Optical second harmonic generation in CsLiB6O10 nanocrystallites incorporated to the olygoether photopolymer matrices induced by acustical field

Optical second harmonic generation in CsLiB₆O₁₀ (CLBO) large-sized nanocrystallites (15–40 nm) incorporated into the olygoether photopolymer matrices has been found at liquid helium temperature (LHeT). The second harmonic generation (SHG) has been measured for the source wavelength of the YAG : Nd laser ( = 1.06 m). Increasing acoustical power (up to 18.1 W/cm²) and acoustical frequencies at 14 kHz give maximal values of the output SHG. The measured SHG ₂₂₂ tensor component was comparable with the one for the traditional nonlinear optical crystals such as KH₂PO₄, KTiOPO₄, LiNbO₃. With decreasing temperature below 28 K the acoustically induced SHG signal strongly increases. A correlation between the acoustically induced SHG and low-frequency Raman modes has been found. The maximal acoustically induced SHG has been observed for the nanocrystallite concentration about 3.1% (in weighting units) and the crystallite sizes lying within the 35–40 nm. The SHG tensor coefficients were higher than for the proper CLBO crystals at least on the 13%. Advantageous and drawbacks of the presented model are discussed. The theory of the observed phenomena is explained on the ground of ab initio band energy calculations with taking into account of anharmonic electron-phonon interactions.     

Photoinduced nonlinear optical phenomena in Sb2Se3-BaCl2-SnCl2 glasses

Photoinduced nonlinear optical phenomena have been studied in amorphous Sb₂Te₃-CaCl₂-SnCl₂ glasses using photoinduced optical second harmonic generation (SHG). The photoinduced SHG signal was measured for double frequency of a CO₂ laser ( = 5.3 m) using a photoinducing CO laser ( = 5.5 m). We have found that the SHG signal intensity increases with increase of the CO laser photoinducing exposure and achieves its maximum value after 1.5 h. Absolute values of the SHG signals were more than one order in magnitude smaller comparing to a ₂₂₂ tensor component for the ZnSe single crystals. The SHG signal strongly increases if temperature decreases from 39 to 16 K. Femtosecond probe-pump measurements indicate existence of the SHG maximum at pump-probe time delay of about 43 ps. It is suggested that Sb-Se tetrahedra play a key role in the observed photoinduced nonlinear optical effects. Degree of noncentrosymmetry of corresponding bonds depends on time of the CO-laser illumination, temperature and mechanical stresses. Simultaneously, the investigated glasses can serve as promising materials for a femtosecond IR quantum electronics.     

Second-order optical effects in seed-mediated grown palladium nanoparticles

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.     

Quantitative Polarization-Resolved Second-Harmonic-Generation Microscopy of Glycine Microneedles

Second-harmonic generation (SHG) is a nonlinear optical process that can provide disease diagnosis through characterization of biological building blocks such as amino acids, peptides, and proteins. The second-order nonlinear susceptibility tensor χ⁽²⁾ of a material characterizes its tendency to cause SHG. Here, a method for finding the χ⁽²⁾ elements from polarization-resolved SHG microscopy in transmission mode is presented. The quantitative framework and analytical approach that corrects for micrometer-scale morphology and birefringence enable the determination and comparison of the SHG susceptibility tensors of β- and γ-phase glycine microneedles. The maximum nonlinear susceptibility coefficients are d₃₃ = 15 pm V⁻¹ for the β and d₃₃ = 5.9 pm V⁻¹ for the γ phase. The results demonstrate glycine as a useful biocompatible nonlinear material. This combination of the analytical model and polarization-resolved SHG transmission microscopy is broadly applicable for quantitative SHG material characterization and diagnostic imaging.     

Optical properties of zinc–vanadium glasses doped with samarium trioxide

Zinc–vanadium glasses doped with samarium oxide having the chemical composition Sm₂O_3(x) ZnO_(40?x) V₂O₅₍₆₀₎(where x = 0?1–0?5 mol%) were prepared by melt quenching method. The density of these glasses was measured by Archimedes method; the corresponding molar volumes have also been calculated. The values of density range from 3?7512 to 5?0535 gm/cm³ and those of molar volume range from 28?3004 to 37?6415 cm^?3. The optical absorbance studies were carried out on these glasses to measure their energy bandgaps. The absorption spectra of these glasses were recorded in UV–Visible region. No sharp edges were found in the optical spectra, which verify the amorphous nature of these glasses. The calculated optical bandgap energies of these glasses were found to be in the range of 0?3173–0?6640 eV. The refractive index and polarizability of oxide ion have been calculated by using Lorentz–Lorentz relations. The values of refractive index range from 1?1762 to 1?2901 and those of polarizability of oxide ion range from 1?6906 × 10^?24 to 2?2379 × 10 ^?24cm³.     

