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Issue 1 ， 2021
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Long-lasting Phosphorescence in Nb5+ and Sm3+ Codoped YTaO4
Abstract：The Y0.98Sm0.02TaO4 long lasting phosphorescence(LLP) material was synthesized by high temperature solid state reaction, and the co-doping experiment of replacing Ta5+ with Nb5+ was also carried out. The results of X-ray powder diffraction spectra shown that the doped ions did not change the crystal structure of YTaO4. Through room temperature steady-state photoluminescence(PL) and long-lasting phosphorescence experiments, it is found that the addition of Nb5+ can greatly increase the intensity of long-lasting phosphorescence of Sm3+ in YTaO4 and change the emission color of PL and LLP. In this paper, the properties and mechanism of PL and LLP of YTaO4:Sm3+, Nb5+ are studied, respectively.Keywords：Transition metal composite oxide;long-lasting phosphorescence;Nb5+;Ta5+;color tunable- 807
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Published：2021-01-12
Cover Story
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Research Progress of Solar Directly Pumped Solid-state Laser
Abstract：Solar directly pumped solid-state laser has advantages of energy saving and high efficiency, compared with that of conventional LD pumped laser. It has great application potential in the fields of atmospheric sensing, deep space communication and national defense security, which presents great strategic significance. In this study, the domestic and abroad research progress of sunlight collecting optical system, laser gain medium and pump system design of solar directly pumped solid-state lasers was reviewed. The inter relationship between the improvement of laser quality and optical conversion efficiency was revealed. This study indicated that high convergence efficiency and high-power laser output were the core research objectives in the development of solar directly pumped solid-state laser, and the fabrication of high-quality laser gain medium was the key to realize the above goals. Finally, the development trend of solar directly pumped solid-state laser was prospected.Keywords：direct solar pumping;solid-state laser;sunlight collecting optical system;gain medium;pump system- 714
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Published：2021-01-12
Invited Review
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Effects of Trace MgO Addition on Optical and Scintillation Properties of GAGG:Ce Crystal
Abstract：Ions' co-doping is one of the important means to optimize crystals' scintillation properties. In this work, GAGG:Ce and GAGG:Ce, 0.1%Mg crystals were grown by Czochralski method. The effects of trace MgO on the optical and scintillation properties of GAGG:Ce were studied by measuring hardness, transmittance, X-ray excited luminescence(XEL) spectrum and time resolution. The average Vickers hardness of GAGG:Ce and GAGG:Ce, Mg is 1 430 kg/mm2 and 1 420.4 kg/mm2 respectively, which indicates that Mg2+ doping has little effect on the hardness of GAGG:Ce. Photoluminescence(PL) and XEL spectra show that the emission peak wavelength of GAGG:Ce and GAGG:Ce, Mg crystals is~540 nm. By Gaussian fitting the XEL spectrum, the emission peaks of 5d1→2F5/2 and 5d1→2F7/2 of GAGG:Ce, Mg are red-shifted 12~24 nm relative to GAGG:Ce, and the introduction of Mg2+ may change the transition probability distribution of Ce3+ from 5d1 excited state to2F5/2 and2F7/2. The light yields of GAGG:Ce and GAGG:Ce, Mg are 5.8×108 lx/MeV(58 000 ph/MeV) and 4.15×108 lx/MeV(41 500 ph/MeV), respectively, but the coincidence time resolution of GAGG:Ce, Mg is significantly improved, up to 146 ps. In addition, comparing the light yield of samples of different sizes, the self-absorption degree of GAGG:Ce, Mg for scintillation luminescence is less than that of GAGG:Ce. The above results indicate that trace MgO doping is an effective way to improve the scintillation performance of GAGG:Ce crystals.Keywords：gallium aluminum gadolinium garnet;co-doping;light yield;time resolution;scintillation property- 260
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Published：2021-01-12 -
Luminescence Properties of Tm3+/Ho3+ Doped BaF2 Nanocrystalline Fluorosilicate Glass Ceramics at 2.0 μm
