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Electrostriction, the deformation of dielectric materials under the influence of an electric field, is of continuous interest in optics. The classic experiment by Hakim and Higham [Proc. Phys. Soc. 80, 190 (1962)0370-132810.1088/0370-1328/80/1/322] for a stationary field supports a different formula of the electrostrictive force density than the recent experiment by Astrath et al. [Light Sci. Appl. 11, 103 (2022)2047-753810.1038/s41377-022-00788-7] for an optical field. In this work, we study the origin of this difference by developing a time-dependent covariant theory of optical force densities in photonic materials. When a light pulse propagates in a bulk dielectric, the field-induced force density consists of two parts: (i) The optical wave momentum force density fowm carries the wave momentum of light and drives forward a mass density wave of the covariant coupled field-material state of light. (ii) The optostrictive force density fost arises from the atomic density dependence of the electric and magneticfield energy densities. It represents an optical Lorentz-force-law-based generalization of the electro- and magnetostrictive force densities well known for static electromagnetic fields and derived from the principle of virtual work. Since the work done by fost is not equal to the change of the field energy density during the contraction of the material, we have to describe this difference with optostriction-related dissipation terms to fulfill the energy conservation. The detailed physical model of the dissipation is left for further work. The optostrictive force density can be understood in terms of field-induced pair interactions inside the material. Because of the related action and reaction effects, this force density cannot contribute to the net momentum transfer of the optical field. The theory is used to simulate the propagation of a Gaussian light pulse through a dielectric material. We calculate the electric and magnetic fields of the Gaussian light pulse from Maxwell's equations and simultaneouslysolve Newton's equation of motion of atoms to find how the velocity and displacement fields of atoms develop as a function of time under the influence of the field-induced force density.

Laser-induced wavefront distortion is detectable by several techniques based on the photothermal effect. The effect is probed by monitoring the phase shift caused by the bulging of the heated area, the photoelastic effects, and the spatial distribution of the refractive index within the sample and in the fluid surrounding it. A simple analytical solution for the wavefront distortion was only possible for low absorbing materials, with the assumption that the stresses obey either the thin-disk or the long-rod type distributions. Recently, a unified theoretical description for the laser-induced optical path change was proposed to overcome part of this limitation for weakly absorbing materials, regardless of its thickness. In this work, we perform an experimental investigation taking the sample–fluid heat coupling effect into account using the thermal lens technique. The experimental investigation presented here validates the unified model. In addition, we show that the heat-coupling model provides an alternative method to obtain physical properties of non-absorbing fluid by using a reference solid sample.

Thermal lens spectrometry has been utilized in various applications, and in some application areas, high sensitivity is required. In this work, a mode-mismatched thermal lens configuration probing thermal lens twice was developed for sensitivity enhancement. Experimental results exhibited that doubled sensitivity was achieved with this configuration compared with that attained with a conventional one, which was consistent with the prediction of the theoretical model for thermal lens spectrometry. As a result of the consistency, the linear absorption (attenuation) coefficient of de-ionized water at 532.3 nm was directly measured with this configuration and the conventional one and found to be (4.90 ± 0.05) × 10⁻² m⁻¹ and (4.7 ± 0.2) × 10⁻² m⁻¹, respectively. The results are in good agreement with accepted literature values. Theoretical analysis revealed that the sensitivity enhancement with this configuration is greater than that by simply doubling the sample thickness in a conventional configuration.

Freeze- and spray-dried inclusion complexes (ICs) of chlorhexidine (CHX) in β-cyclodextrin were characterized by Fourier transform (FT)-Raman, 1H nuclear magnetic resonance (NMR), and photoacoustic spectroscopy. The active Raman modes of CHX were simulated using the density functional theory. By considering semiempirical calculations, it was observed that the guest penetrates on the wider rim of the host in a proportion of 1:2. We observe from the FT-Raman analysis that the drying method influences the CHX:β-cyclodextrin conformational adjustment by the rearrangement of hydrophilic biguanides of the guest. The photoacoustic spectroscopy results inferred that the freeze-drying method provided a better inclusion due to a lower interaction between phenyl groups and hexamethylene of CHX. The freeze-dried IC achieved a faster dissolution pattern. These ICs provided immediate drug dissolution profiles in an aqueous medium better than a pure drug. The release profiles of freeze- and spray-dried ICs were explained by Fickian diffusion. These data support further planning and development projects of novel immediate release systems based on CHX.

