Search

Transparent glass-ceramics with a Li2O–Al2O3–SiO2 (LAS) system have been extensively utilized in optical systems in which thermal stability is of utmost importance. This study is aimed to develop thermal treatment routes that can effectively control the structure of transparent LAS glass-ceramics and tune its thermal expansion coefficient within a wide range for novel applications in photonics and integrated optics. The optimal conditions for the nucleation and crystallization of LAS glass were determined by means of differential scanning calorimetry and a polythermal analysis. XRD, Raman spectroscopy, and TEM microscopy were employed to examine the structural changes which occurred after heat treatments. It was found that the second stage of heat treatment promotes the formation of β-eucryptite-like solid solution nanocrystals, which enables effective control of the coefficient of thermal expansion of glass-ceramics in a wide temperature range of −120 to 500 °C. This work provides novel insights into structural rearrangement scenarios occurring in LAS glass, which are crucial for accurately predicting its crystallization behavior and ultimately achieving transparent glass-ceramics with desirable properties. [ABSTRACT FROM AUTHOR]

Atmospheric water adsorbed by porous materials may significantly change its electrodynamic response in a wide frequency range. Mechanical and chemical stabilities of silicon dioxide along with a proven manufacturing method of porous SiO2 samples made it convenient for studying the effects of moisture adsorption on various parameters of the porous media. We report the dielectric properties of SiO2-based nanoporous glass in the frequency range of 20 Hz–400 THz at ambient atmospheric conditions and at a low residual pressure of ≤1 mbar. We observed a significant low-frequency dispersion of the complex dielectric permittivity and enhancement of dielectric loss for the porous sample exposed to the ambient moisture. In the terahertz range, the change in dielectric response is smaller and correlates with the moisture saturation of the sample. [ABSTRACT FROM AUTHOR]

Space-selective laser-induced crystallization of glass enables direct femtosecond laser writing of crystal-in-glass channel waveguides having nearly single-crystal structure and consisting of functional phases with favorable nonlinear optical or electrooptical properties. They are regarded as promising components for novel integrated optical circuits. However, femtosecond-laser-written continuous crystalline tracks typically have an asymmetric and strongly elongated cross-section, which causes a multimode character of light guiding and substantial coupling losses. Here, we investigated the conditions of partial remelting of laser-written LaBGeO5 crystalline tracks in lanthanum borogermanate glass by the same femtosecond laser beam which had been used for their writing. Exposure to femtosecond laser pulses at 200 kHz repetition rate provided cumulative heating of the sample in the vicinity of the beam waist sufficient to provide space-selective melting of crystalline LaBGeO5. To form a smoother temperature field, the beam waist was moved along the helical or flat sinusoidal path along the track. The sinusoidal path was shown to be favorable for tailoring the improved cross-section of the crystalline lines by partial remelting. At optimized laser processing parameters, most of the track was vitrified, and the residual part of the crystalline cross-section had an aspect ratio of about 1:1. Thermal-induced stress emerging during the tailoring procedure was efficiently eliminated by fine post-annealing. The proposed technique suggests a new way to control the morphology of laser-written crystal-in-glass waveguides by tailoring their cross-section, which is expected to improve the mode structure of the guided light. [ABSTRACT FROM AUTHOR]

Featured Application: The investigated YAS glass microspheres doped with Nd3+ ions have great potential as remote optical temperature sensors. Moreover, they are suitable for the development of laser devices with low power thresholds. Yttria–alumina–silica (YAS) glass microspheres doped with Nd3+ ions were excited with a 532 nm continuous laser in order to study the dependency of the wavelength of the whispering gallery mode (WGM) peaks on the temperature of the sample. This was possible due to a previous calibration of the 808 nm and 890 nm emission bands of the Nd:YAS glass sample for different temperatures using the fluorescence intensity ratio (FIR) technique. A maximum sensitivity of 15 × 10−6 K−1 and a temperature resolution limit of 0.2 K were obtained for the microsphere sensor. Moreover, laser emission at 1064 nm was observed by continuous pumping at 532 nm, and a power threshold of 100 mW was determined. Upconversion emissions of Nd3+ were also studied by exciting the sample at 808 nm. [ABSTRACT FROM AUTHOR]

We present a novel strategy for the synthesis of pure and Eu-doped γ-Ga2O3 nanoparticles with an in situ organic capping resulting from a non-aqueous solution-based benzyl alcohol synthesis route. Photoluminescence spectroscopy highlights the concomitant benzoate-related and γ-Ga2O3 exciton-like Eu3+ excitations in the UV, and a blue emission superimposed onto γ-Ga2O3 donor-acceptor recombination, ascribable to organic moieties different from benzoate. [ABSTRACT FROM AUTHOR]