Optical Materials Activated with CeO2:Ln3+ Nanoparticles

Silica glasses and siliceous powders activated with CeO2:Ln3+ (Ln ¹ Ce) nanoparticles were synthesized by the sol-gel method and their structural and spectral-luminescent properties were investigated. It is shown that the main features of the Ln3+ ions are a high relative intensity of magnetic dipole transitions and sufficiently effective sensitization of their luminescence with labile photoreduced (Ce4+)- ions by means of superexchange mechanism or/and by transfer of electron

Optical Materials Activated with CeO2:Ln3+ Nanoparticles

Silica glasses and siliceous powders activated with CeO2:Ln3+ (Ln ¹ Ce) nanoparticles were synthesized by the sol-gel method and their structural and spectral-luminescent properties were investigated. It is shown that the main features of the Ln3+ ions are a high relative intensity of magnetic dipole transitions and sufficiently effective sensitization of their luminescence with labile photoreduced (Ce4+)- ions by means of superexchange mechanism or/and by transfer of electron

Functional birefringent elements imprinted by femtosecond laser nanostructuring of multi-component glass

A decade ago, a new type of self-organization process was observed in the bulk of SiO2 glass after irradiation with ultrashort laser pulses [1]. Under certain irradiation conditions, highly ordered nanostructures with features smaller than 20 nm could be formed in the irradiated volume. The sub-wavelength arrangement of these structures results in form birefringence, which was recently exploited for demonstrating a variety of functional optical elements in silica glass [2]. Despite excellent physical and chemical properties of fused silica, the applications of this glass are limited due to the expensive manufacturing process associated with high melting temperature. Recently the evidence of laser-induced nanogratings in glasses other than SiO2 was reported, including GeO2 glass [3], binary titanium silicate glass (ULE, Corning) and multicomponent borosilicate glass (Borofloat 33, Schott) [4]. However, birefringence induced in borosilicate glass was more than one order of magnitude lower than in pure SiO2 glass

Direct writing of birefringent elements by ultrafast laser nanostructuring in multicomponent glass

Self-assembled nanostructures created by femtosecond laserirradiation are demonstrated in alkali-free aluminoborosilicate glass. The growth of the induced retardance associated with the nanograting formation is three orders of magnitude slower than in silicaglass and is observed only within a narrow range of pulse energies. However, the strength of retardance asymptotically approaches the value typically measured in pure silicaglass, which is attractive for practical applications. A similar intensity threshold for nanograting formation of about 1 TW/cm2 is observed for all glasses studied. The radially polarized vortex beam micro-converter designed as a space-variant quarter-wave retarder for the near-infrared spectral range is imprinted in commercial Schott AF32 glass

Crystallization Behaviour and Nanostructuringin Alkali Niobiosilicate Glasses

23K2O-27Nb2O5-50SiO2 (KNS), 13K2O-10Na2O-27Nb2O5-50SiO2 (KNaNS) and 15K2O-12Li2O-27Nb2O5-46SiO2 (KLiNS) transparent glasses were synthesized by melt-quenching technique, and studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) to reveal the effect of the devitrification behaviour on transparent nanostructure. Just above the glass transition temperature Tg in the KNS glass, an unidentified phase was formed, while in KNaNS and KLiNS, mixed-alkali niobate phases with tungsten bronze structure were obtained by bulk crystallization. Heat treatments at Tg performed on the KNS glass resulted in the transparent nanostructure with second order harmonic generation (SHG) activity. Heat treatment for 10 h on KNaNS and KLiNS decreased the first DTA exothermic peaks (at least 24°C), indicating the bulk nucleation, which was confirmed by the DTA in comparison with the powdered as-quenched samples. KNaNS and KLiNS showed similar XRD profiles as the K3Li2Nb5O15 crystal with the five most intense peaks at 22.7, 29.4, 32.3, 46.3 and 52.0 deg. HRTEM micro- graph showed clear-cut nano-sized circular domains and spherical nanocrystals dispersed into the amorphous matrix

Structure of low-silica glasses in the K2O-Nb2O5-SiO2 system

The nanostructure and nonlinear optical properties of high-niobium glasses in the (1 − x)KNbO3-xSiO2 system with an SiO2 content x = 0.05-0.35 have been studied by small-angle neutron scattering (SANS), electron microscopy (EM), and second-optical-harmonic generation (SHG). Vitreous samples are manufactured by the methods of fast melt cooling (pressing with metal plates and quenching between rotating rolls). Glasses with x 0.2 are homogeneous, but form a silica-enriched nanostructure after thermal treatments. At temperatures below ∼T g + 50°C, silica-enriched regions manifest a very slight tendency to grow, whereas, according to SANS and X-ray diffraction data, their chemical composition is observed to shift appreciably towards SiO2 with thermal treatment. The obtained data on an inhomogeneous structure allows us to clarify the complicated character of the previously revealed dependence T g (x). Nano-inhomogeneous transparent samples produce a weak SHG signal, which indicates the quasi-periodic modulation of the chemical composition and, correspondingly, polarizability, in the volume of glass. The nonlinear optical phase KNbO3 precipitates at later stages of crystallization, when a glass loses its transparency. In this case, the SHG signal is amplified by several orders of magnitude