Second harmonic generation in surface crystallized 30GeS2 · 35Ga2S3 · 35AgCl chalcohalide glasses

The infrared transmitting surface crystallized chalcohalide glasses containing nontoxic and excellent nonlinear optical AgGaGeS₄ crystallites were fabricated by heat-treatment of the as-prepared 30GeS₂ · 35Ga₂S₃ · 35AgCl chalcohalide glass at 350 °C (T_g −10 °C) for 24 h. An intensive second harmonic generation (SHG) was observed clearly using the Maker fringe technique, and the origin of SHG was mainly ascribed to the AgGaGeS4 nonlinear optical crystallites contained in the surface crystallized layer. The thickness of the surface crystallized layer showing SHG activation is approximate 50 μm. The χ⁽²⁾ susceptibility of the prepared surface crystallized 30GeS₂ · 35Ga₂S₃ · 35AgCl chalcohalide glass is calculated to be about 12.4 pm/V at a fundamental wavelength of 1064 nm, which indicates a promising nonlinear optical material in the infrared spectral region.     

Phase-matched Optical Second-harmonic Generation in the Organic Crystal MBA-NP, (−)2-(α-methylbenzylamino)-5-nitropyridine

Abstract

Large (5 × 3 × 3 cm³) crystals of the organic nonlinear optical material MBA-NP have been prepared by growth from solution, in an optically and structurally highly perfect state. Oriented cut and polished specimens were examined by the Maker fringe technique at a wavelength of 1·064 µm. Analysis of the data yielded d ₂₂ as 69 × d₁₁ quartz with a corresponding coherence length of 2 µm. A large rotation of the X and Z dielectric axes with wavelength (30° over 200 nm) was observed. Type I phase-matched second-harmonic generation (SHG) was recorded. For the 1·064 µm dielectric axis set and a (010) faced crystal, phase matched SHG was observed for rotation about X to an angle of incidence of 45°. This angle is very sensitive to the correct alignment of dielectric axes and the effect of its misalignment was investigated.     

Magnetic susceptibility measurement of single iron/cobalt carbonyl microcrystal by atmospheric magnetophoresis

Abstract

In this study, the use of an innovative atmospheric magnetophoresis, which enables us to measure the mass magnetic susceptibility and mass of a microparticle simultaneously, was demonstrated. Using this technique, we determined the magnetic susceptibility of a crystalline deposit of iron/cobalt carbonyl, mainly composed of Fe₂(CO)₉, which was prepared photochemically from a gaseous mixture of iron pentacarbonyl (Fe(CO)₅) and cobalt tricarbonyl nitrosyl (Co(CO)₃NO). The mass magnetic susceptibility and the characteristic relaxation time of the microcrystal were (7.0±1.9)×10^?9 m³ kg^?1 and (5.6±2.2)×10^?4 s, respectively. The observed magnetic susceptibility shows that the microparticle was paramagnetic. Assuming that the density was equal to that of Fe₂(CO)₉ (2.1×10³ kg m^?3) and that the shape of the particle was spherical, a hydrodynamic radius of 4.7 μm and a mass of 0.91 ng were observed. It was suggested that Co was incorporated in Fe₂(CO)₉.     

A study on the <Emphasis Type="SmallCaps">l</Emphasis>-lysine-iodic acid: semi organic non linear optical single crystals for electro-optic applications

Non linear optical single crystals of l-lysine-iodic acid (LLI) of dimensions upto 24?×?14?×?5 mm³ have been grown successfully by slow evaporation technique from aqueous solution. The crystal structure of the grown material was solved by single crystal X-ray diffraction analysis and it was found that the LLI crystal belongs to monocinic system with space group P2₁. Functional groups of the grown crystal were identified by Fourier Transform Infrared (FTIR) spectral analysis. The UV–Vis spectral analysis was carried out to measure the transparent range of the LLI crystal which is nearly 85% and the band gap energy is found to be 5.51 eV. Thermal stability and decomposition temperature of LLI crystal was found by means of TGA and DTA analyses. The mechanical behavior of the grown crystal has been employed using Vicker’s micro hardness technique. The Second Harmonic Generation (SHG) efficiency of the crystal was investigated and it was found to be 3.2 times of KDP. The particle size dependent SHG studies of LLI crystals were performed using Nd:YAG laser. The laser damage threshold value of LLI crystal is found to be 8.54 GW/cm². Dielectric study indicates the reasonable dielectric constant and low dielectric loss of LLI crystal which are essential properties to develop optoelectronic devices. The ac and dc electrical conductivity measurements were carried out at various temperatures. Photoconductivity study exhibits the negative photoconductivity nature of the LLI crystal and the results are discussed for the first time.     

