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Physical properties of cerium doped-yttrium iron garnet ultrathin films for photovoltaic application
摘要： In this study, cerium incorporated yttrium iron garnet ultrathin films (CexY3-xFe5O12) (where x = 0, 0.1, 0.3, and 0.5) were prepared by the sol-gel method, spin coating technique, and heat treatment on quartz substrates. The effect of Ce on structural properties, morphology of thin films surface, and optical properties was explored by X-ray diffraction (XRD), field emission microscopy (FESEM), and atomic force microscopy (AFM). According to the XRD results, the films were crystalline with the cubic phase, while the FESEM indicated the YIG nanoparticles with approximately spherical shapes. The growth process of crystallite in YIG nanoparticles was investigated by X-ray peak broadening. The Williamson-Hall (W–H) analysis was utilized to maintain the contributions of crystallite size on the peak broadening of Ce:YIG nanoparticles. The structural features of thin films such as strain and stress for all of the peaks of XRD were accurately determined from the uniform deformation model (UDM) according to the YIG cubic phase. According to the AFM pictures, it seemed that thin films had a continuous and smooth surface. The absorption and transmission were measured in the visible and infrared region from 400 to 1200 nm.
关键词： Structural features,Cerium yttrium iron garnet thin films,Photovoltaic application,Optical properties,Sol-gel
更新于2025-09-12 10:27:22
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Double-Lattice Magnetoplasmonic Structures Based on BIG and Perforated Gold Films
摘要： A method of manufacturing double-lattice magnetoplasmonic crystals with the structure (Au/BIG)2, in which the plasmon gold lattices are displaced relative to each other by half a period, has been presented. Gold films with thicknesses of about 40 nm have been formed by the ion-beam sputtering–deposition method, while the adhesive properties of the films allow the dimensional etching by a sharp-focused ion beam. It has been shown that the formation of the second plasmon lattice located on top of the 100 nm thick garnet layer allows the preserving of the periodicity of the first Au lattice. However, there is a significant influence of diffusion spreading on the lower lattice material, which leads to a decrease in its density. The dependence of the intensity magnetooptical effect in the geometry on the transmission as a function of the thickness of the upper lattice and presence of an additional layer of Ta2O5 has been studied.
关键词： polycrystalline ferrite-garnet,magnetoplasmonic crystals,magnetooptical effects,deposition,ion-beam methods,sputtering,plasmon resonance
更新于2025-09-11 14:15:04
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Insight into a Novel Garnet-based Yellowish-green Phosphor: Structure, Luminescence Properties and Application for Warm White Light-emitting Diodes
摘要： White light-emitting diodes (WLEDs) have been considered as the next generation lighting technology due to its advantages such as high efficiency and environmental friendliness. However, current mainstream WLEDs, which is based on blue chip and Y3Al5O12:Ce3+ yellow phosphor, suffer from the problem of low color rendering index (CRI). To solve this problem, a yellowish-green phosphor Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ (CYAS:Ce3+) based on garnet structure has been designed in this study. The crystal structure, band structure, luminescence properties have been investigated in detail. The CYAS:Ce3+ exhibits efficient and thermal-stable yellowish-green emission. The 5d centroid shift and crystal splitting of Ce3+ ion in CYAS has been analyzed together with the structure. Moreover, good warm white light with low correlated color temperature (3210 K),high color render index (85.1) and luminous efficacy (88.5 lm/W) has been obtained by combing the CYAS:Ce3+, red phosphor CaAlSiN3:Eu2+ with blue LED chip.
关键词： Garnet,WLED,Luminescence,Phosphor
更新于2025-09-11 14:15:04
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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) - Growth, Spectroscopy and Laser Operation of Tm,Ho:CNGG: A Promising Disordered Crystal for Mode-Locked Lasers
摘要： Mode-locked (ML) lasers emitting in the spectral range of ~2 μm are based on Thulium (Tm3+) or Holmium (Ho3+) ions. The former one typically emits slightly below 2 μm where the atmosphere water vapour absorption can constrain the emission bandwidth of a ML laser. A disordered host material can provide inhomogeneous broadening of the emission spectra beyond 2 μm: recently, a Tm3+-doped disordered CNGG-type garnet generated 78 fs pulses at 2017 nm [1]. Another route is the use of Tm3+,Ho3+ codoped materials for further spectral broadening. Here, we report on the growth, structure, spectroscopic characterization, and free-running and wavelength-tunable laser operation of a Tm,Ho:CNGG disordered garnet crystal with high potential for sub-100 fs ML lasers. The crystal was grown by the Czochralski method, doped with 2.64 at.% Tm and 0.55 at.% Ho as determined by ICP-MS. The crystal structure was studied by XRD, Fig. 1(a), and Raman spectroscopy. The crystal showed a broadband emission at ~2 μm and the “effective” gain cross-section spectra were smooth and broad, Fig. 1(b). The maximum σSE for Ho3+ is 0.47×10-20 cm2 at 2080 nm. The parameters of the Tm3+→Ho3+ energy-transfer (ET) were determined as P28 (Tm → Ho) = 5.92 and P71 (Ho→Tm) = 0.68 [10-23 cm3/μs] (κET = P71/P28 = 0.115). CW (free-running) laser operation was achieved under diode-pumping at 802 nm, Fig. 2(a,b). The Tm,Ho:CNGG laser with a compact plano-plano cavity generated a maximum output power of 413 mW at 2088.3 nm with a slope efficiency η of 15.9% (vs. the absorbed pump power) and the laser threshold was at 0.36 W (for a 1.5% transmission output coupler). By placing a 6.0 mm-thick AR-coated Tm,Ho:CNGG crystal in an X-shaped cavity with Ti:Sapphire laser pumping, Fig. 2(c), wavelength-tuning of the laser emission was studied with a Lyot filter. For a 0.5% transmission output coupler, the laser wavelength was continuously tuned from 1932.5 to 2142.1 nm (a tuning range of 209.6 nm). These results indicate the suitability of Tm,Ho:CNGG disordered garnet for sub-100 fs ML and broadly tunable lasers at ~2 μm.
