceptibilities detected by the SHG correlates well with the differential scanning calorimetric (DSC) measurements. At the same time, the effect exists only in a narrow temperature range (up to 12°C) . There was not temperature hysteresis. Possible physical mechanisms of the phenomenon observed are discussed. [Copyright &y& Elsevier]

Abstract: We have evidenced the high sensitivity of infra red-induced second harmonic generation (IR-ISHG) to the structural changes that occurred in amorphous hydrogenated silicon films (a-Si:H) prepared by Rf-glow discharge technique at different substrate temperatures and doping types. In every case, a maximal signal of the IR-induced SHG is achieved at a temperature of about 110K and pump–probe delaying time about 22–38ps. This one indicates a marked effect of doped subsystems in the observed non-linear optical effects. A tremendous effect of doping is established from a drastic change of the IR-induced SHG behavior presenting an anomaly at about 400MW/cm2 for a pumping power with wavelength 3.7μm. A minimum of the SHG is observed in that case for standard non-doped films. Note here that the doping type does not markedly affect the behavior of the second-order non-linear optical susceptibility. The thermo-annealing leads to a slight decrease of the effective second-order susceptibilities. More drastic changes are observed with doped samples for the pump-probe delaying time from about 39 till 24ps. [Copyright &y& Elsevier]

Abstract: We show that BiB3O6 (BiBO) crystals, well known for their excellent second harmonic generation (SHG) properties, may also be of interest for third-order optical phenomena, particularly for two-photon absorption (TPA). Photoinduced TPA measurements were performed under illumination of excimer Xe–F laser (λ =217nm) as a photoinducing (pumping) beam. It created a thin surface layer (about 85nm) that was a source of the observed photoinduced TPA. Raman shifted Nd-YAG laser radiation (λ =1.9μm) as well as its second and fourth harmonics (λ =950 and λ =475nm, respectively) were used as fundamental (probing) beams of the TPA. The highest values of the TPA β coefficient were achieved for a polarization of the pumping light directed along crystallographic axis b. Quantum chemical simulations indicate on substantial contribution of UV-induced electron–phonon anharmonicity to the observed TPA. The obtained values of TPA coefficients indicate a possibility of using BiBO crystals as UV-operated optical limiters in a wide spectral range. [Copyright &y& Elsevier]

Abstract: Photo-induced second harmonic generation (SHG) and two-photon absorption (TPA) responses in the single crystals of neodymium containing compounds (NdGaO3, K5Nd(MoO4)4, α-RbNd(WO4)2, and NdAl3(BO3)4) were found. The temperature dependences of the SHG and TPA stimulated by bicolor laser treatment at 1320 nm and 660 nm were studied as well. We found that in nanocomposites consisting of a polymer matrix and nanocrystals of mentioned above neodymium compounds nonlinear optical effects are substantially stronger when more polarizable ions such as Rb and K are present. The maximal achieved value of the SHG for 1320 nm laser beam was equal to about 0.25 pm/V for the nanocomposite containing RbNd(WO4)2. The maximal value of the TPA under the same conditions of the photo-treatment was equal to about 1.6 cm/GW also in case of this nanocomposite. [Copyright &y& Elsevier]

Abstract: An influence of the cw laser treatment at 660nm (red), 532nm (green) and 405nm (blue) wavelengths on the absorption in l-alanine crystals was studied. We have established that increasing time of illumination for red laser wavelength leads to slight changes of absorption backgrounds without changes in the spectral features. The drastic changes are observed after illumination by green laser leading to occurrence of two clear and several less clear bands correlating well with increasing illumination time. Their intensities are only slightly dependent on time of optical treatment. The remaining part of the spectra demonstrates substantially less changes. Increasing optical SHG show clear correlation with the behavior of the red laser induced absorption. The effect demonstrates slow time decay. [Copyright &y& Elsevier]

Abstract: We have found that the Ca4NdO(BO3)3 single crystals doped by Yb3+ (5at.%) present promising materials for optical second harmonic generation and for the photoinduced effects. In particularly it is found that illumination by single pulsed Nd-YAG lasers with power about 1GW/cm2 causes substantial changes of the corresponding optical constants. The value of the efficient second order susceptibility is about 1.8pm/V at wavelength 1064nm. [Copyright &y& Elsevier]

Abstract: We have discovered an occurrence of optical second harmonic generation at 1064nm fundamental wavelength for the α-BaB2O4 (ABO) crystal illuminated by 7ns nanosecond nitrogen laser of 337nm. The effect is observed only during illumination and achieves the maximum SHG output after 15–20min of treatment. After switching off of the UV laser treatment the SHG decreases during about 5min. The maximum second order susceptibility achieved was equal to about 2.1pm/V at 1064nm after about 20min of UV laser treatment. The observed SHG is explained by local photothermal heating of the crystals and photo stimulated photothermal anisotropy that favors an occurrence non-centrosymmetry of the local charge density. An additional investigations of the low-power (cw) He–Ne laser light indicate the absence of additional light scattering, which unambiguously indicates an absence of any additional microcrystalline states including non-cenrosymmetrical β-BaB2O4 phases. Probably photostimulated enhancement of thermal expansion anisotropy the main reason for the observed non-centrosymmetry. [Copyright &y& Elsevier]