Photoinduced expansion is a special property of chalcogenide glasses, which makes them useful for various applications in photonics. A clear understanding of the kinetics and the topography of photoinduced effects is fundamental to improve potential applications. A detailed study on bulk glass is performed using in situ Atomic Force Microscope measurements. The corresponding expected thermal contribution is obtained by numerical simulation using Finite Elemental Analysis method. The results show a significant difference between the dynamics of metastable/permanent and transitory effects, with the permanent photoexpansion being much larger in magnitude and slower in kinetics than the transient or reversible changes. The former effect is of athermal origin. However, the dynamic response of the latter is similar to that expected from thermoelastic expansion, suggesting a close correlation between the two effects, which remains to be established.

An extension of Drude–Lorentz model based on the fractional approach was used to investigate quantitative measurement of refractive index as a function of wavelength of Tellurite glasses. Tellurite glass samples were synthesized by conventional melt-quenching method with the composition of 65TeO2–15Li2O–20ZnO undoped and doped with different concentrations of Er2O3. Refractive index measurements were performed using the Brewster angle technique with polarized lasers at 442, 532, 594 and 633 nm as light source. From the Sellmeier’s coefficient it was possible to obtain the behavior of refractive index from 0.35 to 1.8 μm. The analytical solution obtained from the generalized Drude–Lorentz model was used to investigate the experimental data of refractive index behavior obtained by the two-pole Sellmeier’s equation showing that the mean polarizability increases with Er2O3 concentration and this behavior can be related to a collective fractal character of the material.

Tellurite glasses are good candidates for high-speed optical communications due to interesting properties and hence they present higher Raman cross section as compared to other glassy systems. In this work, tellurite glasses with 65TeO2-15Li2O-20ZnO (TLZ1) and 60TeO2-15Li2O-25ZnO (TLZ2) compositions and doped with different concentrations of Er2O3 (0.5; 1.0; and 2.0 mol%) were analyzed. The samples were synthetized by conventional melt-quenching method. The Raman gain coefficients of these glasses were obtained from Raman scattering experiments using 532 nm excitation. The Raman results presented a broad bandwidth from 225 to 1160 cm−1 that become broader with Er3+ concentration. Besides that, a slight difference on the 760 cm−1 band was observed with variation of the host composition. The Raman gain spectra presented a quenching effect for concentrations higher than 0.5 mol% and 1.0 mol% of Er2O3 for TLZ1 and TLZ2, respectively. This quenching have been attributed to the variation in TeOx units present in each composition. The Raman gain coefficient increased with Er3+ concentration and these values were two orders of magnitude higher than silicate glasses. Therefore, the materials studied present potential as new media for Raman amplifiers.

(100-X-Y)TeO2-XLi2O-YZnO, X = 10, 15 and 20, Y = 0, 5, 10, 15, 20, 25 and 30 mol%, glasses have been prepared by the melt quenching technique. Density and molar volume have been identified for every glass sample. Differential Scanning Calorimetry (DSC), optical absorption in the ultraviolet–visible region, Raman spectroscopy and linear refractive index have been achieved. DSC results show a considerable increase in glass stability with the replacement of TeO2 by ZnO. The Band Gap energy, determined from UV-VIS results, gradually increases in all set of samples. The Raman spectroscopy results confirm a structural change: with the increase of ZnO content (until TeO2 = 65 mol%), a decrease of non-bridging oxygens is verified, which decreases the polarizability of the system and increasing the Band Gap energy.

The mode-mismatched dual-beam thermal lens technique is widely applied in the characterization of optical and thermo-physical properties of solids and liquids. The technique has also been used to investigate transient acoustic waves induced by pulsed laser excitation at the nanosecond time scale. In this paper, we developed a semi-analytical model to describe the transient acoustic wave that allows a fitting procedure to get the physical properties of fluid samples. The method was used to investigate samples with different mixtures of ethanol and water, and quantitative information of piezo-optic coefficient and sound speed are evaluated for the fluid mixtures.

T m 3 + / H o 3 + -codoped low silica calcium aluminosilicate (LSCAS) glasses were prepared and characterized using optical absorption, luminescence decay, and thermal lens techniques. The emission band at 2.0 µm exhibited an enhancement when the Ho concentration was increased. The luminescence quantum efficiency values were determined for both 3 F 4 and 5 I 7 levels of T m 3 + and H o 3 + ions, respectively. The high decrease of the quantum efficiency of the 3 F 4 ( T m 3 + ) level for high H o 3 + concentration evidenced efficient energy transfer processes from T m 3 + to H o 3 + . The heat generated in the energy transfer processes were estimated via a thermal lens experiment, and a rate equation model was proposed to explain the obtained result. The experimental and estimated parameters with the proposed theoretical model are in good agreement. Finally, the results of this work suggest the T m 3 + / H o 3 + -codoped LSCAS is a promising material for applications using the emission around 2.0 µm that is of great interest for biomedical applications.

