Nonlinear optical response of the nematic liquid crystal doped with polymer-azo-dye complex under picosecond laser pulses excitation

The nonlinear optical (NLO) response of the heterosystem based on nematic liquid crystal (LC) with incorporated polymer-azo-dye complex (PADC) was studied within the self-action of picosecond laser pulses at 532 nm. It was shown the enhancement of the refractive NLO response efficiency up to 20 % at lower excitation level (0.5-20 MW/cm2) and up to 5 times at higher excitation level (20-600 MW/cm2) for the PADC doped LC versus the components response and conventional azo-dye doped LC. The manifestation of three photoinduced mechanisms was observed with the rise of the PADC concentration in LC matrix: 1) orientation of the PADC; 2) trans-cis-trans isomerization; 3) cooperative response/aggregation effect. Each mechanism defines the heterosystem NLO response at corresponding PADC concentration range. The proposed smart material is promising for photonic application due to NLO properties control with variation of the PADC concentration

Effect of the Ba/Sr ratio on the optical properties of phosphate laser glass

Nonlinear optical (NLO) approach was utilized for the laser phosphate glasses characterization, being prepared by the molar substitution of Ba2 for Sr⁰²⁺ at a fixed ratio of other components in a mixture of Ba₁₋-x₀/Srx₀-P₂O₅-Al₂O₃-B₂O₃-RE₂O₃ (RE : Nd, La). The optical characterization of the glasses was provided by optical and FTIR spectroscopy and elastic scattering indicatrices analyses. It was shown that an efficiency of the photoinduced absorption/bleaching depends on the substitution Ba²⁺-Sr²⁺ level x due to the self-action of pulsed and CW laser radiation at wavelength 1064 nm. The proposed technique can be applied for the oxygen stoichiometry diagnostics for laser phosphate glasses. For the x = 0.25 composition it was obtained UV-vis range absorption and elastic scattering reduction within the lowest efficiencies of the NLO absorptive response under pulsed and CW laser excitation at wavelength 1064 nm. Such optical properties improvement was achieved by both the substitution level choice modification and the purification of the initial reagents

Nonlinear optical response of the KDP single crystals with incorporated TiO₂ nanoparticles in visible range: effect of the nanoparticles concentration

Nonlinear optical response of KDP single crystals with incorporated TiO₂ nanoparticles (NPs) was studied within the self-action of picosecond laser pulses at 532 nm and second harmonic generation at 800 nm femtosecond laser pulses pump. The optical characterization of the composites KDP:TiO2 was provided by elastic scattering indicatrices analyzes at 1064 nm. It was shown the significant reduction of the elastic scattering and self-action effects efficiencies in TiO₂ NPs doped KDP single crystals cut from pyramidal growth sector. The effect was attributed to the reduction of the non-controlled impurities concentration in the KDP:TiO₂ due to the NPs incorporation. The enhancement of second harmonic generation efficiency at about 60 % for pyramidal and 35 % for prismatic growth sectors was observed in composite crystals versus the nominally pure KDP matrix within the femtosecond pulses excitation at 800 nm. The obtained results indicate high potential for utilization of the KDP:TiO₂ single crystals in light frequency conversion.

Nonlinear optical response of nanocomposites based on KDP single crystal with incorporated Al2O3*nH2O nanofibriles under CW and pulsed laser irradiation at 532nm

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Effect of L-arginine additive on the growth and physical properties of Potassium /subihydrogen Phosphate single crystals

Potassium dihydrogen phosphate (KDP) single crystals doped with L-arginine (L-arg) amino acid were grown from aqueous solutions onto a point seed using the temperature reduction method. The incorporation of L-arg molecules into the crystal was verified by means of ninhydrin reaction. Undoped and L-arginine doped KDP crystals were characterized by XRD method and structure perfection of the doped crystals was shown o correspond to the one of pure KDP. It was established that incorporation of L-g molecules into KDP crystal had an effect on the formation of additional bonds in the crystal structure, that manifested itself in the thermal properties of the doped crystals. Investigation of ε^/ε|| value which characterizes the dielectric permittivity anisotropy showed that it was minimal at 0.5-1.0 wt.% L-arg concentrations. In this case, the introduced L-arg seems to lead to creation of additional hydrogen bonds and disappearance of proton vacancies bound up with aliovalent impurities. Since the crystals contain different impurity defects, L-arg molecules are oriented in he lattice in a different way, depending on the type of the defects, and diminish the anisotropy. The present study testifies that the attenuation of the values of DC conductivity, dielectric permittivity and loss tangent at L-arg concentrations of 1 wt.% is probably related o the content decrease of the proton vacancies and the impurity-proton vacancy complexes dipoles, formed due to incorporation of the impurity ions into the crystal. The incorporation of L-arg molecules into the crystalline matrix results in an order of magnitude enhancement of he refractive nonlinear optical (NLO) response efficiency and its sign turn to self-focusing effect versus the self-defocusing obtained in the nominally pure KDP crystal. Similar kind of the NLO response efficiency rise in the KDP single crystals doped with TiO₂ nanoparticles. The phenomenon can produce the enhancement of the optical harmonics generation efficiency due to the laser radiation localization and improvement of phase matching conditions realization

Observation of a Very Massive Galaxy Cluster at z = 0.76 in the SRG/eROSITA All-Sky Survey

Abstract: The results of multiwavelength observations of the very massive galaxy cluster SRGe CL2305.2–2248 detected in X-rays during the first SRG/eROSITA all-sky survey are discussed. This galaxy cluster has also been detected previously in the millimeter band in the South Pole Telescope (SPT-CL J2305–2248) and Atacama Cosmology Telescope (ACT-CL J2305.1–2248) surveys through the observation of the Sunyaev–Zeldovich effect. The spectroscopic redshift has been measured at the 6-m BTA telescope, z=0.7573. In addition, deep photometric measurements of galaxies have been performed at the Russian–Turkish 1.5-m telescope (RTT-150). The mass of the cluster is estimated from the eROSITA data to be (Formula presented.). We show that this cluster is among several tens of the most massive clusters in the observable Universe and among only a few most massive galaxy clusters at z>0.6