Person: Sotillo Buzarra, Belén
Universidad Complutense de Madrid
Faculty / Institute
Física de Materiales
Now showing 1 - 10 of 17
- PublicationSíntesis y caracterización de micro- y nanoestructuras de ZnS:X (X=Al, Ga, In)(Universidad Complutense de Madrid, 2015-03-03) Sotillo Buzarra, Belén; Fernández Sánchez, Paloma
- PublicationControl of waveguide properties by tuning femtosecond laser induced compositional changes(American Institute of Physics, 2014) Hoyo Muñoz, Jesús del; Martínez Vázquez, Rebeca; Sotillo Buzarra, Belén; Teddy Fernández, Toney; Siegel, Jan; Fernández Sánchez, Paloma; Osellame, Roberto; Solís Céspedes, Francisco JavierLocal compositional changes induced by high repetition rate fs-laser irradiation can be used to produce high performance optical waveguides in phosphate-based glasses. The waveguide refractive index contrast is determined by the local concentration of La, which can be changed by the action of the writing laser pulses. In this work, we have investigated the degree of control that can be exerted using this waveguide writing mechanism over the cross-section of the guiding region, and the local refractive index and compositional changes induced. These variables can be smoothly controlled via processing parameters using the slit shaping technique with moderate Numerical Aperture (NA 0.68) writing optics. The combined use of X-ray microanalysis and near field refractive index profilometry evidences a neat linear correlation between local La content and refractive index increase over a broad Δn interval (>3 x 10^2). This result further confirms the feasibility of generating efficient, integrated optics elements via spatially selective modification of the glass composition.
- PublicationCompetition effects during femtosecond laser induced element redistribution in Ba- and La-migration based laser written waveguides(MDPI AG, 2021-06) Macías Montero, Manuel; Moreno Zárate, Pedro; Muñoz, Francisco; Sotillo Buzarra, Belén; García Pardo, Marina; Serna, Rosalia; Fernández Sánchez, Paloma; Solís, JavierFs-laser induced element redistribution (FLIER) has been a subject of intensive research in recent years. Its application to various types of glasses has already resulted in the production of efficient optical waveguides, tappers, amplifiers and lasers. Most of the work reported on FLIER-based waveguides refers to structures produced by the cross-migration of alkali (Na, K) and lanthanides (mostly La). The latter elements act as refractive index carrying elements. Herein, we report the production of Ba-based, FLIER-waveguides in phosphate glass with an index contrast > 10^(-2). Phosphate glasses modified with the same amount of Na_2O and K_2O, and variable amounts of BaO and/or La_2O_3 were used to produce the FLIER-waveguides with Ba and or La acting as index carriers. Ba-only modified glasses show a waveguide writing threshold and light guiding performance comparable to that of La-based structures. However, mixed Ba-La glasses show a much higher element migration threshold, and much smaller compositionally modified regions. This behavior is consistent with a competition effect in the cross-migration of both elements (Ba and La) against the alkalis. Such an effect can be applied to inhibit undesired element redistribution effects in fs-laser processing applications in multicomponent glasses.
- PublicationCathodoluminescence of In doped ZnS nanostructures grown by vapor-solid method(Elsevier Science SA, 2013-06-25) Piqueras de Noriega, Javier; Sotillo Buzarra, Belén; Fernández Sánchez, PalomaVapor–solid (VS) growth method at temperatures in the range from 1000 °C to 1200 °C has been used to obtain In doped ZnS micro- and nanostructures. The morphologies of the synthesized structures depend strongly on the deposition temperature, consisting on nano- and microswords, nanoribbons and nanoplates, with a major presence of nanoplates and strongly hierarchical structures at the higher In contents. The degree of impurity incorporation and the influence of the dopant on the luminescence properties have been studied. While in pure ZnS the main deep level bands are peaked in the blue-green region, In doped samples show an orange-red emission.
- PublicationObtention and characterization of ferrous chloride FeCl_2•4H_2O from water pickling liquors(MDPI, 2021-09) Alcaraz, Lorena; Sotillo Buzarra, Belén; Marco, Jose F.; Alguacil, Francisco J.; Fernández Sánchez, Paloma; López, Félix A.As a hazardous waste, water pickling liquors must be properly treated. An alternative consists of promoting the formation of ferrous salts from this residue due to their higher ferrous content. Since FeCl_2•4H_2O is widely used in several applications, obtaining pure crystals of this material appears to be an interesting prospect. However, this compound has scarcely been investigated. In the present work, FeCl_2•4H_2O crystals were obtained from water pickling liquors. Their structural and morphological characteristics were investigated by X-ray diffraction, scanning electron microscopy as well as Mossbauer spectroscopy. In addition, the photoluminescence study of the obtained samples was also assessed. It was observed that after some aging time, the obtained crystals changed in colour from green to more yellowish. As such, the aged sample was also evaluated, and their structural characteristics were compared with the original crystals. Despite this, the obtained crystals exhibit a FeCl_2•4H_2O structure, which is not modified with the aging of the sample.