One of the most significant materials in a solar panel is the glass, which provides transparency, UV protection as well as mechanical and chemical resistance. In this work, we describe the production of prototypes of four solar modules made using borosilicate, zinc-tellurite, Pr$^{3+}$ doped zinc-tellurite, and float glass as cover materials. The performance of these prototypes was evaluated under a solar simulator, and a device was developed to monitor all prototypes under real conditions. A comparison between indoor and outdoor measurements shows that outdoor results are fundamental to evaluate the performance of modified solar modules as the ones considered in this study. In addition, we demonstrate the fundamental role played by the refractive index of cover glasses in the performance of the prototypes, and discuss how this feature could be explored to achieve enhanced devices, as well as other benefits that may arise from this field of research., Comment: 6 pages, 3 figures

Alternative fuels hold considerable promise as substitutes for petroleum diesel fuel. As such, biodiesel is a promising renewable fuel that has been developed and tested by a number of research groups. Quality control of this transportation fuel is of great significance to its commercialization. Conventional chromatographic and spectroscopic analytical methods are most commonly used for biodiesel characterization, in some cases yielding information detail beyond that needed for the determination of biodiesel quality. By contrast, less common methods, such as photothermal techniques, are well suited to characterize a wide range of transportation fuels. The complexities of photothermal and chemical analytical techniques are roughly similar, as are the costs. Photothermal methods are based on spectroscopic and thermophysical properties of the sample, an advantage with respect to ordinary chromatography and spectroscopy techniques. Furthermore, some photothermal techniques can be adapted for remote signal detection, which can be used for in situ analysis in fuel production for inline biodiesel quality inspection and control. Therefore, an overview and outlook of the photothermal characterization is of considerable interest. In this paper, the applications of photothermal techniques in the characterization of biodiesel, petroleum diesel fuels, and their blends are reviewed. The review includes thermophysical properties and correlations for fuels, determination of blend levels, and biodiesel stability investigations. After the review, discussion and perspective are presented for future improvement of photothermal characterization and industrial applications.

This work aimed to investigate and compare the composition and the physicochemical properties of 18 different sources of edible vegetable oils. A systematic study on the correlation between composition and physical properties was performed using Fourier Transform Infrared (FTIR) Spectroscopy and fatty acid chromatographic analysis. Principal component analysis of FTIR spectra is performed to classify edible oils concerning their physical properties. The results demonstrate the potentiality of the method associated with multivariate statistics analysis as powerful, fast, and non-destructive tools for characterization and quality control of edible vegetable oils.

We use the thermal lens technique in the nanosecond time scale to describe the acoustic wave effect in liquids and the corresponding correlation with the speed of sound in the fluid, volumetric thermal expansion, and piezo-optic coefficient. These physical properties are found to be directly correlated to the anomalous effects observed in the transients at the nanosecond time scale, where acoustic waves dominate the thermal lens signal inducing an oscillating transient. Our results suggest the application of the thermal lens to study the generation and the detection of thermo-acoustic waves in liquids, which makes this method interesting for all-optoacoustic ultrasound detection and imaging.

Antimicrobial resistance is a challenging health problem that demands alternative treatments. Nanoplatforms with antimicrobial properties, associated with photodynamic and photothermal therapies, are potential candidates for this task due to characteristics such as non-invasive, antibiotic-free, dual selectivity, and low adverse effects in therapeutic procedures. Graphene quantum dots are a possible substitute for other nanoparticles, especially by presenting low toxicity and low cost. However, graphene quantum dot properties are highly dependent on the synthesis methods, which makes it difficult to compare and improve methods using different studies. In this work, we apply spectroscopic and photothermal methods to investigate a commercially available green fluorescent graphene quantum dot (GQD) as a potential antimicrobial agent and to determine its theranostics properties. The results showed that the photoactivation of the GQD in phosphate-buffered saline solution by light sources with wavelengths shorter than the emission band can generate singlet oxygen and a heat yield of [Formula: see text] under excitation at 532 nm, showing the potential of this GQD as a photodynamic and photothermal agent.