Magnetic Properties of Some Tellurite Glasses

The AC magnetic susceptibility in the range 5–130 K of the tellurite glass systems: TeO₂–MnO₂–ZnO–PbO and TeO₂–MnO₂–V₂O₅–Fe₂O₃ was measured and analyzed. The investigations of the AC magnetic susceptibility facilitated the determination of the molar susceptibility, paramagnetic magnetic susceptibility, paramagnetic Curie temperature, and magnetic entropy changes of the tellurite glasses. The results clarified that the temperature dependence of the magnetic susceptibility deviated from the Curie law and the increase of the small negative values of Curie temperature indicated negative interchange interactions between the antiferromagnetically coupled manganese ions within the present glass network. The magnetic moments evaluated from susceptibility measurements of the glasses show the predominance of the Mn²⁺ valence state than Mn³⁺ valence state of MnO₂.     

Fast-response p-i-n photodiodes for 0.9–2.4 μm wavelength range

Fast-response, uncooled p-i-n photodiodes with a long-wavelength spectral sensitivity boundary at λ = 2.4 μm have been created on the basis of GaSb/GaInAsSb/GaAlAsSb heterostructures. A low doping level (10¹⁴–10¹⁵ cm^?3) in the active layer ensured a low capacitance of the photodiode structure (below 1 pF at a sensitive area diameter of 100 μm) and a record small response time (on a level of 100–150 ps). The photodiode pass band reaches up to 2 GHz. The proposed devices are characterized by a small dark current level (500–1000 nA at a reverse bias voltage of 1–3 V) and a detection ability reaching 9 × 10¹⁰ cm Hz^1/2 W^?1 in a spectral interval of maximum sensitivity within 1.9–2.2 μm.     

Direct Measurements of the Strong Refractive Nonlinearity of Impurity Origin in Heavily-doped GaAs

Abstract

A strong dispersive nonlinearity below the band gap in heavily doped bulk n-GaAs is observed for differnet donor impurities. Negative refractive index changes of up to ?5 × 10^?3 are obtained in the spectral range 880–900 nm, induced by light of the same wavelength at an incident intensity of about 5 × 10⁵ W cm^?2. Since the lifetime of the nonlinearity is ～ 10^?10 s, it is suggested that a bistable device exploiting this effect could be constructed with a switching energy of (1?5) × 10^?14 J μm^?2.     

Morphological and kinetic aspects of thermal oxidation of SiC whisker reinforced Al203

Abstract

The thermal oxidation susceptibility of a 30 vol.-%SiC whisker reinforced Al₂0₃ composite in air at 1300–1500°C has been investigated. It was found that the morphological changes associated with scale evolution lead to the formation of mullite and a glassy phase. In particular, the scale cross-section consisted of a porous external scale (white), and an internal black layer in contact with the unreacted matrix. The black scale region was relatively thin (0–6 μm), and contained partially oxidized SiC whiskers as well as glassy phases. In some .instances, the inner black scale/matrix interface exhibited intergranular cracking. The presence of these cracks was attributed to internal stresses induced by volume increases associated with the oxidation reaction. Additionally, the rates of scale thickening and of weight gain exhibited parabolic behaviour. At 1500°C parabolic rate constants K_p and K_m of 1·18 × 10^?14 m² S^?1 and 2·23 × 10^?9 kg² m^?4 S^?1, respectively werefound. From the rate constant data, activation energies of 577 and 542 kJ mol^?1 were determined on the basis of scale thickness and weight gain, respectively. Apparently, the oxidation rates in the black subzone were somewhat high to be rate limiting. Hence, the exhibited activation energies were ascribed to the diffusion of oxidant across the white scale region.

