Papers by Sara García-Revilla
NATO science for peace and security series, Sep 21, 2012
Proceedings of SPIE, Mar 10, 2015
The present investigation explores the upconversion properties of Er3+- doped La2O2S crystal powd... more The present investigation explores the upconversion properties of Er3+- doped La2O2S crystal powder as well as its potentiality for anti-Stokes cooling. A detailed study of the wavelength and pumping power dependence of the spectroscopic properties and of the temperature field of samples with various erbium concentrations is presented. The analysis of both spectroscopic and thermal measurements shows that after a transient heating induced by the background absorption, cooling can be attained by means of anti-Stokes processes.
Proceedings of SPIE, Mar 7, 2016
Gadolinium oxysulfide crystal is a wide-gap semiconductor material known as an excellent host for... more Gadolinium oxysulfide crystal is a wide-gap semiconductor material known as an excellent host for trivalent rare-earth ions. The present investigation explores the upconversion and thermal properties of Er3+-doped Gd2O2S crystal powders as well as their potentiality for anti-Stokes cooling. A detailed study of the wavelength and pumping power dependence of the spectroscopic properties and temperature field for samples of various erbium concentrations is presented.
Optics Express, Nov 9, 2018
A new theoretical approach for random lasing of Nd 3+ doped powders is presented. The model's sin... more A new theoretical approach for random lasing of Nd 3+ doped powders is presented. The model's singularity lies in the fact that it proposes a probability distribution of the stimulated photon paths lengths in the sample, as well as a population inversion shared by different photon paths. The model's predictions satisfactorily compare with the results of laser threshold and absolute input/output energy slope of a real Random Laser. The main novel issue is that the best fit to the experimental results requires considering a high level of shared population inversion among different paths. The model simulation of local and spatially integrated Random Laser emissions, as well as their time evolution, is in accordance with the experimental behavior. These results also provide a new method of measuring the stimulated emission cross-section in this kind of random laser materials.
Optics Express, Jun 26, 2019
Optics Express, Jan 21, 2015
Optics Express, Mar 25, 2010
This investigation explores, for the first time, the random laser behavior of ground powder obtai... more This investigation explores, for the first time, the random laser behavior of ground powder obtained from organic-inorganic hybrid materials based on Rhodamine 6G incorporated into a di-ureasil matrix. The experimental results, both in the spectral and temporal domains, obtained by pumping with picosecond laser pulses, show the existence of efficient random laser emission in this system. Finally, the random laser performance is compared with the one of other Rhodamine-doped solid state silica compounds.
Optics Express, Apr 24, 2018
Optics Express, Jul 31, 2008
HAL (Le Centre pour la Communication Scientifique Directe), Feb 29, 2016
International audienc
The present work gives a detailed investigation of the dependence of the real time luminescence o... more The present work gives a detailed investigation of the dependence of the real time luminescence of Eu 3+-doped tin dioxide nanopowder on rare earth (RE) site symmetry and host defects. Ultrafast time-resolved analysis of both RE-doped and undoped nanocrystal powder emissions, together with electronic paramagnetic resonance studies, show that hostexcited RE emission is associated with RE-induced oxygen vacancies produced by the nonisoelectronic RE-tin site substitution that are decoupled from those producing the bandgap excited emission of the SnO 2 matrix. A lower limit for the host-RE energy transfer rate and a model for the excitation mechanism are given.
Optical Materials, May 1, 2009
One-and two-photon laser spectroscopy of Rhodamine 6G (Rh6G) and Coumarin 153 (C153) dyes embedde... more One-and two-photon laser spectroscopy of Rhodamine 6G (Rh6G) and Coumarin 153 (C153) dyes embedded in silica nanoparticles with and without TiO 2 scatters was investigated. Silica gel samples with different dye-doped nanoparticle concentrations were prepared as homogeneous bulk disks by the solgel method. Fluorescence and lifetime measurements were performed in the bulk matrices as well as in the resulting ground powders under one-and two-photon excitation. The effect of nanoparticles and TiO 2 scatters concentration on the lifetime quenching was evaluated. The results show a reduction of the fluorescence lifetime for increasing concentrations of both dye-doped nanoparticles and TiO 2 scatters. The fluorescence degradation under infrared ultrashort laser pulses was also explored as a function of irradiation time.