Abstract：2.0 μm band mid-infrared lasers have attracted more and more attention due to their applications in human eye safety, photoelectric detection, and generation of mid-infrared supercontinuum. In this paper, Tm3+ ion doped and Ho3+/Tm3+ co-doped 85SiO2-7.5KF-7.5BaF2(SKB) glass containing BaF2 nanocrystalline were prepared by melt-quenching method. The Raman spectrum, absorption spectrum and mid-infrared fluorescence performances of the samples at 2.0 μm exited by 808 nm laser diode were studied. The optimal doping concentration of Ho3+/Tm3+ was obtained during the experiment. The measured fluorescence spectra manifest that the maximal emission intensity of Ho3+:5I7→5I8 at 2.0 μm can be achieved at the concentration of 1.0% Ho2O3 and 1.0% Tm2O3 in this component glass. Besides, the energy transfer mechanisms between Ho3+ and Tm3+ were also analyzed and discussed in detail. The results show that Tm3+/Ho3+ co-doped SiO2-KF-BaF2 glass ceramics can be used as the gain matrix for 2.0 μm band mid-infrared solid-state laser.Keywords：silicate glass;rare earth ion doped;2.0 μm fluorescence;BaF2;mid-infrared emission- 228
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Published：2021-01-12 -
Color-tunable Fluorescent Ink Based on Single Benzene Fluorophore
Abstract：The single benzene fluorophore dibutyl-2, 5-diaminoterephthalate 2a was synthesized by claisen condensation of dibutyl succinate followed by amination and aromatization. The maximum emission peaks of compound2a are ranged from 514 nm in n-Hexane to 574 nm in glycol, spanning 60 nm. Compound 2a displays efficient yellow emissions in solid-state(the emission maxima λem=558 nm, fluorescence quantum yield Φ=0.28). The acylation of amino group in compound 2a by 2, 2, 2-Trichloroethyl chloroformate(TrocCl) was led tomonoamide compound 2b, which gives green emissions in solid-state(λem=493 nm, Φ=0.13); and further acylation led to diamide compound 2c which gives blue emissions in solid-state(λem=467 nm, Φ=0.79). Those trichromatic fluorescent transformation also can be achieved on unbleached papers. As a result of the acylation of compound 2a on paper, the emission color can be changed from yellow to green and blue after writing different concentration of colorless TrocCl solution on the top of fluorescent 2a characters, which makes it possible to apply widely as color-tunable fluorescent ink.Keywords：Solid-state fluorescence;Colour-tunable;Diaminoterephthalate;solvatochromism- 279
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Synthesis of Nitrogen and Phosphorus Doped Carbon Dots and Their Application in Pd2+ Sensing
Abstract：The high fluorescence quantum yield(67.53%) nitrogen and phosphorus-doped carbon dots(N, P-CDs) were synthesized by hydrothermal method using m-phenylenediamine and phosphoric acid as the main raw materials and the synthesis conditions(reaction time and temperature) have been optimized. The structure and optical properties of N, P-CDs were characterized by FT-IR, ultraviolet absorption spectroscopy, fluorescence spectroscopy, and X-ray photoelectron spectroscopy, and their morphology was observed by transmission electron microscopy. The results show that N, P-CDs are spherical, with an average particle size of about 7.5 nm, and emit bright green fluorescence under 365 nm ultraviolet light excitation. The maximum excitation and emission wavelengths are 442 nm and 515 nm, respectively. The application of N, P-CDs to the detection of metal ions indicated that they displayed good selectivity to Pd2+, and the detection limit is 0.995 μmol/L. The fluorescence quenching mechanism of Pd2+ on N, P-CDs was studied by UV absorption spectroscopy and fluorescence lifetime measurement. The results showed that the quenching mechanism was static quenching, which is due to the formation of complexes between Pd2+ and N, P-CDs.Keywords：M-phenylenediamine;fluorescent carbon dots;ion detection;Pd2+ sensor- 237
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Published：2021-01-12 -
Size Effect and Luminescence Properties of MAPbBr3 and MAPbBr3/(OA)2PbBr4 Core-shell Materials
Abstract：The methylamine lead bromide MAPbBr3 and MAPbBr3/(OA)2PbBr4(octylamine lead bromide) of core-shell structure nanoparticles(NPs) were synthesized by ligand-assisted co-precipitation method, and three different sizes NPs were obtained by ultra-high-speed centrifugation, respectively. Then, their morphology and photoluminescence(PL) properties were characterized. The UV-Vis absorption and room temperature PL spectra show that MAPbBr3 and core-shell MAPbBr3/(OA)2PbBr4 NPs both exhibit a significant size-dependent band gap blue shift due to the quantum confinement effect. The low-temperature PL spectra indicate that the shell layer could suppress the phase transition of internal MAPbBr3, and the phonon energy increases with the increasing size. However, compared with MAPbBr3, the phonon energy of the core-shell MAPbBr3 NPs is smaller. The time-resolved PL measurements reveal that the PL decay of MAPbBr3 NPs is dual exponential, and the short lifetime and long lifetime increase from 1.18 ns to 1.55 ns and from 4.49 ns to 9.63 ns with the size increasing, respectively. However, the PL decay of core-shell MAPbBr3/(OA)2PbBr4 NPs is single exponential because the surfaces defects of core were strong passivated by the shell layer, and the long lifetime increases from 7.34 ns to 17.36 ns with the size increasing. The research of the PL properties of MAPbBr3 NPs has important guiding significance to improve the stability and realize high-performance devices.Keywords：perovskites;size effect;core-shell structure;luminescent properties- 184
