The purpose of this work is the study of laser cleaning of historical paper. The effect of laser exposure of the paper reflectance, fracture resistance and acidity was investigated. The paper surface ...roughness before and after laser treatment was analyzed by optical and scanning electron microscopy. It was shown that use of multi-pulse micromachining in combination with high-speed scanning of laser beams provides high safety for paper cleaning. The optimal parameters of laser radiation for effective and safe cleaning are a power density of about 2 × 105 W/cm2 at a wavelength of 1.06 μm, pulse repetition rate is 20 kHz; and a beam scanning speed of 200 mm/s–500 mm/s. The selective laser cleaning method for books and documents was proposed. Selective cleaning is achieved by means of high-precision control of the trajectory of movement of laser beams.
The study of the chemical composition of historical glasses is widely used in archaeometry. The results of such analyses provide information on the probable date, place, and technological features of ...their production. Over time, a weathered layer may form on the surface of the glass, which differs in composition from the original one. To determine the initial composition using conventional methods (for example, X-ray fluorescence spectroscopy), the weathered layer should be removed. For historical objects, such manipulation is unacceptable and should be minimized. One of the methods for analyzing the chemical composition with minimal damage to a sample is laser-induced breakdown spectroscopy. The aim of this work was to develop a LIBS method, which makes it possible to perform a quantitative analysis of lead silicate glasses, including glasses containing a weathered layer. Reference glasses with a variable content of potassium, silicon, and lead oxides were synthesized, and based on the LIBS spectra, a calibration dependence was obtained that made it possible to measure the concentration of lead and potassium oxides in glasses within 70–85 and 5–20 wt%, respectively. The method was applied to analyze the composition of the glaze on a historic glazed tile from the burial church in the Euphrosinian monastery in Polotsk (the second half of the 12th century AD). The crater formed with the laser beam on the glazed surface was about 200 microns. Such damage is negligible compared to the total surface area of the tile (~10 cm2). The thickness of the weathered glaze layer was 70 microns, which was determined using variation in lead oxide content.
This article presents the results of technical studies of the oil painting by the artist of German origin Werner Tübke “Hiroshima I” (1958). The creative heritage of this author has not been studied ...enough and represents scattered data on the technology of painting and artistic techniques. The aim of this work was to determine the art materials and painting technology described in his diaries, using the example of his only painting represented in Russia: “Hiroshima I”. For this purpose, an in situ approach was implemented using some simple museum instrumentations—UV-induced visible luminescence, infrared reflectography (IRR), radiography, portable X-ray fluorescence (XRF), Fourier transform Infrared spectroscopy (FT-IR), and polarizing microscopy using microprobes. As a result, the pigment composition of the painting layers could be determined, the painting technology refined, and a previously unknown hidden portrait of Werner Tübke’s father revealed.
Rare earth activated powders are widely regarded as promising candidates for optical thermometry due to their unique photoluminescence characteristics. The paper presents the structural and ...luminescent properties of crystalline powders of gadolinium and yttrium oxides (Gd1−xYx)2O3, doped with Nd3+ ions, synthesized by the liquid polymer-salt method. The addition of polyvinylpyrrolidone increases the homogeneity of the mixture and ensures high adhesion of the resulting powders. Scanning electron microscopy shows that powders are μm-sized aggregates, which consist of particles with several tens of nanometers in size. A smooth shift of the diffraction peaks of the powders occurs when Gd is replaced by Y without additional peaks. The successive decrease in the lattice constant of the powders from 10.816 to 10.607 Å confirms the existence of continuous solid solutions in the system. The Stark sublevels of the 4F3/2 → 4I9/2 fluorescent band are shifted to 4 nm when Gd is replaced by Y since the strength of the local field has a stronger effect on the inner F-shell of Nd ions in the case of Y. For thermometry, we chose the ratio of the fluorescence intensities between the Stark sublevels 4F3/2(2) → 4I9/2(2) and 4F3/2(1) → 4I9/2(2). The best obtained sensitivity is 0.22% °C−1 for Nd-doped GdYO3 powder in the range of 10–70 °C. This value of temperature sensitivity, together with radiation and excitation lying in the biological window, opens the possibility of using Nd3+-doped (Gd1−xYx)2O3 powders for real-time thermal probing of under tissue luminescence with sub-degree resolution.