We present a detailed spectroscopic study of photoluminescence in calcium aluminosilicate glasses doped with different concentrations of Pr 3 + (0.2, 0.5, 1.0 and 2.0 wt%). Optical transitions for the levels H 4 3 → P 0 , 1 , 2 3 ; I 6 1 ; D 2 1 ; G 4 1 ; 3 F 2 , 3 , 4 and H 6 3 have been observed using UV–Vis–NIR spectroscopy at room temperature. Emissions from levels P 0 3 and D 2 1 were detected and curves deviate from exponential behavior. Upconversion to UV was also observed when the samples were excited in the 3 P j 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 P 0 3 → F 2 3 and P 0 3 → F 4 3 suggests they are hypersensitive, although the 3 P 0 → 3 F 4 electronic transition does not entirely obey all the classic selection rules.

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 H 11 / 2 2 → I 15 / 2 4 and S 3 / 2 4 → I 15 / 2 4 transitions. Emission intensities at 992 and 1550 nm exhibit a relative increase with increasing doping concentration. Luminescence decay curves for the S 3 / 2 4 → I 15 / 2 4 transition follows a non-exponential behavior, while the I 11 / 2 4 → I 15 / 2 4 and I 13 / 2 4 → I 15 / 2 4 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.

Electromagnetic momentum carried by light is observable through the mechanical effects radiation pressure exerts on illuminated objects. Momentum conversion from electromagnetic fields to elastic waves within a solid object proceeds through a string of electrodynamic and elastodynamic phenomena, collectively bound by momentum and energy continuity. The details of this conversion predicted by theory have yet to be validated by experiments, as it is difficult to distinguish displacements driven by momentum from those driven by heating due to light absorption. Here, we have measured temporal variations of the surface displacements induced by laser pulses reflected from a solid dielectric mirror. Ab initio modelling of momentum flow describes the transfer of momentum from the electromagnetic field to the dielectric mirror, with subsequent creation/propagation of multicomponent elastic waves. Complete consistency between predictions and absolute measurements of surface displacements offers compelling evidence of elastic transients driven predominantly by the momentum of light., The exact mechanism of momentum conversion from light to an object has varied descriptions in the literature and experimental verifications are difficult. Here the authors do an in-depth experimental and numerical study of the momentum dynamics of elastic waves in a dielectric mirror hit by a pulsed laser beam.

Intense ultraviolet upconversion emission was produced in single Tm3+-doped OH--free low silica calcium aluminosilicate glasses. A new excitation route based upon multi-Stokes Raman emissions generated in an optical fiber pumped at 1.064 µm, and exploiting the absorption band around 1.2 µm by means of the 3H5 thulium excited state, was used. Furthermore, the other bands of the stimulated Raman scattering spectrum resonantly enhances all the upconversion processes, resulting in efficient ultraviolet (295 nm, 360 nm), blue (456 nm, 480 nm), red (650 nm, 667 nm), and near-infrared (800 nm) emissions. The population of the 1P0, 1D2, 1G4, 3F2 and 3H4 excited-state emitting levels was accomplished through stepwise multi-photon absorption. Results indicate competing cross-relaxation processes involving Tm3+ ion-pairs producing UV emission population quenching

Recent studies on laser induced thermal lens effect has made it possible to use this tool to investigate thermo-physical and chemical properties of biofuels. During laser illumination, a number of light induced effects may take place in the excited volume of the sample. However, the complexity of information included in the thermal lens transients could lead to misinterpretation of the results. This work examines the theoretical and experimental aspects that must be considered when performing biodiesel analysis using thermal lens spectrometry. The induction of photochemical reaction and thermal diffusion processes is carefully accounted for by describing the localized optical path change due to the concentration gradient created within the sample. We characterize mechanical, chemical and photochemical properties of thermal degraded biodiesels, enabling quantitative access of mass diffusion coefficient, photobleaching cross-section, and thermal yield. Dynamic viscosity analysis corroborates the results obtained by thermal lens, describing the method as very sensitive to thermal stability discrimination of biodiesel.

Laser induced wavefront distortion is critical for designing and evaluation of optical components for high-power laser and can affect performance and stability of optical systems. The analysis of this effect involves a complex thermoelastic problem only solved in simplified conditions such as the plane-stress or plane-strain configurations. For more realistic descriptions, numerical solutions are required, although recent advances allowed for a unified model to describe the optical path change, regardless of the sample thickness, assuming a sample of infinite radius. In this work, we extend this result for the case of a thick-disk sample by solving the set of differential equations governing the thermoelastic response for the finite radius configuration. These results could represent a significant contribution for designing and characterization of laser systems with potential application in many photothermal methods for material characterization.

