The interaction of localized light with matter generates optical electrostriction within dielectric fluids, leading to a discernible change in the refractive index of the medium according to the ...excitation's light profile. This optical force holds critical significance in optical manipulation and plays a fundamental role in numerous photonic applications. In this study, we demonstrate the applicability of the pump-probe, photo-induced lensing (PIL) method to investigate optical electrostriction in various dielectric liquids. Notably, the thermal and nonlinear effects are observed to be temporally decoupled from the electrostriction effects, facilitating isolated observation of the latter. Our findings provide a comprehensive explanation of optical forces in the context of the recently introduced microscopic Ampère electromagnetic formalism, which is grounded in the dipolar approximation of electromagnetic sources within matter and characterizes electrostriction as an electromagnetic-induced stress within the medium. Here, the optical force density is re-obtained through a new Lagrangian approach.
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.
We propose a combined pump-probe optical method to investigate heat diffusion properties of solids. We demonstrate single-shot simultaneous laser-induced thermoelastic surface displacement of metals ...detected by concurrent measurements using photothermal mirror and interferometry. Both methods probe the surface displacement by analyzing the wavefront distortions of the probe beams reflected from the surface of the sample. Thermoelastic properties are retrieved by transient analysis in combination with numerical description of the thermoelastic displacement and temperature rise in the sample and in the surrounding air. This technique presents a capability for material characterization that can be extended to experiments for quantitative surface mapping.
Photoactivation of Erythrosine in simulated body fluids Bergmann, Eduardo V.; Capeloto, Otávio A.; Catanio, Angelo T.S. ...
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy,
10/2021, Letnik:
259
Journal Article
Recenzirano
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•Photoactivation process of Erythrosine was investigated in different simulated body fluids.•Optical techniques were used to investigate the photoactivation process.•Thermal lens ...results reveled photobleaching in submicromolar concentrations range.•Clear differences in the photodegradation kinetics, triplet lifetime and singlet oxygen generation were observed.•The results presented could help to explain and to define Photodynamic Therapy application protocols.
Photodynamic Therapy (PDT) is a powerful technique for the treatment of cancer and non-cancerous diseases. The precise PDT treatment protocol definition must consider the performance difference between in vitroand in vivoapplications. This also occurs in other biological studies, and to partially overcome this difficulty, the simulated body fluids are generally applied as a prior understanding of the particularities of the different systems. However, in PDT these studies are scarce. In this work, we investigated the photoactivation of Erythrosine, a photosensitizer widely used in PDT, in different simulated body fluids. Differences in the photodegradation kinetics, triplet lifetime, and singlet oxygen generation were observed. The results can help to explain and to define PDT application protocols.
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.
We demonstrate the Soret effect in a lyotropic liquid crystal at different temperatures across the isotropic phase detected by the time-resolved thermal lens technique. We investigate thermo-optical ...and mass diffusion properties of the sample and present quantitative characterization of Soret, mass and thermal diffusion coefficients. The results reveal that the temperature gradient induced in the experiments causes the migration of micelles from hotter to colder regions in the sample. The increase of the mass diffusion coefficient with temperature is related to the decrease of the radius of the micelles in the solution.
•Soret effect in a lyotropic liquid crystal at different temperatures across the isotropic phase;•Investigation of thermo-optical and mass diffusion properties;•Quantitative characterization of Soret, mass and thermal diffusion coefficients;•The temperature gradient in the experiments causes the migration of micelles from hotter to colder regions in the sample;•The increase of the mass diffusion coefficient with temperature is related to the decrease of the radius of the micelles.
This work presents a spectroscopic investigation of tellurite glasses with the composition 65TeO2-15Li2O-20ZnO doped with different concentrations of Er2O3. Optical absorption and emission ...spectroscopy were performed at room temperature to determine emission properties of Er3+ in the visible and near-infrared regions. The samples presented intense green emission due to the H11/22→I15/24 and S3/24→I15/24 transitions. Emission intensities at 992 and 1550 nm exhibit a relative increase with increasing doping concentration. Luminescence decay curves for the S3/24→I15/24 transition follows a non-exponential behavior, while the I11/24→I15/24 and I13/24→I15/24 transitions presented simple exponential behavior with high lifetime values. Under 975 nm excitation, upconversion luminescences in the green and red regions are observed, with a relative increase for red emission as function of doping concentration. The possible mechanisms considering multi-phonon relaxation, energy transfer and cross-relaxation processes were discussed for green and red emissions under excitations at 488 and 975 nm. The square dependence of green emission on the excitation power indicates two photons contribution to the upconversion emission. The full width at half-maximum values of emission at 1550 nm increased with increasing Er3+ concentration, showing the potential of the studied material as infrared amplifier.
We present a detailed spectroscopic study of photoluminescence in calcium aluminosilicate glasses doped with different concentrations of Pr3+ (0.2, 0.5, 1.0 and 2.0 wt%). Optical transitions for the ...levels H43→P0,1,23; I61; D21; G41; 3F2,3,4 and H63 have been observed using UV–Vis–NIR spectroscopy at room temperature. Emissions from levels P03 and D21 were detected and curves deviate from exponential behavior. Upconversion to UV was also observed when the samples were excited in the 3Pj level, populating 4f5d upper level — via energy transfer upconversion and/or excited state absorption — which decays emitting UV light. In addition, the unusual variation of the peak intensities of transitions P03→F23 and P03→F43 suggests they are hypersensitive, although the 3P0→3F4 electronic transition does not entirely obey all the classic selection rules.
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