A comparative study of spectral-luminescent and Judd–Ofelt analysis of photo-thermo-refractive (PTR) glasses doped with a variable content of neodymium (0.5–2.11 mol%) has been carried out for the ...first time. The change of Judd-Ofelt parameters (Ω2, Ω4, Ω6), radiation lifetime, experimental lifetime, branching ratio and emission cross sections were demonstrated as a function of Nd2O3 concentration and compared to the equivalent parameters in other works. It was found that the 4F3/2 → 4I11/2 transition is enhanced in Nd-doped PTR glass. The quantum efficiency of 0.5 mol% Nd-PTR for the same transition is 90.3% and the induced emission cross section is 1.743 × 10−20 cm2. The saturation intensity for 4F3/2 → 4I11/2 laser transition in the same sample is 20.62 kW/cm2, it is lower than that in some commercially produced glasses of same Nd3+-concentration. Laser action of a 0.5 mol% Nd-PTR was demonstrated, it was found that the round-trip loss of this gain medium is 0.34%, this value is quite low, and it is comparable to that in some commercially fabricated Nd-YAG crystals.
•We developed a chloride photo-thermo-refractive glass doped with ytterbium ions.•Spectroscopic and gain properties of ytterbium ions in chloride photo-thermo-refractive glass were carried ...out.•Ytterbium-doped chloride photo-thermo-refractive glass is a promising candidate material for laser and gain applications.
We developed a new chloride photo-thermo-refractive glass doped with ytterbium ions. The dependence of optical and spectral-luminescent characteristics on ytterbium concentration has been studied. Concentration dependence of excited state decay time has been analyzed taking into account the self-trapping and self-quenching mechanisms. The optimum concentration of ytterbium ions in chloride photo-thermo-refractive glass has been determined. Other important spectroscopic parameters such as absorption and emission cross-sections, radiative lifetimes, pump saturation, and minimum pump intensities have been obtained using absorption and emission measurements and theoretical approaches such as Fuchtbauer-Landenburg and McCumber theories. The evolution of the gain cross-section spectrum as a function of a population inversion parameter has been performed. Results of this study show that the ytterbium-doped chloride photo-thermo-refractive glass demonstrates good spectroscopic and luminescent properties for laser and gain application.
A study of the optical, spectral-luminescent and holographic properties of the chlorine-containing photo-thermo-refractive (PTR) glass doped with neodymium ions was carried out. The ...chlorine-containing PTR glass has been recently produced by replacing the bromine in the standard PTR glass with chlorine. The glass was doped with different concentrations of neodymium ions. The spectroscopic analysis of neodymium in the glass has been performed using the Judd-Ofelt theory based on experimental absorption and emission measurements. Spectroscopic parameters, such as the Judd-Ofelt intensity parameters, radiative and non-radiative transition probabilities, fluorescence lifetimes, stimulated emission cross-sections, and branching ratios, were obtained and found to be comparable with the parameters of the standard PTR glass doped with neodymium. The mechanism of non-radiative energy transfer was analyzed based on the lifetime kinetics measurements. It was found that cross-relaxation among neodymium ions is the dominant non-radiative energy transfer mechanism.
Holographic characteristics of the chlorine-containing PTR glasses doped with neodymium have been also studied. The volume Bragg grating was recorded in the doped and undoped glasses. It was found that the UV exposure and heat treatment do not change the spectroscopic characteristics of neodymium ions in the glasses, while the neodymium ions reduce the sensitivity of the glass. The energy transfer from cerium to neodymium when irradiating using the 325-nm laser makes the hologram recording possible on the samples of low neodymium concentrations only. Studying the spectroscopic and holographic properties of the chlorine-containing PTR glass doped with neodymium ions demonstrates the potential of using such a material in the applications of photonics integration and monolithic optical devices like distributed-feedback lasers.