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.

Four alternative fuels (AF) were blended with ultralow sulfur diesel (ULSD) at five different proportions (10, 20, 30, 50, and 100 vol % AF) to create 20 binary mixtures in this work. Two renewable jet AFs and two renewable diesel AFs were investigated. Interactions between the components in the mixtures were analyzed by means of spectroscopy (Raman, near-infrared), thermophysical (thermal diffusivity, thermo-optic coefficient), and physical (density) techniques. Correlations among the data were investigated using principal component analysis and partial least-squares regression. Trends in Raman intensities and band positions as well as thermophysical properties showed that the AF/ULSD blends resembled two-component mixtures despite the known complexities of the constituents. Specifically, spectra combined according to the percentages of the components in each mixture; thermophysical and physical properties exhibited similar behavior. The spectra showed strong correlations with all three physical properties, creating the possibility for predicting the properties of similar AF/ULSD mixtures. These properties are governed by the chemical compositions of the fuels.

We applied the open photoacoustic cell method operating at high frequency as an efficient and highly precise tool for the measurement of thermal properties of rubberized two-layer systems. The heat-coupling between the two layers is treated using the analogy between thermal and electrical resistances widely used in heat transfer problems. The thermal resistance between the two layers is considered effective and the problem is decoupled for each layer. Measurements are performed in two-layer samples of aluminum foil coated with layers of rubberized paint with different thicknesses. Thermal diffusivity and thermal conductivity are determined for the paint. The results are retrieved from the thermal resistance model assuming the effective thermal diffusivity of the composite material.

In this work, laser-induced Thermal Lens Temperature Scanning technique (TL-TS) is applied to evaluate oxidative stability and time of transesterification during biodiesel synthesis. Samples collected at different time intervals during the transesterification process of sunflower (SF) and soybean (SB) oils were submitted to fast oxidation through temperature scanning (between 22 and 190 °C), and simultaneously measured with the TL-TS technique. Temperature dependence of Thermal Lens effect amplitude showed the occurrence of oxidation, with the onset (Tonset) changing with the transesterification stages from 149 to 169 °C for sunflower and from 120 to 142 °C for soybean samples. The characteristic evolution of Tonset with reaction duration was estimated to be ∼7 min for sunflower and ∼10 min for soybean samples. The thermal diffusivity values were shown to be sensitive to rapid changes at transition temperatures, which could be related to molecular ruptures. Additional measurements were performed with DSC, TG and FTIR, to validate the information obtained by the TL-TS technique. In conclusion, the results showed the TL-TS technique as a promising tool for oxidative stability evaluation and determination of both chosen working temperature and minimal time interval for the solution to reach an optimized transesterification stage, thus contributing for reduction of costs, quality control and consequently for certification of biodiesel fuels.

Biodiesel susceptibility to oxidation is one of the major problems concerning its use as an alternative to diesel fuel. Although well-characterized, the oxidation process cannot be completely prevented since it can be affected by a large number of factors, such as fuel composition, storage conditions, contaminants, temperature, and the presence of air and light. In this work, we propose Fourier transform infrared spectroscopy (FTIR) in association with principal components analysis (PCA) and hierarchical cluster analysis (HCA) as a method for monitoring the extent of oxidation degree of biodiesel in the low rate phase, before the end of the induction period, in which the changes in the physical properties such as viscosity, mass density, and chain composition of the sample remain almost undetectable. A detailed investigation of thermo-oxidation of biodiesel is reported for a mixture of 50/50 (%) of soybean oil and animal fat biodiesels. The biodiesel degradation was accelerated when maintaining the temper...

Chromium-doped $$\alpha$$ - $$\hbox {Al}_{2}\hbox {O}_{3}$$ powder was synthesized by a modified sol–gel method using poly(vinyl alcohol) aqueous solutions and metal nitrate precursors. The synthesis process is simple, is of low cost and produced final crystals with cubic shape as confirmed by X-ray diffraction. The morphology of the samples verified by scanning electron microscopy showed slabs with thickness below 1 $$\upmu {\mathrm{m}}$$ , formed by interconnected long grains of typical thickness of around 200 $${\mathrm{nm}}$$ , showing growth of the grains as followed by thermogravimetric analysis. Luminescence characteristics of $$\hbox {Cr}^{3+}$$ were detected and analyzed as a function of the concentration of chromium using photoacoustic and photoluminescence spectroscopies.