MST/2013     

Synthesis,physical, ultrasonic waves,mechanical, FTIR,and dielectric characteristics of B2O3/Li2O/ZnO glasses doped with Y3+ ions

Six specimens of glasses with formula (70???x)B₂O₃/15Li₂O/15ZnO/xY₂O₃: x?=?0.0, 0.5, 1.0, 1.5, 2.0, and 2.5 mol%) have been synthesized via a conventional melt quenching technique. The produced specimens were named as BLZY0.0–BLZY2.5 according to x values. The physical, ultrasonic longitudinal (V_L) and shear (V_S) velocities, FTIR, and dielectric (50 Hz to 5 MHz) characteristics of the prepared glasses have been examined. With increasing content of Y₂O₃ from 0.0 to 2.5 mol%, the density (ρ) of the system increases linearly from 2512?±?11 to 2695?±?14 kg/m³, while the molar volume (V_M) decreases linearly from 2.6?±?0.011 to 2.57?±?0.013?×?10^?5 m³/mol. The oxygen packing density (OPD) as a number of the oxygen per unit composition in the glass sample is describing the packing tightness of the oxide network and thoroughly the compactness of the glass matrix. Values of the average boron–boron separation (d_B–B) decrease from 4.162 to 4.035?×?10^?10 (m) with 0 to 2.5 mol% Y₂O₃. Increasing formation of Y³⁺ ionic bonds with [BO_4/2]^1? may have an effect of lowering bond strength of B–O and thus shifting the absorption IR peak position. By increasing Y₂O₃ content in the investigated samples, the (V_L) and (V_S) increase linearly for the full-studied compositional range. The increasing number of strengthened bonds due to change coordination of B ions from 3 to 4 due to the increasing field strength of inserted accumulated Y³⁺ ions has the incentive impact to higher mechanical properties. The dielectric constant was decreased for Y₂O₃ content up to 1.5 mol% referring to cross-linkage formation with other elements, while the reduction in porosity at high content of Y₂O₃ is the main responsible for gradual enhancement in dielectric constant.

     

CMOS photodetector systems for low-level light applications

Electron beam induced second harmonic generation (SHG) is studied in Er³⁺ doped PbO–GeO₂ glasses containing silver nanoparticles with concentrations that are controlled by the heat-treatment of the samples. The SHG is observed at T = 4.2 K using a p-polarized laser beam at 1064 nm. Enhancement of the SHG is observed in the samples that are submitted to electron beam incidence. The highest value of the nonlinear susceptibility, 2.08 pm/V, is achieved for the sample heat-treated during 72 h and submitted to an electron beam current of 15 nA. The samples that were not exposed to the electron beam present a susceptibility of ≈0.5 pm/V.     

Nonlinear Optical Sulfides LiMGa8S14 (M = Rb/Ba,Cs/Ba) Created by Li+ Driven 2D Centrosymmetric to 3D Noncentrosymmetric Transformation

Cations that can regulate the configuration of anion group are greatly important but regularly unheeded. Herein, the structural transformation from 2D CS to 3D noncentrosymmetric (NCS, which is the prerequisite for second-order NLO effect) is rationally designed to newly afford two sulfides LiMGa₈S₁₄ (M = Rb/Ba, 1 ; Cs/Ba, 2 ) by introducing the smallest alkali metal Li⁺ cation into the interlamination of 2D centrosymmetric (CS) RbGaS₂. The unusual frameworks of 1 and 2 are constructed from C₂-type [Ga₄S₁₁] supertetrahedrons in a highly parallel arrangement. 1 and 2 display distinguished NLO performances, including strong phase-matchable second-harmonic generation (SHG) intensities (0.8 and 0.9 × AgGaS₂ at 1910 nm), wide optical band gaps (3.24 and 3.32 eV), and low coefficient of thermal expansion for favorable laser-induced damage thresholds (LIDTs, 4.7, and 7.6 × AgGaS₂ at 1064 nm), which fulfill the criteria of superior NLO candidates (SHG intensity >0.5 × AGS and band gap >3.0 eV). Remarkably, 1 and 2 melt congruently at 873.8 and 870.5 °C, respectively, which endows them with the potential of growing bulk crystals by the Bridgeman-Stockbarge method. This investigated system provides a new avenue for the structural evolution from layered CS to 3D NCS of NLO materials.     