•Spectroscopic properties of Nd ions in Cl-PTR glass are comparable to those of Nd in the standard (Br-PTR) glass.•VBG was recorded in the undoped Cl-PTR glass, as well as in the glass doped with Nd.•UV exposure and heat treatment do not affect the spectral-luminescent properties of Nd in the Cl-PTR glass.•Nd reduces the photosensitivity of Cl-PTR due to energy transfer from Ce to Nd during the hologram recording at 325 nm.
Spectral-luminescent characteristics of erbium ions in photo-thermo-refractive (PTR) glasses doped with different concentrations of ytterbium and erbium oxides were investigated in this work. X-ray ...diffraction pattern of studied glasses was carried out. Judd-Ofelt parameters of intensity Ωt were obtained and used for deriving emission cross-sections and radiative lifetimes. It was found that the peak emission cross-sections values at a wavelength of 1.53 μm obtained from F-L and McCumber methods are 0.59 × 10−20 cm2 and 0.60 × 10−20 cm2, respectively, which are very similar and compared with those of silicate glasses. A quite high value of quantum yield at the wavelength of 1.53 μm for the sample with 0.1 mol% Er2O3 co-doped with ytterbium oxide has been investigated. Energy transfer efficiency from ytterbium ions to erbium ones was found to be 80% and 86% for erbium- and 1 mol% and 2 mol% Yb2O3-co-doped PTR glass, respectively. Laser properties of 2Yb-01Er PTR glass were carried out. The gain spectrum starts to be positive when the population inversion parameter gets to 0.5. Laser action was demonstrated at room temperature. It was found that the round-trip losses of the Er/Yb-PTR element are 0.28%.
Optical materials doped with manganese ions have attracted interest as a red phosphor for warm white light LEDs. Lead-phosphate glasses are chosen for doping with manganese ions due to high ...refractive index of such material. In this study, new 50 PbO – 50 P2O5 – xMnO2 (x = 0.1, 1, 3, 5, 7, 10, 13 mol%) glasses are synthesized. To determine the optimal manganese ion concentration (to be used as the red phosphor) in those glasses, their spectral and luminescent properties are investigated. Mn2+ ions in lead-phosphate glasses have intense red luminescence in the wavelength range 620–690 nm. The Mn3+ ion to the total Mn ions ratio is found less than 0.1% based on the visible absorption spectroscopy data. Manganese ions in that glass are disposed at non-equivalent positions that results in nonexponential lifetime decay. The maximum absolute quantum yield value of Mn2+ ions is 49% in glass with 2.91 mol% MnO2.
YAG:Ce materials have been extensively studied as phosphors for blue to white light conversion. In the last years, the preparation methods of YAG:Ce powders in the nanometric scale have received ...intensive attention due to their special optical properties. In this context, the preparation of luminescent particles with high quantum yield (QY) and particle size in the deep submicrometer range is the main focus of this work. Amorphous and hexagonal YAG:Ce nanoparticles (<20 nm) with the stoichiometric composition of YAG:Ce were synthesized by liquid‐feed flame spray synthesis. The crystal phase, particle size, and specific surface area (SSA) evolution with the calcination temperature were investigated. A direct conversion from the amorphous/hexagonal phase to the cubic one was observed at T≥900°C, together with an increase in the particle size into the range 100‐350 nm and a corresponding decrease in the SSA. Zeta potential of the particles in aqueous dispersions and their photoluminescent properties were characterized. The QY increased for the phosphor powders with lower Ce3+ concentration. The highest QY of 70%‐72% was obtained for powders containing cerium doping of 0.1 mol% and spanning the size range between 130 and 270 nm.
