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The polymeric optical fibre technology can be successfully used for UV spectrum range radiation measurements.Anew type of fluorescent optical fibre optode is presented. The used fluorescent wave-shifter was used for UV-VIS conversion and radiation measurements. The linear characteristic with sensitivity 480 mW−1 is presented for UV range 7.2-13.6 mW. Presented optode construction advantages (small dimensions, low weight, high immunity to electromagnetic fields and distributed sensor architecture possibility) are attractive for numerous composite based engineering applications.

In the paper the luminescence optical fiber used as a temperature sensor is presented. The new construction of rhodamine B doped, polymethyl methacrylate optical fibre with silver coating is shown. The fabrication process and luminescent properties of rhodamine B in sensing fibre are investigated. The attenuation and spectral shift of luminescence peak vs. the fibre length were measured and used for optimization of sensor construction. The characteristics of sensor for temperature range from 293 up to 343 K are shown. The relative sensitivity equal to -5:4 × 10-4 K-1 was obtained. The article presents also the potential applications of presented sensor. [ABSTRACT FROM AUTHOR]

The article presents physicochemical, thermal and spectroscopic properties of two different glass systems: TeO2-GeO2-PbO-PbF2- BaO-Nb2O5-LaF3 and SiO2-Al2O3-Sb2O3, co-doped with Yb3+/Tm3+ ions. Blue upconversion luminescence at a wavelength of 478 nm corresponding to the thulium 1G4 ⇥3H6 transition was observed under 976 nm pump radiation in both of the co-doped glasses. This indicated the existence of efficient Yb3+ ⇥ Tm3+ energy transfer via three-photon absorption mechanism. Thermal and optical results substantiate the claim for practical applicability of the manufactured glasses in design of optical fiber sources. [ABSTRACT FROM AUTHOR]

In the paper the spectroscopic properties of antimony-germanate glass co-doped with Yb3+/Ho3+ has been investigated. Fabricated Yb3+/Tm3+/Ho3+ co-doped glass is characterised by the emission of simultaneous multicolour upconversion luminescence. Strong blue 1G4 → 3H6 (Tm3+), green 5F4 → 5I8 (Ho3+) and red 5F5 → 5I8 (Ho3+) upconversion emission bands have been measured under 976 nm excitation at room temperature. Influence of molar ratio of active ions and excitation power on the colour coordinates (CIE-1931) have been investigated. [ABSTRACT FROM AUTHOR]

The infrared emission of Tm3+/Ho3+-doped antimony-silicate optical fiber has been presented. Luminescence at 2.1 μm corresponding to 5I7 → 5I8 transition in holmium was obtained by energy transfer between Tm3+ and Ho3+ ions. According to the Forster-Dexter theory, the efficiency of energy transfer of the 3F4 (Tm3+) → 5I7 (Ho3+) transition was calculated. The optimization of the activator content and the donor (Tm3+)/acceptor (Ho3+) ions concentration ratio were conducted with the purpose of maximizing the efficiency of energy transfer. It made possible to select best-suited glass which was used to manufacture double-clad optical fiber. Strong and narrow bands of amplified spontaneous emission which formed as a result of energy transfer between thulium and holmium ions were observed in the fiber under exciting with radiation at 795 nm wavelength. [ABSTRACT FROM AUTHOR]

In the article the cooperative energy transfer in Ge02-GaO-BaO glass system doped with Yb3+/Tb3+ under 980 nm laser diode excitation was investigated. The influence of Tb3+ concentration on the luminescent properties was determined. Measured strong luminescence at 489, 543, 586, 621 corresponds to 5D4→7FJ (J = 6, 4, 3) transitions and luminescence at 381, 415, 435 nm results from 5D3, 5G6→7FJ (J = 6, 5, 4) transitions. Mechanism and energy diagram involved in observed emission were discussed. The highest upconversion emission intensity was obtained in the germanate glass doped with 0.7 Yb2O3/0.7 Tb2C>3. [ABSTRACT FROM AUTHOR]