Although nanocarrier systems have been investigated to function as therapeutic delivery agents to specific sites of the body, the drug encapsulation method is not always well elucidated. In this work, solid lipid nanoparticles (SLN) composed by stearic acid or cetostearyl alcohol were prepared by a hot homogenization method using poly(vinyl alcohol) or polysorbate as surfactant and loaded with hesperidin, a bioflavonoid that possesses many pharmacological properties. The obtained SLN were characterized by several physicochemical techniques to identify interactions between the constituents and to evaluate the drug incorporation into the nanoparticles. According to scanning electron microscopy and dynamic light scattering the hesperidin-loaded and unloaded SLN have spherical shapes, sizes ranging from 300 to 600 nm, zeta potentials varying from -35 to -20 mV, polydispersity indexes between 0.240 and 0.445, and entrapment efficiencies higher than 88%. X-ray diffraction showed the hesperidin amorphization due to its encapsulation in SLN, and also showed crystallization degree and polymorphic modification of the lipids after the SLN preparation. FTIR, Raman and Photoacoustic spectroscopy revealed no chemical reactions between drug and lipids, however, these results indicated that the drug was incorporated differently into nanoparticles based on the SLN composition. The analysis showed that stearic acid-based SLN prepared with polysorbate were more efficient to enclosure the hesperidin while the glycosydic part of the hesperidin was not entrapped in the cetostearyl alcohol-based SLN; instead, the hesperidin remained on the SLN surface due to lipid crystallization. The physicochemical characterization allowed identifying different types of hesperidin incorporation into the SLN, which can interact in a varied manner as targeted drug delivery systems.

We report on the thermoelastic properties of Ni 2 MnGa shape-memory alloys across the martensitic to austenitic phase transition using the time-resolved pump–probe photothermal mirror technique. Quantitative information on the thermo-mechanical characteristics of the sample are obtained and compared to specific heat measurements and differential scanning calorimetry (DSC) analysis. The thermal diffusivity varied remarkably within the martensitic–austenitic transition range. Both the amplitude signal and the thermal diffusivity present, in addition to the strong martensite to austenite phase transition, a clear evidence of a subtle second-order type phase transition close to 80 ° C. This magnetic transition is also observed in the calorimetric analysis. The transformation temperatures suggest the non-stoichiometric composition of sample, which is also revealed by non-symmetrical shapes of DSC peaks. The possible variation of the local chemical composition could be a result of gallium loss during the sample preparation or local inhomogeneity in the martensitic transformation.

Recent improvements in the modeling of photo-induced thermo–optical–mechanical effects have broadened the application of photothermal techniques to a large class of solids and fluids. During laser excitation, changes in optical reflectivity due to temperature variation may affect the photothermal signal. In this study, the influence of the reflectivity change due to heating is analyzed for two pump–probe photothermal techniques, thermal lens and thermal mirror. A linear equation for the temperature dependence of the reflectivity is derived, and the solution is tested using optical properties of semi-transparent and opaque materials. For semi-transparent materials, the influence of the reflectivity change in photothermal signals is less than 0.01%, while for opaque materials it is lower than 3%.

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.

We demonstrate the influence of edge effects on the photothermal-induced phase shift measured by a homodyne quadrature laser interferometer and compare the experiments with rigorous theoretical descriptions of thermoelastic surface displacement of metals. The finite geometry of the samples is crucial in determining how the temperature is distributed across the material and how this affects the interferometer phase shift measurements. The optical path change due to the surface thermoelastic deformation and thermal lens in the surrounding air is decoded from the interferometric signal using analytical and numerical tools. The boundary/edge effects are found to be relevant to properly describe the interferometric signals. The tools developed in this study provide a framework for the study of finite size effects in heat transport in opaque materials and are applicable to describe not only the phase shift sensed by the interferometer but also to contribute to the photothermal-based technologies employing similar detection mechanisms. Prikažemo vpliv robnih učinkov na fototermalno inducirani fazni premik, ki ga merimo s homodinskim kvadraturnim laserskim interferometrom in poskuse primerjamo z eksaktnimi teoretičnimi opisi termoelastičnih površinskih premikov kovin. Končna geometrija vzorcev je ključnega pomena pri določanju, kako se temperatura porazdeli po materialu in kako to vpliva na merjenje faznega premika interferometra. Razliko optične poti zaradi površinske termoelastične deformacije in termalne leče v okoliškem zraku dekodiramo iz interferometričnega signala s pomočjo analitičnih in numeričnih orodij. Mejni/robni učinki so pomembni za pravilen opis interferometričnih signalov. Orodja, razvita v tej študiji, nudijo okvir za preučevanje učinkov zaradi končnih dimenzij pri prenosu toplote v neprozornih materialih in niso uporabna le za opisovanje faznega premika, ki ga zazna interferometer, temveč prispevajo tudi k fototermalnim tehnologijam, ki uporabljajo podobne mehanizme zaznavanja.