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Published：2021-01-12 -
Synthesis, Characterization of Silicon Quantum Dots and High Sensitivity Sensing for Cu2+
Abstract：In this study, silicon quantum dots(Si-QDs) with good luminous stability and water solubility were synthesized by one-pot solvent-free method and characterized by the transmission electron microscopy(TEM), infrared spectroscopy(IR), X-ray photoelectron spectroscopy(XPS), X-ray diffraction(XRD) and fluorescence spectroscopy. It was found in the experiment that the Si-QDs emit broadband luminescence at 478 nm under the excitation at 378 nm. The luminescence of Si-QDs can be quenched statically by adding Cu2+ in aqueous solution. The stable correlation between the degree of quenching of fluorescence signal and the concentrations of Cu2+ was used to realize the quantitative detection of Cu2+. Under the optimized conditions, there was a stable correlation between the fluorescence intensity change of Si-QDs and the concentrations of Cu2+ in the range of 16.7-1 670 nmol·L-1, (F0-F)/F0=0.18808lnC(Cu2+)-0.41377(R2=0.998), and the detection limit was down to 4.7 nmol·L-1(S/N=3). Several actual water samples were detected, the recovery rates ranged from 89.47% to 106.75%. The Si-QD prepared in this study had good repeatability and stability for the rapid and highly sensitive detection of Cu2+ in water.Keywords：Silicon quantum dots;Fluorescence sensing material;copper ions;Water- 245
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Published：2021-01-12 -
Tunable Photoluminescence Properties and Energy Transfer of Ba3YB9O18:Tb3+, Eu3+ Phosphors
Abstract：A series of Ba3YB9O18:Tb3+, Eu3+ phosphors with tunable photoluminescence were successfully prepared by solid state reaction. X-ray diffraction(XRD) and transmission electron microscopy(TEM) were utilized to investigate the phase purity and crystal structure of the as-obtained phosphors. The XRD refinement results demonstrate that the linear structural evolution of Ba3YB9O18:Tb3+, Eu3+ solid-solutions obeys excellent Vegard's rule when Y3+ were substituted by Eu3+ ions. Moreover, the energy transfer process from Tb3+ to Eu3+ in Ba3YB9O18:Tb3+, Eu3+ phosphors was verified by emission spectra and decay curves. The energy transfer mechanism from Tb3+ to Eu3+ was proved to be the electric dipole-dipole interaction. Due to the energy transfer process from Tb3+ to Eu3+, the color tones can be gradually adjusted from green to red with increasing Eu3+ doping content. These results manifest that the as-synthesized Ba3YB9O18:Tb3+, Eu3+ phosphors may find potential applications for UV excited solid state lighting.Keywords：Ba3YB9O18;photoluminescence;energy transfer;phosphors- 222
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Published：2021-01-12 -
Upconversion Luminescence and Temperature Sensing Properties for Sc2(WO4)3:Er3+/Yb3+
Abstract：A series of upconversion materials Er3+/Yb3+ co-doped Sc2(WO4)3 have been prepared by a high-temperature solid-phase method. Under the 980 nm near-infrared laser, the green emission intensity of the up-conversion luminescence is greater than that of the red, and the green light is visible to the naked eyes. When 0.05% Er3+ and 0.1%Yb3+ are doped, the green emission is 27 times more than the red emission. Furthermore, the fluorescence intensity ratio method was used to describe the optical temperature sensor with two thermal coupling energy levels of Er3+ in the range of 303~573 K. At 393 K, the sensitivity of the sample reached the maximum 0.006 8 K-1. Compared with some reported materials, the sensitivity of Sc2(WO)3:Er3+/Yb3+ is higher and it has a better prospect in temperature measurement.Keywords：doping;Upconversion materials;luminescence;temperature sensing- 262
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Published：2021-01-12
Synthesis and Properties of Materials
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Fiber Coupling of Semiconductor Laser Based on Wedge-shaped Lens