In the article there are presented two different series of glass: fluorophosphate with molar composition: 65P2O5-8Al2O3-2BaO-5BaF2-6ZnF2-5Na2O-6MgF2-3B2O3 and antimony glasses 40Sb2O3-3Al2O3-57SiO2 doped with Nd3+ and Yb3+ ions. Dopant contents influence efficient spatial overlapping of emission level for neodymium and absorption level for ytterbium was analyzed. While exciting the produced glasses with a laser diode (λ = 808 nm) a broad luminescence spectrum (Δλ = 100 nm) has been obtained in both cases in the vicinity of 1 μm, being the superposition of the following transitions: 4F3/2→4I11/2 for Nd3+ and ²F5/2→²F7/2 for Yb3+. Based on the luminescence measurements the probability of non-radiative energy transfer was described. Because of a small difference in energy (≈ 1190 cm-1) between the laser levels of neodymium and ytterbium the resonant process of energy transfer has been obtained. [ABSTRACT FROM AUTHOR]

Compact fluorescent optical fibre illuminator is presented. The fabrication and characterisation of polymethyl methacrylate fibre with fluorescent tip are presented. The luminescent properties of Perylene (Per) and Rhodamine 6G (Rh 6G) of co‐doped polymeric fibre were used for 405 nm laser diode radiation conversion inside the polymeric fibre. The spectrum shape and chromaticity coordinates show possibility of application as white light (ca. 3350 K) illuminator. The intensity characteristics of fabricated illuminator are also shown. The small dimensions and high flexibility assure numerous applications of presented construction. [ABSTRACT FROM AUTHOR]

Progress in UV treatment applications requires new compact and sensor constructions. In the paper a hybrid (organic-inorganic) rare-earth-based polymeric UV sensor construction is proposed. The efficient luminescence of poly(methyl) methacrylate (PMMA) matrix doped by europium was used for testing the optical sensor (optrode) construction. The europium complex assures effective luminescence in the visible range with well determined multi-peak spectrum emission enabling construction of the optrode. The fabricated UV optical fibre sensor was used for determination of Nd:YAG laser intensity measurements at the third harmonic (355 nm) in the radiation power range 5.0-34.0 mW. The multi-peak luminescence spectrum was used for optimization of the measurement formula. The composition of luminescent peak intensity enables to increase the slope of sensitivity up to −2.8 mW-1. The obtained results and advantages of the optical fibre construction enable to apply it in numerous UV detection systems.

A new type of luminescent optical fibre sensor for structural health monitoring of composite laminates (CFRP) is proposed. The Nd3+ doped multi-core doubleclad fibre incorporated in composite structure was used as a distributed temperature sensor. The change of luminescence intensity (Nd3+ ions) at the wavelength of 880 nm (4F3/2 → 4I9/2) and 1060 nm (4F3/2 → 4I11/2) was used for internal temperature monitoring. The special construction of optical fibre was used as it assures an efficient pumping mechanism and, at same time, it increases the measuring sensitivity. The linear response with relative sensitivity 0.015 K−1 was obtained for temperature range from 30 up to 75ºC. The manufacturing process of CFRP with embedded optical fibre sensor is also discussed.

LMA (Large Mode Area) optical fibers are presently under active investigation to explore their potential for generating laser action or broadband emission directly within the optical fiber structure. Additionally, a wide mode profile significantly reduces the power distribution density in the fiber cross-section, minimizing the power density, photodegradation, or thermal damage. Multi-stage deposition in the MCVD-CDT system was used to obtain the structural doping profile of the LMA fiber multi-ring core doped with Tm 3+ and Tm 3+ /Ho 3+ layer profiles. The low alumina content (Al 2 O 3 : 0.03wt%) results in low refractive index modification. The maximum concentrations of the lanthanide oxides were Tm 2 O 3 : 0.18wt % and Ho 2 O 3 : 0.15wt%. The double-clad construction of optical fiber with emission spectra in the eye-safe spectral range of (1.55-2.10 µm). The calculated LP 01 Mode Field Diameter (MFD) was 69.7 µm (@ 2000 nm, and 1/e of maximum intensity), which confirms LMA fundamental mode guiding conditions. The FWHM and λmax vs. fiber length are presented and analyzed as a luminescence profile modification. The proposed structured optical fiber with a ring core can be used in new broadband optical radiation source designs.