The thermal-wave resonant cavity (TWRC) technique has been used for thermal diffusivity measurements by many researchers. This study aims to reduce the uncertainty associated with TWRC signal processing (curve fitting) by means of numerical simulation and experimental verification. Simulations show that the plot of signal amplitude versus cavity length can be fitted to a simplified model reported previously when the initial fitting position is at least twice the thermal-wave diffusion length (2 μg), and that the uncertainty caused by different end positions is negligible in the range of 6–10 μg. Upon consideration of the simulation results, signal-to-noise ratio, and clearly defined amplitude curve shape, fitting ranges of about 2.2–8.0 μg and 2.2–8.7 μg were chosen for the experimental data. Thermal diffusivity values (1.438 ± 0.001) × 10−7 and (1.436 ± 0.001) × 10−7 m2 s−1, respectively, were obtained for distilled water, in excellent agreement with the accepted literature value. The ratio of standard deviation to the mean value is smaller than 0.07%, one order of magnitude lower than typical results reported in the literature. Similar simulation results were obtained for air and methanol as intra-cavity samples.

Resumo Construímos uma plataforma de gravação magnética de fios a partir da sucata de um clássico gravador Webster-Chicago. O gravador de fios recuperado utiliza um motor para controlar engrenagens acopladas e mover carreteis que transportam um fio que passa por uma cabeça indutora. O som captado por um transdutor pode ser gravado diretamente no fio pela cabeça indutora e a mesma cabeça faz a leitura por um processo recíproco. Comparamos o sinal gravado direto da cabeça de gravação com o mesmo sinal com correção de distorção (polarização de corrente contínua e corrente alternada) e discutimos a relação sinal/ruído e a distorção de gravações em fios de aço.

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 P 0 3 → H 4 3 and D 2 1 → H 4 3 transitions were over 60% for both glass hosts, suggesting its potential use as solid-state laser devices.

Nowadays there exists a large variety of Ion Selective Electrodes with chalcogenide glasses as sensitive membrane. This short review paper will discuss the development of these sensors for the last almost fifty years. The glass compositions, response modelling, construction methods, parameters evaluation and applications are reviewed. Research breakthroughs and remaining problems on chalcogenide glass Ion Selective Electrodes are discussed.

Biofuels are an alternative to fossil fuels and can be made from many different raw materials. The use of distinct catalyst and production processes, feedstocks, and types of alcohol results in biofuels with different physical and chemical properties. Even though these diverse options for biodiesel production are considered advantageous, they may pose a setback when quality specifications are considered, since different properties are subject to different reactions during usage, storage and handling. In this work, we present a systematic characterization of biodiesels to investigate how accelerated thermal degradation affects fuel properties. Two different types of biodiesel, commercially obtained from distinct feedstocks, were tested. The thermal degradation process was performed by maintaining the temperature of the sample at $$140 \,^{\circ }\hbox {C}$$ under constant air flux for different times: 0 h, 3 h, 6 h, 9 h, 12 h, 24 h and 36 h. Properties such as density, viscosity, activation energy, volumetric thermal expansion coefficient, gross caloric value, acid value, infrared absorption, and temperature coefficient of the refractive index were used to study the thermal degradation of the biodiesel samples. The results show a significant difference in fuel properties before and after the thermal degradation process suggesting the formation of undesirable compounds. All the properties mentioned above were found to be useful to determine whether a biodiesel sample underwent thermal degradation. Moreover, viscosity and acid value were found to be the most sensitive characteristics to detect the thermal degradation process.

