Eosin Y is known to be a powerful probe of biological molecules and an efficient photosensitizing agent for the production of singlet molecular oxygen. Under continuous laser excitation, degradation ...through photobleaching is observed in aqueous solutions of eosin Y; this process is driven by the production of singlet oxygen. Optical bleaching in aqueous solutions is known to yield anomalous thermal lens transient signals, which can be evaluated by modeling the relaxation processes that give rise to the generation of heat in the solution. A model describing photobleaching in the thermal lens transient signal is derived and is applied to investigate eosin Y in aqueous solutions at different temperatures. Using this model, quantitative information regarding the molecular diffusion rate, optical bleaching, and fluorescence quantum efficiency is obtained.
•Eu2+ valence state was obtained in sodium silicate glasses. Excitation band was observed 100 nm wider than most materials.•The excitation band overlaps perfectly with the solar spectrum emission in ...UV–VIS region, providing conversion of the energy in c-Si cell.•Eu2+Nd3+ co-doped glass presented an excellent match between the Nd3+ emission and the optimal photoconversion energy.
The challenge of modifying the solar spectrum intensifies efforts in the pursuit of enhanced materials and optical systems. In this work, we present novel and efficient near infrared-emitting Eu2+ and Nd3+ co-doped sodium calcium silicate glasses. Optical absorption, excitation spectra, emission decay time, were measured and discussed as a function of Nd2O3 content. Laser power-dependent emission intensity was used to evaluate the transfer mechanism, and an energy level diagram was proposed. For the sample doped with optimized neodymium content, energy transfer efficiency reached 70%. For co-doped samples, the excitation spectrum was broadly intense and perfectly overlapped with the solar spectrum in the NUV region. Therefore, NUV/Visible can be efficiently converted into NIR, precisely where the C-Si response is maximal, through the Eu2+→Nd3+ pathway. This work’s outcomes made the focused materials worthy for solar cell applications, optimizing energy conversion lost by thermalization, into useful energy.
We present semi-analytical solutions describing the spatiotemporal distributions of temperature and pressure inside low-absorbing dielectrics excited by tightly focused laser beams. These solutions ...are compared to measurements in water associated with variations of the local refractive index due to acoustic waves generated by electrostriction, heat deposition, and the Kerr effect at different temperatures. The experimental results exhibited an excellent agreement with the modeling predictions, with electrostriction being the dominant transient effect in the acoustic wave generation. Measurements at 4.0∘C show that the thermoelastic contribution to the optical signal is significantly reduced due to the low thermal expansion coefficient of water at this temperature.
•Thermal Lens effect is analyzed on time-resolved Z-scan in the cw-single beam configuration.•The difference between both thermal and electronic effects on Z-scan method is assessed and ...quantified.•The use of cw lasers in time-resolved Z-scan is evaluated in materials with slow response time.•The method is applied on the determination of small absorption of a host glassy matrix.
Thermal lens and Z-scan have been the two most important and used techniques for determining third-order nonlinear optical properties and photothermal properties of optical materials. Both methods have response to thermal and electronic effects, depending on the magnitude of each effect and the experimental arrangement, one method becomes more suitable than the other in order to determine the desired property. In this paper the thermal lens effect is analyzed on time-resolved Z-scan measurements in the cw-single beam configuration. A ruby sample, which presents predominantly electronic effect, is compared to samples presenting predominant thermal effects. The theoretical and a complete experimental description are presented. The difference between both thermal and electronic effects on Z-scan method is assessed and quantified.
The small energy difference between the fundamental level and the first opposite parity configuration of Pr3+-doped hosts is particularly challenging for the characterization of radiative transitions ...using the Judd-Ofelt theory, although modified versions of the theory have been proposed in the past for the investigation of praseodymium doped materials. Here, we present a detailed spectroscopic investigation on two sets of calcium aluminosilicate glasses, with 34 wt% of SiO2 (CAS) and with 7 wt% of SiO2 (LSCAS), doped with different concentrations of Pr3+ (0.5, 1.0 and 2.0 wt%). We use the standard Judd-Ofelt theory to characterize the glasses and the results and derived spectroscopic quantities — such as transition probabilities, radiative lifetimes and branching ratios — are compared to results obtained by the modified Judd-Ofelt theories. The analysis showed that the modified theories could lead to smaller values of root mean square deviations. However, a better agreement between experimental data and the standard theory was achieved when the derived spectroscopic quantities are taken into account. Moreover, the branching ratios of the P03→H43 and D21→H43 transitions were over 60% for both glass hosts, suggesting its potential use as solid-state laser devices.
