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.

Silica matrices doped with red laser dyes

Sol-gel SiO₂ matrices activated with laser dyes for the red spectral region DCM, LK678 and benzopyran derivatives LD1 and LD2 were synthesized. Pyridine was used to prevent bleaching of the dyes during the synthesis of the matrices. Studied were the spectral and luminescent characteristics of the laser dyes in SiO₂ matrices. Laser pumping of DCM and LK678 made it possible to obtain stimulated emission. The laser efficiency of LK678 dye in the matrix was 1.5 times as high as that of rhodamine 6G. The absence of lasing radiation of the benzopyran derivatives LD1 and LD2 in the synthesized matrices was explained

Fluorescence properties of dyes for 570-800 nm lasing region in sol-gel silica

The spectral-fluorescence characteristics of the dyes for 570-800 nm lasing region: Rh6G, DCM, LD678, and Rh800 were studied with the purpose to clarify an influence of intermolecular interactions in SiO₂ matrix on processes of the excitation energy decay of the laser dyes in S₁ state. Their quantum yields Qfl and decay times τfl of fluorescence, radiative kr and non-radiative knr rate constants for solvents and matrices were measured and calculated. It was shown for the dyes with small solvent effect (Rh6G, LD678) that incorporation of them into the matrix did not cause the appreciable changes of Qfl and τfl values. While for the dyes with strong solvent effect (DCM and Rh800) - SiO₂ matrix takes the stabilizing influence upon their molecules in S₁ state and as a result their non-radiative losses were diminished and quantum yield was increased

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