S. González-Pérez

Laser irradiation in Nd3+ doped strontium barium niobate glass

A local nanocrystalline formation in a neodymium doped strontium barium niobate (SBN) glass has been obtained under argon laser irradiation. The intense emission around 880 nm, originated from the F43/2 (F45/2) thermalized level when the glass structure changes to a glass ceramic structure due to the irradiation of the laser beam, has been studied. The intensities and lifetimes change from this level inside and outside the irradiated area made by the laser excitation. They have been analyzed and demonstrated that the desvitrification process has been successfully achieved. These results confirm that nanocrystals of SBN have been created by the laser action confirming that the transition from glass to glass ceramic has been completed. These results are in agreement with the emission properties of nanocrystals of the bulk glass ceramic sample. The present study also suggests that the SBN nanocrystal has a potential application as temperature detector.

Optical amplification in Er3+-doped transparent Ba2NaNb5O15 single crystal at 850 nm

Positive optical gain around 5 cm−1 (∼21 dB/cm) has been observed in Er3+-doped Ba2NaNb5O15 single crystal using a pump and probe experimental setup. High power laser pulses at 532 nm have been used as the pump source in order to strongly populate the S43/2(H211/2) levels of the Er3+ ions due to ground state absorption. Low signal beam cw laser radiation at 850 nm has been used as the probe beam to stimulate the emission associated with the S43/2(H211/2)→I413/2 electronic transition of the Er3+ ions. The process has been modelized as a four level system, and its population has been analyzed and simulated in order to study the gain dynamics. Optical amplification of the probe signal has been observed during the first 60 μs, which represents a good agreement between the measured lifetime of the S43/2(H211/2) levels and the reported simulation.

Control of the local devitrification on oxyfluoride glass doped with Er3+ ions under diode laser irradiation

Temperature control of the devitrification process in an erbium doped oxyfluoride glass under laser irradiation is reported. The green upconversion emissions around 525 and 545 nm originated from the thermalized H211/2 and S43/2 levels were studied when the glass structure changes to glass ceramic during irradiation with a laser beam. Power dependence of the fluorescence intensity ratio was used to determine the temperature of the irradiated zone. The transition from glass to glass ceramic takes place under 2300 mW of laser power with an estimated temperature around 783 K. This result agrees with the one obtained in the samples devitrified under conventional furnace treatment. Therefore, the estimation of the temperature of the irradiated zone through the fluorescence intensity ratio method allows a controlled devitrification. Moreover, an irradiated line has been written in the glass showing an important diffusion of the Pb2+ and F− ions. These results confirm that nanocrystals have been created due to t...

Pressure- and temperature-induced structural phase transitions in fluoride matrices monitoring by Eu3+ luminescence

The precipitation of micro-crystals identified as EuZrF7 has been induced by thermal treatment in the Eu3+-doped fluorozirconate glass. Moreover, using luminiscence of the Eu3+ ion, the experimental evidence of a reverse change has been obtained by a pressure-induced amorphization of the EuZrF7 polycrystal. There is a unique kind of site in the fluorozirconate glass, in which the different environments for the Eu3+ ions are generated by distortions of the EuZrF7 crystalline structure.

Optimizing the Deposition of Thin Layers of Organic-Inorganic Hybrid Perovskite Methylammonium Lead Iodide (CH3NH3PbI3) on Large Surfaces through Their Optical Properties

Nowadays, most of the Research and Development (R&D) efforts devoted to perovskite solar cells have been focused on achieving higher power conversion efficiencies, by using small sized substrates with even smaller active areas. The present paper proposes a method for optimizing the deposition of thin layers of organicinorganic hybrid perovskite methylammonium lead iodide (CH3NH3PbI3) on large surfaces (up to 75 mm x 75 mm) via spin coating procedures, performed in a clean room environment at room temperature and by considering their optical properties to assess their quality. Thus, in order to map the deposited area and realize studies about their optical properties, the absorption coefficient, the refractive index and layers thicknesses were determined by using a high accuracy spectroscopic ellipsometer system based on rotating compensator ellipsometer (RCE) technology from the J.A. Woolam Co. as functions of the wavelength, within a spectral range from 250 to 800 nm. Also, the samples were studied with a fluorescence spectroscopic system, in order to evaluate their photoluminescence properties and, in order to validate the chosen methodology; an Atomic Force Microscopy was used to verify the layers uniformity and thicknesses.