RESUMO
Monolayer transition metal dichalcogenides (TMDs) have emerged as promising materials to generate single-photon emitters (SPEs). While there are several previous reports in the literature about TMD-based SPEs, the precise nature of the excitonic states involved in them is still under debate. Here, we use magneto-optical techniques under in-plane and out-of-plane magnetic fields to investigate the nature of SPEs in WSe2 monolayers on glass substrates under different strain profiles. Our results reveal important changes on the exciton localization and, consequently, on the optical properties of SPEs. Remarkably, we observe an anomalous PL energy redshift with no significant changes of photoluminescence (PL) intensity under an in-plane magnetic field. We present a model to explain this redshift based on intervalley defect excitons under a parallel magnetic field. Overall, our results offer important insights into the nature of SPEs in TMDs, which are valuable for future applications in quantum technologies.
RESUMO
New glass compositions containing high concentrations of Tb3+ ions were developed aiming at the production of magneto-optical (MO) fibers. This work reports on the structural and MO properties of a new glass composition based on (100 - x)(41GeO2-25B2O3-4Al2O3-10Na2O-20BaO) - xTb4O7. Morphological analysis (HR-TEM) of the sample with the highest concentration of Tb3+ ions confirmed the homogeneous distribution of Tb3+ ions and the absence of nanoclusters. All the samples presented excellent thermal stability against crystallization (ΔT > 100 °C). An optical fiber was manufactured by a fiber drawing process. The UV-Vis spectra of the glasses showed Tb3+ electronic transitions and optical windows varying from 0.4 to 1.6 µm. The magneto-optical properties and the paramagnetic behaviors of the glasses were investigated using Faraday rotation experiments. The Verdet constant (VB) values were calculated at 500, 650, 880, 1050, 1330, and 1550 nm. The maximum VB values obtained at 650 and 1550 nm for the glass with x = 18 mol% were -128 and - 17.6 rad T-1 m-1, respectively. The VB values at 500 and 1550 nm for the optical fiber containing 8 mol% of Tb4O7 were - 110.2 and - 9.5 rad T-1 m-1, respectively, while the optical loss at around 880 nm was 6.4 dB m-1.
RESUMO
CdFe2O4 nanoparticles of around 3.9 nm were synthesized using the coprecipitation method and protected by a silica layer. The nanoparticles were mixed with a coacervate and transformed into phosphate glasses with 1, 4 and 8% in mass of nanoparticles by the melt-quenching method. TEM images confirm that the nanoparticles were successfully incorporated into the matrix without inducing crystallization. 31P NMR and Raman spectral analyses show that new P-O-Si bonds are formed in the glasses containing nanoparticles. The glass transition increases as a function of the nanoparticle content due to an increase in the connectivity of the phosphate glass chains. The UV-Vis spectra show bands at 415 and 520 nm assigned to Fe3+ ions and at 1025 nm, characteristic of Fe2+ ions, indicating that some of the nanoparticles dissolve during the melting process. The sample with 8% CdFe2O4 presents a paramagnetic behavior. The glasses obtained are transparent, non-hygroscopic and possess enormous thermal stability which is important for the production of optical devices.
RESUMO
In this work, we present a new photochromic tungstate based glass which have both absorption coefficient and refractive index modified under laser exposure. The photosensitive effect is superficial under ultraviolet (UV) irradiation but occurs in the entire volume of the glass under visible irradiation. The effect can be obtained in any specific point inside the volume using an infrared femtosecond laser. In addition, the photosensitive phenomenon can be erased by specific heat treatment. This glass can be useful to substitute actual data storage supports and is a promising material for 3-dimensional (3D) and holographic optical storage.