Synthesis,structural, thermal and optical properties of TeO2–Bi2O3–GeO2–Li2O glasses

In this study, synthesis and characterization of novel quaternary tellurite glass system TeO₂–Bi₂O₃–GeO₂–Li₂O is presented. The compositions include TeO₂ and GeO₂ as glass formers while different proportion of Bi₂O₃ and Li₂O act as network modifiers. Differential thermal analysis, X-ray diffraction, scanning electron microscopy energy dispersive X-ray spectroscopy, laser ablation inductively coupled plasma mass spectrometry, UV–Vis and Raman spectroscopy are applied to study the structural, thermal and optical properties of the studied glasses. Obtained glasses possess a relatively low glass transition temperature (around 300 °C) if compared to other tellurite glasses, show good thermal transparency in the visible and near infra-red (from 2.4 to 0.4 μm) and can double the frequency of laser light from its original wavelength of 1064 nm to its second-harmonic at 532 nm (i.e. second harmonic generation).     

Thermal and photoluminescence properties of Er2S3-doped (As2Se3)90(GaSe)5Ge5 glasses

Thermal and photoluminescence characteristics of (As₂Se₃)₉₀(GaSe)₅Ge₅ glasses doped with different amounts of Er₂S₃ (Er amount from 0.1 to 3 at %) have been studied. Temperature-modulated differential scanning calorimetry measurements were used to study the glass transformation and thermal stability of these glasses. A 980-nm laser diode was used to pump the Er³⁺-doped glass samples, inducing a 1550-nm photoluminescence output signal. By appropriately pulsing the excitation, we measured the photoluminescence lifetime of the Er³⁺ state in these chalcogenide glasses.     

Use of the F − 2 : LiF Colour-centre Laser in Intracavity Laser Spectroscopy

Investigations of the F ^? ₂: LiF colour-centre laser used in intracavity laser (ICL) spectroscopy are reported. A F^? ₂: LiF laser operated at room temperature with a 200 μs pulse duration and 50–200cm^-1 pulse spectral width was used to form to basis of an ICL spectrometer with a threshold absorption sensitivity of 5 × 10 ^-8 cm ^-1 and a spectral resolution of 0·;041 cm^-1. The high sensitivity of the spectrometer enabled the recording in the 8000–9100cm ^-1 region of a variety of previously unrecorded lines of the v ₂ + 2v ₃ band of HDO and the v ₃ band of ¹² CH ₄ and ¹³ CH ₄. The special method for describing the hole enhancement in the laser radiation spectrum due to the absorption lines was used for measuring the half-widths and relative intensities of the H₂O lines.     

Structural relaxation and electrical conductivity of molybdovanadate glass

⁵⁷Fe Mössbauer spectrum of conductive barium iron vanadate glass with a composition of 20BaO·10Fe₂O₃·70V₂O₅ (in mol%) showed paramagnetic doublet peak due to distorted Fe^IIIO₄ tetrahedra with isomer shift (δ) value of 0.37 (±?0.01) mm s^?1. Mössbauer spectra of 20BaO·10Fe₂O₃·xMoO₃·(70???x)V₂O₅ glasses (x?=?20–50) showed paramagnetic doublet peaks due to distorted Fe^IIIO₆ octahedra with δ’s of 0.40–0.41 (±?0.01) mm s^?1. These results evidently show a composition-dependent change of the 3D-skeleton structure from “vanadate glass” phase, composed of distorted VO₄ tetrahedra and VO₅ pyramids, to “molybdate glass” composed of distorted MoO₆ octahedra. After isothermal annealing at 500 °C for 60 min, Mössbauer spectra also showed a marked decrease in the quadrupole splitting (Δ) of Fe^III from 0.70 to 0.77 to 0.58–0.62 (±?0.02) mm s^?1, which proved “structural relaxation” of distorted VO₄ tetrahedra which were randomly connected to FeO₄, VO₅, MoO₆, FeO₆ and MoO₄ units by sharing corner oxygen atoms or edges. DC-conductivity (σ) of barium iron vanadate glass (x?=?0) measured at room temperature was 3.2?×?10^?6 S cm^?1, which increased to 3.4?×?10^?1 S cm^?1 after the annealing at 500 °C for 60 min. The σ’s of as-cast molybdovanadate glasses with x’s of 20–50 were ca. 1.1?×?10^?7 or 1.2?×?10^?7S cm^?1, which increased to 2.1?×?10^?2 (x?=?20), 6.7?×?10^?3 (x?=?35) and 1.9?×?10^?4 S cm^?1 (x?=?50) after the annealing at 500 °C for 60 min. It was concluded that the structural relaxation of distorted VO₄ tetrahedra was directly related to the marked increase in the σ, as generally observed in several vanadate glasses.