Abstract：In fiber coupling system of diode laser bars, directivity deviation of emitters deteriorates the beam shaping seriously, thus leading to the degradation of fiber coupling efficiency. In order to solve this problem properly, in this paper, a wedge-shaped lens with calibrated angle is proposed to compensate the directivity deviation of the emitters and then improve the directivity of the laser beam and shaping effect. Both ZEMAX simulation and experiments are conducted. The results show that significant improvements of the beam shaping are obtained by using such wedge-shaped lens with calibrated angle. The beam parameter products(BPPs) calculated in the fast and slow axis are 7.25 mm·mrad and 5.05 mm·mrad respectively, and the focal spot dimension is 148 μm×135 μm(with 90% energy enclosed). After coupled the laser beams into a standard fiber with 200 μm core diameter and 0.2 numerical aperture(NA), the output power is measured to be 53 W and the electrical-to-optical conversion efficiency is 47% at the inject current of 60 A. Finally, the fiber coupling efficiency of 87% is achieved, increased by 7% compared to that of the conventional wedge-shaped lens.Keywords：diode laser bars;wedge-shaped lens;beam shaping;fiber coupling- 199
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Published：2021-01-12
Device Fabrication and Physics
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Thermal Analysis and Fiber Coupling Simulation Design of Multi-single Emitters Stacked Semiconductor Laser
Abstract：Multi-single diode laser emitters combination technology is an important method to obtain semiconductor lasers with high output power density. The difficulty of simplex packaging method and large volume restricts their application of high power and high optical quality. In this paper, a packaging structure with vertically stacked arrangement of multi-single emitters diode lasers is designed by vertically encapsulating single diode laser emitters between auxiliary heat sinks, making the device more miniaturization. This method can not only increase the heat dissipation channel of the single diode laser emitters, but also realize the improvement of output power without increasing the volume. In simulation, with ZEMAX optical design software, 3 single emitters diode lasers are coupled into a fiber with core diameter of 200 μm and NA of 0.22. The simulation results of the maximum output power of 28.6 W and the coupling efficiency of 95% were obtained.Keywords：semiconductor laser;finite element analysis;ZEMAX;heat dissipation;fiber coupling- 170
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Polarization and Spectral Simulation of Nano-LED Semi-polarized InGaN/GaN Single Quantum Well
Abstract：In this paper, the strain and the piezoelectric polarization distribution of Nano-LED semipolar InGaN/GaN single quantum well(QW) have been analyzed by COMSOL. The radiation spectrum characteristic of the quantum well has also been calculated by using finite element method(Silvaco). The simulated results indicate that the piezoelectric polarization changed significantly within 100 nm of the QW edge. Through the QW strain distribution, the stress release is more obvious at the edge of InGaN/GaN QW. But in the central of the semi-polarized plane, the strain release vanishes and the piezoelectric polarization increases. Thus, the luminous efficiency of QW decreases because of the quantum confinement Stark effect(QCSE). At the edge of semipolar InGaN/GaN QW, blue shift about 21 nm is observed at driven current of 60 mA. The simulated emission spectra of Nano-LED show that the double peak is obvious when the proportion of semi-polar QW is higher in the Nano-LED device, which can be used as a reference for the multi-spectrum Nano-LED design.Keywords：Nano-LED;Quantum well strain;polarization;Finite Element- 176
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Published：2021-01-12
Theoretical Calculation and Spectral Analysis
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Fabrication of Al2O3/PMMA Laminates and Its Barrier Performance in OLED Encapsulation
Abstract：Reliable thin film encapsulation is of great importance in the development of organic light emitting diodes(OLED). In this work, dense Al2O3 thin films were achieved using atomic layer deposition(ALD) under low temperature of 90℃, and ink-jet printing(IJP) was applied to deposit PMMA thin films on the surface of Al2O3 thin films with different resolutions in terms of dots per inch(DPI). It was found that Al2O3/PMMA laminates exhibited good barrier performance and optical transmittance. The water vapor transmission rate(WVTR) of the 3 dyads Al2O3/PMMA laminates showed WVTR of 8.34×10 -5 g/(m2·d). Besides, the optical transmittance of the thin films was higher than 95% in the visible wavelength, exhibiting good barrier and optical performances in OLED encapsulation.Keywords：thin film encapsulation;atomic layer deposition;ink-jet printing;water vapor transmission rate;OLED- 225
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Published：2021-01-12
Luminescence Industry and Technology Frontier
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