The near-infrared emission in fabricated low-phonon energy, gallo-germanate glass, and double-core optical fiber has been investigated. Broadband amplified spontaneous emission (ASE) was obtained in optical fiber with cores doped with: 1 st - 0.2Er 2 O 3 and 2 nd - 0.5Yb 2 O 3 /0.4Tm 2 O 3 /0.05Ho 2 O 3 as a result of the superposition of emission bands from both cores corresponding to the Er 3+ : 4 I 13/2 → 4 I 15/2 (1 st core) and Tm 3+ : 3 F 4 → 3 H 6 /Ho 3+ : 5 I 7 → 5 I 8 (2 nd core) transitions. The effect of fiber length and pump wavelength on the near-infrared amplified spontaneous emission (ASE) properties has been analyzed for 1 m and 5 m optical fiber. The widest emission bandwidth (355 nm - 3 dB level) was obtained for a 5 m length optical fiber pumped by a 940 nm laser.

Double-clad optical fiber with a multi-ring core profile doped with thulium and holmium fabricated by Modified Chemical Vapor Deposition Chelate Doping Technology (MCVD-CDT) is presented. The measured Tm 2 O 3 and Ho 2 O 3 complexes' weight concentrations were 0.5% and 0.2% respectively. Numerical analyses show weakly guiding conditions and 42.2 µm of MFD LP 01 at 2000 nm. The low NA numerical aperture (NA = 0.054) was obtained for the 20/250 µm core/cladding ratio optical fiber construction. The emission spectra in the range of 1.6-2.1 µm vs. the fiber length are presented. The full width at half maximum (FWHM) decreases from 318 to 270 nm for fiber lengths from 2 to 10 m. The presented fiber design is of interest for the development of new construction of optical fibers operating in the eye-safe spectral range., (© 2023. Springer Nature Limited.)

An investigation of fluoroindate glass and fiber co-doped with Yb 3+ /Er 3+ ions as a potential temperature sensor was assessed using the fluorescence intensity ratio (FIR) technique. Analysis of thermally coupled levels (TCLs- 2 H 11/2 and 4 S 3/2 ), non-thermally coupled levels (non-TCLs- 4 F 7/2 and 4 F 9/2 ), and their combination were examined. Additionally, the luminescent stability of the samples under constant NIR excitation using different density power at three different temperatures was carried out. The obtained values of absolute sensitivity (0.003 K -1 -glass, 0.0019 K -1 -glass fiber 2 H 11/2 → 4 S 3/2 transition) and relative sensitivity (2.05% K -1 -glass, 1.64% K -1 -glass fiber 4 F 7/2 → 4 F 9/2 transition), as well as high repeatability of the signal, indicate that this material could be used in temperature sensing applications.

Nanophosphors are widely used, especially in biological applications in the first and second biological windows. Currently, nanophosphors doped with lanthanide ions (Ln 3+ ) are attracting much attention. However, doping the matrix with lanthanide ions is associated with a narrow luminescence bandwidth. This paper describes the structural and luminescence properties of co-doped LaPO 4 nanophosphors, fabricated by the co-precipitation method. X-ray structural analysis, scanning electron microscope measurements with EDS analysis, and luminescence measurements (excitation 395 nm) of LaPO 4 :Eu 3+ /Nd 3+ and LaPO 4 :Eu 3+ /Nd 3+ /Yb 3+ nanophosphors were made and energy transfer between rare-earth ions was investigated. Tests performed confirmed the crystal structure of the produced phosphors and deposition of rare-earth ions in the structure of LaPO 4 nanocrystals. In the range of the first biological window (650-950 nm), strong luminescence bands at the wavelengths of 687 nm and 698 nm ( 5 D 0 → 7 F 4 :Eu 3+ ) and 867 nm, 873 nm, 889 nm, 896 nm, and 907 nm ( 4 F 3/2 → 4 I 9/2 :Nd 3+ ) were observed. At 980 nm, 991 nm, 1033 nm ( 2 F 5/2 → 2 F 7/2 :Yb 3+ ) and 1048 nm, 1060 nm, 1073 nm, and 1080 nm ( 4 F 3/2 → 4 I 9/2 :Nd 3+ ), strong bands of luminescence were visible in the 950 nm-1100 nm range, demonstrating that energy transfer took place.