•Comparation between three different Judd-Ofelt theories for Pr3+-doped glasses.•Spectroscopic properties were derived and compared with the theories.•Branching ratio suggests a potential candidate for solid-state laser devices.
This paper reports on a study aimed at investigating the physical properties and radiation shielding capability of a low-cost, high-transparency silicate glassy system reinforced with barium oxide. ...The prepared glasses' elementary and modified network structures were analyzed using X-ray diffraction and Raman spectroscopy, confirming their glass nature and revealing the progressive network depolymerization with BaO inclusion. Differential scanning calorimetry was employed to determine the glass transition temperature, which showed an increase with increasing BaO content. Tauc's plot was used to study the direct optical bandgap, which was observed to increase from 3.91 to 4.75 eV with BaO content from 0 to 30 mol%, linked to an increase in the average oxygen bond chain length and non-bridging oxygen atoms' creation. The density, molar volume, and oxygen packing density of the glass were found to increase with BaO addition, indicating that barium oxide promotes the formation of a compact network structure collapsing into a closely packed arrangement. At an X-ray energy of 40 keV, the mass attenuation coefficient increased from 0.67 to 11.48 cm2/g with BaO content. To assess the efficacy of theoretical calculations, we have conducted an experimental setup to measure the linear attenuation coefficient using an 241Am (59.5 keV) radiation source. Finally, the gamma shielding effectiveness was evaluated, and the sample containing 30 mol% of BaO showed superior radiation protection compared to concrete and was comparable to RS360 commercial glass.
•Newly Lead-free shielding glasses with exceptional physical and structural properties.•Groundbreaking radiation attenuator material that maintains over 90 % optical transmittance in the UV–VIS–NIR spectra range.•Highly effective fast neutron removal cross-section comparable to concrete, providing superior neutron protection.•Significant enhancement of up to almost 20-fold in X-ray blocking capability of glasses enriched with BaO.
In this study, luminescence properties of Tb3+-doped low silica calcium aluminosilicate glasses are analyzed as a function of Tb3+ concentration (0.04–15.0 wt%). Decay curves for the 5D3 level are ...found to be non-exponential for all Tb3+ concentrations due to ion–ion energy transfer through cross-relaxation process. To identify the origin of the energy transfer mechanism, the decay curves were well fitted by Inokuti–Hirayama model (s = 6), which indicates that the energy transfer process is related to dipole–dipole interaction. Trivalent Tb-doped materials normally exhibit stronger green emission compared to blue emission, a feature that increases with Tb3+ concentration and is attributed to the cross-relaxation process. In this paper, we show a remarkable blue emission in comparison to other Tb3+-doped glasses. A theoretical model for the blue and green emissions, from 5D3 and 5D4 levels respectively, was proposed to establishing a link between the color emission and the 5D3 lifetime quenching due to a cross-relaxation process. This model was successfully applied to the experimental results of this paper as well as previous data in the literature.
•Evaluation of the color-tunable properties of a series of Tb3+-doped, OH-free aluminosilicate glasses.•A novel quantitative model explains the link between fluorescence decay quenching and the evolution of blue/green emissions.•The critical role played by some host glass properties such as phonon energy and synthesis methods.
Time-resolved Z-scan measurements were performed in Tb3+-doped Zinc Phosphate (PZABP) glasses. The electronic and thermal contributions to the Z-scan signal were unequivocally discriminated. The ...electronic component was shown to increase linearly with the Tb3+ concentration in the glasses and explained by the polarizability difference (Δαp) between excited and ground states of the Tb3+ ions. Open aperture Z-scan measurements indicate the presence of excited state absorption due to a spin-forbidden transition from the metastable (5D4) 4f level of Tb3+ to the 4f75d1 state. The Δαp value obtained in the PZABP glass matrix is two orders of magnitude smaller than the observed in aluminosilicate glasses, indicating that Δαp of Tb3+-doped materials is very sensitive to the host crystal field, as compared to other rare-earth ions such as Nd3+ and Yb3+. These results are justified by the host dependence of energy position of the 4f75d1 levels of Tb3+.
•Nonlinear optical characterization of Tb3+-doped zinc phosphate glass, a candidate for laser active media.•Distinction of electronic and thermal contributions on Z-scan measurement of Tb3+-doped zinc phosphate glass.•The use of cw lasers in time-resolved Z-scan is evaluated in materials with slow response time.•The method is applied on the determination of small absorption of a host glassy matrix.•Tb3+-doped zinc phosphate glass presented a polarizability difference nearly 20 times lower than the observed in Tb3+-doped calcium aluminosilicate glasses.
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