It now well known in laser materials, that a refractive index change appears when the active ions are pumped from ground to excited state due to the polarizability difference between ground and excited states (metastable). In this paper this effect was investigated in Tb3+ doped glasses: calcium alumino phosphate (CAP), low-silica calcium aluminosilicate (LSCAS) and calcium aluminosilicate (CAS). The measurements were performed using the time resolved Z-scan technique, with an Ar+ laser at 488 nm, close to the resonance of 7F6→5D4 absorption line, where 5D4 is a metastable state. We obtained for low-silica calcium aluminosilicate glass Δαp~10−24 cm3 which is the highest value ever reported for a RE doped material.

Thermophysical measurements and Raman spectroscopy were utilized to investigate 17 hydrocarbon distillates derived from Canadian oil sands in this work. Thermal lens and optical interferometer techniques were used to determine the thermal diffusivity ( D ) and temperature coefficient of the refractive index ( dn/dT ), respectively. It was found that D and dn/dT are closely correlated with the cetane numbers, distillation temperatures, monocyclic aromatics contents, and kinematic viscosities of the fuels. Raman spectra yielded information on the chemical compositions of the distillates, with aromatic contents proving to be particularly relevant. Multivariate analysis elucidated the relationships among the samples, their properties according to ASTM analyses, and the influence of composition on D and dn/dT .

The interaction between light and solid matter causes localized heating and surface displacement in the nanometer scale. The deformed surface can be analyzed by probing the time-dependent intensity of a laser reflected off of the surface using the thermal mirror (TM) method. This method provides quantitative measurements of thermal, optical and mechanical properties of a variety of materials. Here, we propose an alternative method to measure laser-induced surface deformation using atomic force microscopy (AFM). AFM is employed to determine the time evolution of the surface deformation and a theoretical model is proposed to determine physical properties of semi-transparent materials. The results are found to be in excellent agreement compared to those obtained using TM.

An adaptive spatial filter is used as an optical novelty filter to detect photothermal mirror (PM) signals in high absorbing materials using continuous wave laser excitation. The optical novelty filter uses an optical beam-fanning limiter based on single domain barium titanate (BaTiO3), cut and poled 45° relative to the c-axis. The optical novelty filter approach relaxes the requirement for high sample surface smoothness because the effect aperture adapts to the surface, reducing the stationary background from the optical signal and provides a means of developing the photothermal mirror signal. Time-dependent probe laser phase shifts due to photothermal surface deformation pass through the optical novelty filter and are detected as an intensity increase over the stationary or “mundane” signal. Experimental studies are performed using four well-characterized metals using both the conventional photothermal mirror and optical novelty filter apparatuses in order to understand the complicated signal behavior. Signal behavior is analyzed in different excitation intervals using pseudo-chopped sample excitation with different duty cycles. Optical novelty filter signals show fast response for changes in the spatial beam profile followed by long relaxation time. Reasons for the optical novelty filter response are described.

Strong light absorption and high levels of singlet oxygen production indicate erythrosin B as a viable candidate as a photosensitizer in photodynamic therapy or photodynamic inactivation of microorganisms. Under light irradiation, erythrosin B undergoes a photobleaching process that can decrease the production of singlet oxygen. In this paper, we use thermal lens spectroscopy to investigate photobleaching in micellar solutions of erythrosin ester derivatives: methyl, butyl, and decyl esters in low concentrations of non-ionic micellar aqueous solutions. Using a previously developed thermal lens model, it was possible to determine the photobleaching rate and fluorescence quantum efficiency for dye-micelle solutions. The results suggest that photobleaching is related to the intensity of the dye-micelle interaction and demonstrate that the thermal lens technique can be used as a sensitive tool for quantitative measurement of photochemical properties in very diluted solutions.

Tb3+ doped materials exhibit strong emission in the green (5D4) and weak emission in the UV-blue (5D3) regions. The blue emission can occur from direct UV excitation or by excited state absorption, through 5D4 metastable level. In this paper, we investigate the effect of silica content on the spectroscopic properties of the Tb3+ doped calcium aluminosilicate glasses. The low silica calcium aluminosilicate glass (LSCAS) and calcium aluminosilicate glass (CAS) doped with 0.5 wt% of Tb3+ were prepared and characterized through absorption, excitation, Stokes emission, upconversion emission and 5D4 lifetime decay measurements. The green luminescence in the LSCAS glass presented a fast quenching. The silica influence on this behavior was discussed and a comprehensive interpretation is presented, correlating the Tb3+ luminescence behavior with the silica concentration. Additionally, we analyze the excited state absorption effect on fluorescence transients to 5D4 energy level lifetimes.