The effect of BaF 2 , MgF 2 , and AlF 3 on the structural and luminescent properties of gallo-germanate glass (BGG) doped with erbium ions was investigated. A detailed analysis of infrared and Raman spectra shows that the local environment of erbium ions in the glass was influenced mainly by [GeO] 4 and [GeO] 6 units. Moreover, the highest number of non-bridging oxygens was found in the network of the BGG glass modified by MgF 2 . The 27 Al MAS NMR spectrum of BGG glass with AlF 3 suggests the presence of aluminum in tetra-, penta-, and octahedral coordination geometry. Therefore, the probability of the 4 I 13/2 → 4 I 15/2 transition of Er 3+ ions increases in the BGG + MgF 2 glass system. On the other hand, the luminescence spectra showed that the fluoride modifiers lead to an enhancement in the emission of each analyzed transition when different excitation sources are employed (808 nm and 980 nm). The analysis of energy transfer mechanisms shows that the fluoride compounds promote the emission intensity in different channels. These results represent a strong base for designing glasses with unique luminescent properties.

Glass-ceramic is semi-novel material with many applications, but it is still problematic in obtaining fibers. This paper aims to develop a new glass-ceramic material that is a compromise between crystallization, thermal stability, and optical properties required for optical fiber technology. This compromise is made possible by an alternative method with a controlled crystallization process and a suitable choice of the chemical composition of the core material. In this way, the annealing process is eliminated, and the core material adopts a glass-ceramic character with high transparency directly in the drawing process. In the experiment, low phonon antimony-germanate-silicate glass (SGS) doped with Eu 3+ ions and different concentrations of P 2 O 5 were fabricated. The glass material crystallized during the cooling process under conditions similar to the drawing processes'. Thermal stability (DSC), X-ray photo analysis (XRD), and spectroscopic were measured. Eu 3+ ions were used as spectral probes to determine the effect of P 2 O 5 on the asymmetry ratio for the selected transitions ( 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 ). From the measurements, it was observed that the material produced exhibited amorphous or glass-ceramic properties, strongly dependent on the nucleator concentration. In addition, the conducted study confirmed that europium ions co-form the EuPO 4 structure during the cooling process from 730 °C to room temperature. Moreover, the asymmetry ratio was changed from over 4 to under 1. The result obtained confirms that the developed material has properties typical of transparent glass-ceramic while maintaining high thermal stability, which will enable the fabrication of fibers with the glass-ceramic core.

Fluoroindate glasses co-doped with Pr 3+ /Er 3+ ions were synthesized and their near-infrared luminescence properties have been examined under selective excitation wavelengths. For the Pr 3+ /Er 3+ co-doped glass samples several radiative and nonradiative relaxation channels and their mechanisms are proposed under direct excitation of Pr 3+ and/or Er 3+ . The energy transfer processes between Pr 3+ and Er 3+ ions in fluoroindate glasses were identified. In particular, broadband near-infrared luminescence (FWHM = 278 nm) associated to the 1 G 4  →  3 H 5  (Pr 3+ ), 1 D 2  →  1 G 4  (Pr 3+ ) and 4 I 13/2  →  4 I 15/2  (Er 3+ ) transitions of rare earth ions in fluoroindate glass is successfully observed under direct excitation at 483 nm. Near-infrared luminescence spectra and their decays for glass samples co-doped with Pr 3+ /Er 3+ are compared to the experimental results obtained for fluoroindate glasses singly doped with rare earth ions.