- PublicationFabrication and characterization of ZnO:CuO electronic composites for their application in sensing processes(Institute of Electrical and Electronics Engineers (IEEE), 2021-02-01) Ramos Ramos, D.J.; Sotillo Buzarra, Belén; Urbieta Quiroga, Ana Irene; Fernández Sánchez, PalomaSensing behaviour of samples belonging to the system ZnO:CuO has been investigated. Samples with different proportions of ZnO and CuO have been sintered and exposed to a reducing agent as ethanol (C_2H_5OH). All the samples have been characterized not only from the point of view of the sensing properties but also regarding morphology, composition, crystallinity and luminescent properties in order to correlate these properties to the sensing behaviour. Sensitivity, response times, recovery and stability have been measured under exposure to ethanol vapour in concentrations 800, 4700 and 16000 ppm. Sensing cycles have been performed at three different temperatures: 25, 50 and 100 degrees C.
- PublicationWaveguide tapers fabrication by femtosecond laser induced element redistribution in glass(Institute of Electrical and Electronics (IEEE), 2020-12-01) Macías Montero, Manuel; Dias, Antonio; Sotillo Buzarra, Belén; Moreno Zárate, Pedro; Ariza, Rocío; Fernández Sánchez, Paloma; Solís, JavierHere in we present the fabrication and performance of waveguide tapers produced by femtosecond laser induced element redistribution in modified phosphate glasses. More particularly, it is demonstrated that by controlling the scan velocity during the writing process it is possible to adequately tune both the size of the modified area and the refractive index contrast to produce waveguides that can cope with mode field diameters in the range of 7 mu m. In addition, we fabricated tapered structures through the induction of an acceleration in the laser scanning velocity, resulting in a device that can efficiently convert a wide range of mode fields. The fine control achieved over the index contrast in the range of 10^(-3) and 10^(-2) would allow the production of a wide variety of tapers that could potentially be used to couple numerous photonic devices.
- PublicationRole of the La/K Compositional Ratio in the Properties of Waveguides Written by Fs-Laser Induced Element Redistribution in Phosphate-Based Glasses(MDPI, 2020-03-11) Moreno-Zarate, Pedro; Muñoz, Francisco; Sotillo Buzarra, Belén; Macias-Montero, Manuel; Atienzar, Julia; Garcia-Pardo, Marina; Fernández Sánchez, Paloma; Serna, Rosalia; Solis, JavierThe local modification of the composition of glasses by high repetition femtosecond laser irradiation is an attractive method for producing photonic devices. Recently, the successful production of waveguides with a refractive index contrast (Δn) above 10−2 by fs-laser writing has been demonstrated in phosphate glasses containing La2O3 and K2O modifiers. This large index contrast has been related to a local enrichment in lanthanum in the light guiding region accompanied by a depletion in potassium. In this work, we have studied the influence of the initial glass composition on the performance of waveguides that are produced by fs-laser induced element redistribution (FLIER) in phosphate-based samples with different La and K concentrations. We have analyzed the contribution to the electronic polarizability of the different glass constituents based on refractive index measurements of the untreated samples, and used it to estimate the expected index contrast caused by the experimentally measured local compositional changes in laser written guiding structures. These estimated values have been compared to experimental ones that are derived from near field images of the guided modes with an excellent agreement. Therefore, we have developed a method to estimate before-hand the expected index contrast in fs-laser written waveguides via FLIER for a given glass composition. The obtained results stress the importance of considering the contribution to the polarizability of all the moving species when computing the expected refractive index changes that are caused by FLIER processes.
- PublicationPreferential Growth of ZnO Micro- and Nanostructure Assemblies on Fs-Laser-Induced Periodic Structures(MDPI, 2020-04-11) Sotillo Buzarra, Belén; Ariza García, Rocío; Siegel, Jan; Solis, Javier; Fernández Sánchez, PalomaIn this work, we demonstrate the use of laser-induced periodic surface structures (LIPSS) as templates for the selective growth of ordered micro- and nanostructures of ZnO. Different types of LIPSS were first produced in Si-(100) substrates including ablative low-frequency spatial (LSF) LIPSS, amorphous-crystalline (a–c) LIPSS, and black silicon structures. These laser-structured substrates were subsequently used for depositing ZnO using the vapor–solid (VS) method in order to analyze the formation of organized ZnO structures. We used scanning electron microscopy and micro-Raman spectroscopy to assess the morphological and structural characteristics of the ZnO micro/nano-assemblies obtained and to identify the characteristics of the laser-structured substrates inducing the preferential deposition of ZnO. The formation of aligned assemblies of micro- and nanocrystals of ZnO was successfully achieved on LSF-LIPSS and a–c LIPSS. These results point toward a feasible route for generating well aligned assemblies of semiconductor micro- and nanostructures of good quality by the VS method on substrates, where the effect of lattice mismatch is reduced by laser-induced local disorder and likely by a small increase of surface roughness.
- PublicationThermal growth and luminescence of wurtzite ZnS nanowires and nanoribbons(Elsevier Science B.V., 2012-06-01) Piqueras de Noriega, Javier; Sotillo Buzarra, Belén; Fernández Sánchez, PalomaZnS nanowires and nanoribbons have been obtained by the vapor–solid (VS) method. The morphology depends mainly on the deposition temperature; nanowires are grown at temperatures between 300 °C and 650 °C while the growth of nanoribbons takes place at deposition temperatures in the range 650 °C–900 °C. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies show that from cubic ZnS precursor hexagonal-phase nanostructures are obtained. Cathodoluminescence (CL) and photoluminescence (PL) measurements show a dominance of the native defects related emission compared to the near band edge emission, with marked differences between nanowires and nanoribbons.