Abstract: The influence of surface morphology on the photo-induced optical second harmonic generation (SHG) is established for specific iron garnet films deposited on (111) and (100) planes of the Gd3Ga5O12 substrate, respectively. The anisotropy of the film surface is assigned to the substrate crystallographic plane used. It is shown that the decrease of the film''s mean grain size enhances the output SHG signal. The increase of the mean grain size from 30 nm up to the 46 nm leads to a decrease of the photo-induced SHG (up to 30%). This could be used for the contactless diagnostic of garnet films'' morphology. [Copyright &y& Elsevier]

In the present study, Mg-doped ZnO (MZO) nanofilms (NF) were grown by spray pyrolysis technique. X-ray diffraction (XRD) patterns have shown an intense peak oriented along (002) crystalline plane confirming crystalline origin of grown MZO films. Atomic force microscopy (AFM) data revealed that the average roughness decreased significantly upon Mg doping from 20.3 nm to 4.72 nm. Ambient temperature photoluminescence spectra accounted for four emission bands in the visible spectral region due to the presence of various intrinsic defect centres in the films. The non-linear absorption coefficient (β eff) were estimated by open aperture Z-scan technique and found to be in the order of 10−2 (cm/W) and indicates a positive absorption nonlinearity. Additionally, it was observed that incorporation of the metal Mg ions leads to a decay of the second harmonic generation (SHG) and to a non-regular increase of the third harmonic generation (THG). Image 1 • Large change in the crystallite size from 13.30 nm to 43.81 nm due to Mg doping. • Average surface roughness of ZnO nanostructures varied significantly with Mg doping. • Enhancement of PL intensity infers the radiative transitions in the films. • SHG shows decrement in signal intensity with addition of Mg and THG shows an enhancement. [ABSTRACT FROM AUTHOR]

The crystals of LiNH 4 SO 4 in β-modification are synthesized and the parameters of their crystalline unit cell are refined from XRPD spectra using Rietveld method. A refractive indices dispersions for mechanically free and uniaxially compressed crystals with pressures σ m = 0–150 bar (m = X , Y and Z) along three principal crystallographic directions have been explored within 300–800 nm spectral range by spectral method. The influence of uniaxial mechanical pressure on the refractive parameters of the crystal has been established. The combined piezo-optic coefficients of the β-LiNH 4 SO 4 versus wavelengths are found. The nonlinear optical phenomenon of the second harmonic generation (SHG) efficiencies is investigated for powdered samples using the modified Kurtz method at 1064 nm wavelength. The principal analysis of the dispersion allows to establish a new relation between the linear and nonlinear optical responses. Possible application of such crystals is discussed. [ABSTRACT FROM AUTHOR]

• THG and SHG signals show substantial changes in a different combination of Sn and S. • Raman phonon modes were identified to dominant "A" symmetry modes. • X-Ray diffraction reveals tetragonal crystal structure with (1 1 2) preferential growth orientation. We propose a low-cost approach for the synthesis of multifunctional CuSnS 3 (CTS) ternary compound thin film via spray pyrolysis technique. By varying Sn and S doping concentrations, a high energy absorber layers of CuSnS 3 thin films were deposited on a glass substrate at a substrate temperature of 405 °C. The prepared samples were analysed with respect to their optical, structural and electrical and nonlinear optical properties. X-Ray diffraction (XRD) analysis reveals that the films exhibit a tetragonal crystal structure with a preferential growth orientation along (1 1 2). The surface morphology of the films was explored by atomic force microscopy (AFM) in tapping mode configuration. Variation in the carrier charge density and electrical properties were observed for different Sn and S combination. The analysis of the Raman spectra indicates the presence of multiple phases apart from CuSnS 3. The obtained Raman spectra were assigned to phonon mode as per zone centre phonon representation of optical and acoustic modes and identified to dominant "A" symmetry modes. The maximal laser stimulated induced second harmonic generation (SHG) signal was observed for the CTS 3 film and the corresponding second order nonlinear optical susceptibility which was equal to about 0.89 pm/V at 1064 nm and the minimal SHG signal was found for the CTS 2 film (about 0.22 pm/V). This strategic improvement in SHG and third harmonic generation (THG) signal efficiency endorses the role of Sn and S in modulating second and third harmonic generations in CuSnS3 compound. [ABSTRACT FROM AUTHOR]

• Second and third harmonic generation were exhibited by F:SnO 2 thin films. • Enhancement of UV emission signifies the increased oxygen vacancy defect. • Upward shift of fermi level in the conduction band outcomes the broadening of Band gap. Laser stimulated second and third harmonic generation effects in Fluorine doped tin oxide (F:SnO 2) nanostructures versus the fluorine content is presented. The F:SnO 2 nanostructures have been fabricated at various fluorine doping concentrations by spray pyrolysis technique. The films exhibit polycrystalline nature with a preferential growth orientation along (1 1 0) diffraction plane as evident from x-ray diffraction studies. The optical transmittance of the F:SnO 2 films has increased from 68% to 80%. Photoluminescence studies revealed that strong violet emission peak corresponds to ∼400 nm and relatively weak red emission peak at about ∼675 nm was observed for all the F:SnO 2 films. Increase in theβ eff value upon fluorine incorporation supports the applicability of the deposited films in passive optical limiting applications. The principal origin of second harmonic generation signals (SHG) for this type of nanostructures is played by the space charge density acentricity due to the F doping. The enhanced second and third harmonic generation signals observed on F:SnO 2 nanostructures endorses the credibility of these materials in various nonlinear optical trigger device applications. [ABSTRACT FROM AUTHOR]