Glass and ceramic materials doped with rare earth (RE) ions have gained wide interest in photonics as active materials for lasers, optical amplifiers, and luminescent sensors. The emission properties of RE-doped glasses depend on their chemical composition, but they can also be tailored by modifying the surrounding active ions. Typically, this is achieved through heat treatment (including continuous-wave and pulsed lasers) after establishing the ordering mechanisms in the particular glass-RE system. Within the known systems, silicate glasses predominate, while much less work relates to materials with lower energy phonons, which allow more efficient radiation sources to be constructed for photonic applications. In the present work, the luminescent and structural properties of germanate glasses modified with phosphate oxide doped with Eu 3+ ions were investigated. Europium dopant was used as a "spectroscopic probe" in order to analyze the luminescence spectra, which characterizes the changes in the local site symmetries of Eu 3+ ions. Based on the spectroscopic results, a strong influence of P 2 O 5 content was observed on the excitation and luminescence spectra. The luminescence study of the most intense 5 D 0 → 7 F 2 (electric dipole) transition revealed that the increase in the P 2 O 5 content leads to the linewidth reduction (from 15 nm to 10 nm) and the blue shift (~2 nm) of the emission peak. According to the crystal field theory, the introduction of P 2 O 5 into the glass structure changes the splitting number of sublevels of the 5 D 0 → 7 F 1 (magnetic dipole) transition, confirming the higher polymerization of fabricated glass. The slightly different local environment of Eu 3+ centers the results in a number of sites and causes inhomogeneous broadening of spectral lines. It was found that the local asymmetry ratio estimated by the relation of ( 5 D 0 → 7 F 2 )/( 5 D 0 → 7 F 1 ) transitions also confirms greater changes in local symmetry around Eu 3+ ions. Our results indicate that modification of germanate glass by P 2 O 5 allows control of their structural properties in order to functionalize the emissions for application as luminescent light sources and sensors.

Currently, there is a growing interest in the development of multi-colored materials based on the combination of two or more systems (organic or inorganic) as a strategy to take advantage of their combined physical or chemical properties. These multi-colored materials have found potential applications as sensors, amplifiers, and optical fibers. In this work, the physical characteristics of poly(methyl methacrylate) (PMMA) doped with Terbium(III)-tris-(2,2,6,6-tetramethyl-3,5-heptanedionate) (Tb(tmhd) 3 ) at 1.57-1.58 mmol and Rhodamine B (RhB) at different concentrations were analyzed. The emission obtained from these samples (multichromophoric samples) varied as function of RhB concentration due to an efficient energy transfer process (33-65%). The role of PMMA as inert matrix that assists in the recombination process was confirmed by FTIR and Raman spectra analysis. Moreover, an improvement in thermal resistance of the materials was observed due to the presence of the dopants during the polymerization process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019. Published by Elsevier B.V.)

An investigation of the crystallization kinetics of 45S5 Bioglass ® using differential scanning calorimetry is presented in this paper. Thermal analysis was performed using the Friedman method. The activation energy and the Avrami index were calculated. The glass samples were subjected to additional controlled heat treatment at 620 °C in order to obtain bioactive glass-ceramics with enhanced mechanical properties. X-ray powder diffraction (XRD) measurements indicated the formation of the glass-ceramic structures of three cyclosilicates: Na 4 Ca 4 (Si 6 O 18 ) or Na 6 Ca 3 (Si 6 O 18 ) or Na 16 Ca 4 (Si 12 O 36 ). Based on middle infrared region (MIR) results, it can be concluded that the crystalline phase present in the tested materials was Na 6 Ca 3 (Si 6 O 18 ) (combeite). Material was doped with Eu 3+ ions, which act as a spectroscopic probe for monitoring the structural changes in the glass matrix. The decreasing value of the fluorescence intensity radio parameter indicated symmetry around the europium ions and, thus, the arrangement of the glass structure. The bioactive properties of the examined glass-ceramics were also determined. The bioactive glass fibers doped with Eu 3+ were manufactured using two different methods. Its structural and luminescent properties were examined.