Optics Letters, Sep 12, 2013
The temporal dynamics of random laser emission from Nd-doped crystal powders has been investigate... more The temporal dynamics of random laser emission from Nd-doped crystal powders has been investigated by using an improved detection device. The precise conditions to detect high contrast, fast oscillations are described. The measured period is about one order of magnitude shorter than the one given in the literature for relaxation oscillations in these materials. The origin of these differences is discussed.
Journal of materials chemistry. A, Materials for energy and sustainability, 2018
Table S1. Thickness values of the films prepared by spin-coating on a glass substrate. Table S2. ... more Table S1. Thickness values of the films prepared by spin-coating on a glass substrate. Table S2. Molar extinction coefficient (ε) at 665 nm for chlorophyll ethanolic solutions and chlorophyll-doped hybrids. Table S3. Typical values for the electrical power interval available at a USB port and required to charge small electronic devices. The number and size of dU6-chl-based LSCs needed are also indicated. Fig. S1. Ellipsometric parameters Ic (black triangles) and Is (blue circles) measured for the active layer of (a) d-U(600), (b) t-U5000, (c) dU6-chl-2, (d) tU5-chl-2, (e) dU6-chl-3, (f) tU5-chl-3; the lines represent the best data fit (r 2 >0.9).
Materials, May 11, 2016
The efficient infrared-to-visible upconversion emission present in Er-doped lanthanum oxysulfide ... more The efficient infrared-to-visible upconversion emission present in Er-doped lanthanum oxysulfide crystal powders is used as a fine thermal sensor to determine the influence of upconversion processes on the laser-induced thermal load produced by the pump laser and to assess the potentialities of this material in order to obtain anti-Stokes laser-induced cooling. The analysis of the upconversion emission and excitation spectra as well as the decay curves indicates that energy transfer upconversion is the main mechanism responsible for the green (4 S 3/2) and red (4 F 9/2) upconversion luminescence. The dependence on temperature of the intensity ratio of upconversion emission from thermally-coupled 2 H 11/2 and 4 S 3/2 levels of Er 3+ in the 240-300 K temperature range has been used to estimate a relative sensitivity of 1.09ˆ10´2 K´1. Thermal measurements performed on the powder samples by using a thermal infrared camera exhibit a very inhomogeneous heat distribution at the sample surface due to the random distribution of the pumping energy inside the sample as well as to the random properties of the thermal field. The analysis of both spectroscopic and thermal measurements show that after a transient heating induced by the background absorption, cooling of discrete regions by means of anti-Stokes processes can be observed.
Optics Express, 2007
In this work, we report the optical properties of Tm 3+ ions in tellurite glasses (TeO 2-TiO 2-Nb... more In this work, we report the optical properties of Tm 3+ ions in tellurite glasses (TeO 2-TiO 2-Nb 2 O 5) for different Tm 3+ concentrations ranging between 0.05 and 1 wt%. Judd-Ofelt intensity parameters have been determined to calculate the radiative transition probabilities and radiative lifetimes of excited states. The stimulated emission cross-sections of the infrared emissions at 1487 nm and 1800 nm have been determined from the line shape of the emission spectra and the lifetimes of levels 3 H 4 and 3 F 4 respectively. The emission spectra obtained under 793 nm excitation reveal the existence of energy transfer via cross-relaxation among Tm 3+ ions. As a result, the intensity of the infrared 3 H 4 → 3 F 4 emission at 1487 nm decreases in relation to the one at 1800 nm, as concentration increases. The nonexponential character of the decays from the 3 H 4 level with increasing concentration indicates the presence of a dipole-dipole quenching process assisted by energy migration. The self-quenching of the 3 F 4 → 3 H 6 emission at 1800 nm can be attributed to limited diffusion within the active centers.
Materials, May 13, 2016
This work explores the room temperature random stimulated emission at 1.064 µm of a Nd:YAG crysta... more This work explores the room temperature random stimulated emission at 1.064 µm of a Nd:YAG crystal powder (Neodymium-doped yttrium aluminum garnet) in a very simple pump configuration with no assistance from an internal mirror. The laser threshold energy as a function of pump beam area and pump wavelength has been measured, as well as the temporal dynamics of emission pulses. The absolute energy of stimulated emission and the absolute laser slope efficiency have been measured by using a method proposed by the authors. The results show a surprising high efficiency that takes the low Nd 3+ ion concentration of the crystal powder into account.
Optics Express, Feb 13, 2023
Uploads
Papers by Sara García-Revilla