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Composite up-conversion luminescent films containing a nanocellulose and SrF2:Ho particles
摘要： The synthesis of up-conversion luminescent composite films based on a nanocellulose matrix containing Sr1-xHoxF2+x particles was proposed. The combination of sulfuric acid hydrolysis and ultrasonication allowed us to synthesize a series of stable nanocellulose dispersions from various raw materials (powdered sulphate bleached wood pulp, Blue Ribbon filter paper, and microcrystalline cellulose Avicel). The size distribution of cellulose nanoparticles in the aqueous dispersions was determined. Cellulose nanocrystals (CNC) and/or cellulose nanofibrils (CNF) dispersions were used to fabricate thin films by solution casting followed by solvent evaporation under ambient conditions. The size and shape of cellulose nanoparticles, surface morphology, crystallinity index of nanocellulose, polymerization degree, and optical properties were studied. By mixing aqueous dispersions of CNC with up-conversion Sr1-xHoxF2+x particles, homogeneous suspensions were obtained. Finally, a solution casting technique was used to prepare CNC/Sr1-xHoxF2+x and CNC/CNF/Sr1-xHoxF2+x nanocomposite films. CNC/CNF dispersions were utilized for the production of flexible, durable, transparent composite films. The synthesized nanocomposites demonstrated intense red luminescence upon Ho3+ excitation by 1912 nm laser radiation. The obtained up-conversion luminescent composite films can be considered as a promising material for photonics, in particular for near-IR laser labeling and radiation visualization, luminescent sensorics.
关键词： Nanocomposites,Up-conversion luminescent films,Cellulose nanofibrils,Cellulose nanocrystals,SrF2:Ho3+
更新于2025-09-23 15:23:52
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Upconversion luminescence of CaF2-SrF2-ErF3 single crystals upon 1.5 μm laser excitation
摘要： In present work, the spectral-luminescent properties of CaF2-SrF2-ErF3 (CaF2-SrF2:Er) single crystals were investigated. The upconversion luminescence (UCL) of CaF2-SrF2: Er in the visible and infrared spectral regions upon excitation of the 4I13/2 level Er3+ ions were studied for the first time. The absolute energy yields of the UCL upon laser excitation at 1.5 μm are determined for CaF2-SrF2:Er. The possible application of fluoride crystals for increasing the efficiency of solar cells was discussed.
关键词： upconversion luminescence,single crystals,solar cells,CaF2-SrF2-ErF3
更新于2025-09-16 10:30:52
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Heat‐driven Tailored for Eliminating Nd <sup>3+</sup> Re‐clusters in Nd <sup>3+</sup> ,Gd <sup>3+</sup> ‐codoped SrF <sub/>2</sub> Laser Ceramic
摘要： Transparent Nd3+,Gd3+-codoped SrF2 laser ceramic was fabricated by a single-crystal ceramization (SCC) technique, and the fluorescence properties were also characterized. The results indicated that the SCC process would lead to reducing fluorescence properties of ceramic by re-clustering small amount of Nd3+ ions. In this paper, the re-clustering of Nd3+ ions were addressed by a simple thermal drive induced grains regrowth (TDIGR) treatment. The properties of the Nd3+,Gd3+-codoped SrF2 laser ceramic undergo the TDIGR were improved and close to precursor single crystal. Meanwhile, the transmittance of ceramic (Taverage@300-1400nm~92%) was hardly affected by the TDIGR treatment. Therefore, we have reason to believe that the combination of SCC and TDIGR is a suitable approach to obtain high optical quality neodymium, buffer ion-codoped alkaline-earth fluoride (Nd3+,B3+-codoped MF2) laser ceramics.
关键词： TDIGR,Nd3+,Gd3+-codoped SrF2,SCC,laser ceramics
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Nd,Gd:SrF <sub/>2</sub> Laser Generating 600 fs Pulses at 0.9 W of Pump Power
摘要： Fluoride crystals (CaF2, SrF2) doped with neodymium Nd3+ and codoped with non-active ions as Y3+, La3+, or Gd3+ for breaking clusters of active ions, have become recently interesting active media for the diode-pumped mode-locked lasers. They possess broader emission spectra as well as longer fluorescence lifetime in comparison with widely used crystals such as Nd:YAG or Nd:YVO4. The femtosecond Nd,Y:SrF2 laser generating 97 fs pulses was reported in the Ti:sapphire pumped system [1]. We have reported continuously mode-locked operation of this laser pumped by a 2 W multimode laser diode and mode-locked using a semiconductor saturable absorber generating pulses with the duration of 258 fs [2]. In laser systems with La3+ codoped crystals, which have wider tunability than Y3+ codoped crystals, passively mode-locked 354 to 1200 fs and continuous-wave 1044 to 1081 nm tunable operation was reported in the system pumped by 4 W laser diode [3]. Recently a new Nd,Gd:SrF2 crystal has been investigated and the dual wavelength mode-locked picosecond operation was reported for pump power higher than 3.8 W [4]. We reported femtosecond operation of laser with this crystal and obtained pulses as short as 228 fs with output power of 2 x 50 mW in system pumped by 2 W laser diode for absorbed pump power of 1320 mW [5]. In the present contribution we report on operation of this novel laser with a Brewster cut crystal in passively mode locked regime for extremely low pump power. Laser system schematic is similar as in ref. [5] and is shown in Fig. 1. A 5 mm long Brewster cut 0.5%Nd, 5%Gd:SrF2 crystal was pumped by a multimode 2 W laser diode at 796 nm and passively mode-locked using a semiconductor saturable absorber mirror (SAM). Using a chirped mirror M3 with GDD equal to -650 fs2 it was possible to achieve continuously mode locked regime at absorbed pump power of only 320 mW, with output power of 2 x 12 mW behind the mirror M4 in linearly polarized beams with nearly Gaussian spatial profile and pulse duration of 740 fs (assuming sech2 pulse shape). For higher absorbed pump power of 632 mW (905 mW incident on the crystal) the total output power of 2 x 20 mW was achieved with a pulse duration of 600 fs. The autocorrelation curve is shown in Fig. 2 together with the measured spectrum 3.3 nm wide, and centered at 1051.5 nm. The absorbed pump power is 2 - 4 times smaller in comparison with our previous results. The calculated time-bandwidth product of 0.536 gives potential to get shorter pulses (down to 352 fs) with optimum GVD compensation.
关键词： diode-pumped,semiconductor saturable absorber mirror,femtosecond pulses,Nd,Gd:SrF2,mode-locked lasers
更新于2025-09-12 10:27:22