关键词： disordered garnet,Tm,laser operation,Ho:CNGG,spectroscopy,mode-locked lasers
更新于2025-09-11 14:15:04
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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) - Temperature Dependence of Magnetic Permeability and Optical Polarization Rotation of Gallium-Terbium Garnet Crystals
摘要： Faraday isolators (IF) are widely used in high-power fiber lasers in order to eliminate the detrimental influence of back reflections during the laser operation. One of the most widespread materials used for IF is a gallium-terbium garnet (TGG) crystal due to its appropriate magneto-optical properties. However, heating of magneto-optical crystals due to absorption of laser radiation deteriorates IF properties. Non-uniform heating leads to mechanical stresses and, therefore, to non-uniform polarization distortions. Values of optical absorption coefficients of TGG greatly depend on a crystal growth technology. Determination of the temperature dependence of optical absorption of TGG crystal was also one of the goals of this research. Optical absorption coefficient of cylindrical TGG sample (diameter d = 0.4 cm, length l = 2 cm) at 1060 nm wavelength was measured using laser calorimetry, i.e. by measuring the temperature of the crystal heated by transmitting laser radiation. Dependence of the crystal heating on transmitted optical power was 1.1±0.1 K/W. Absorption coefficient was calculated by solving the heat balance equation. Its value has increased from 1.6*10-3 cm-1 to 1.9*10-3 cm-1 as a result of heating from 22 oC to 43 oC. Also the contribution of the temperature dependent magnetic permeability μ(T) of TGG on the polarization rotation angle β was experimentally estimated. Temperature dependence of the magnetic permeability of TGG crystal was experimentally measured using resonant impedance spectroscopy. The value of TGG magnetic permeability was about 1.008 at room temperature (20 oC) and has decreased by Δμ = ? 1.2*10-4 when the crystal was heated to 80 oC. The temperature dependences of the polarization axis rotation angle change Δβ were measured in the cases of the uniform heating of TGG sample in a furnace and its nonuniform heating by transmitting linearly polarized laser radiation up to 30 W of optical power (1064 nm wavelength, 2 mm beam diameter). Applied magnetic field strength was 0,4 T, full angle of polarization axis rotation – 17,5 deg. Taking into account the measurement errors Δβ(T) ? (5 ± 0.25)*10-2 deg/ oC for both cases. It should be noticed that narrower laser beams can lead to greater differences due to the presence of larger temperature gradients. Consideration of the measurement results of μ(T) and β(T) revealed that the contribution of magnetic permeability variation with temperature to an overall polarization rotation angle change is almost 90 times lower than the thermally induced change of Verdet constant. Nevertheless, μ(T) influence should be considered if a precise control of polarization axis angle is required.
关键词： gallium-terbium garnet,Faraday isolators,TGG,magnetic permeability,temperature dependence,optical polarization rotation
更新于2025-09-11 14:15:04
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Efficacy of erbium-doped yttrium aluminum garnet laser with casein phosphopeptide amorphous calcium phosphate with and without fluoride for remineralization of white spot lesions around orthodontic brackets
摘要： Objective: This study aimed to assess the efficacy of erbium?doped yttrium aluminum garnet (Er:YAG) laser, pastes containing casein phosphopeptide amorphous calcium phosphate (CPP?ACP) with and without fluoride and their combination for prevention of white spot lesions in the enamel. Materials and Methods: This in vitro experimental study was conducted on 90 extracted sound premolars. The teeth were then randomly divided into six groups of 15: (1) Control, (2) laser, (3) CPP?ACP with fluoride (GC MI Paste, Recaldent? 900 ppm as NaF), (4) CPP?ACP without fluoride (GC Tooth Mousse Recaldent?), (5) laser + CPP?ACP with fluoride, and (6) laser + CPP?ACP without fluoride. In each group, enamel surface was exposed to the remineralizing agent. The teeth were then subjected to pH cycling for 14 days. The teeth were then sectioned, polished, and underwent cross?sectional microhardness testing at 20–160 μ depth quantitatively. Using the Simpson’s rule, the amount of mineral loss was calculated in each group. Statistical Analysis Used: ANOVA was used for the comparisons, and Tukey’s test was applied for pairwise comparisons. Results: The highest mean volume percentage of microhardness at 20–60 μ depth belonged to the group laser + CPP?ACP with fluoride and the lowest belonged to the control group (P = 0.001). The differences were not significant at 80?120 μ depth (P > 0.05). These finding are confirmed according to ?Z (mineral loss). Conclusion: Based on these results, Er: YAG laser was able to decrease demineralization and was a potential alternative to preventive dentistry and was more effective when combined with CPP?ACP products.
关键词： Casein phosphopeptide amorphous calcium phosphate,white spot lesion,erbium-doped yttrium aluminum garnet laser
更新于2025-09-11 14:15:04
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Observation of Longitudinal Spin Seebeck Voltage in YIG Films Chemically Prepared by Co-Precipitation and Spin Coating
摘要： Longitudinal spin Seebeck effect (LSSE) of Y3Fe5O12 (YIG) thin films chemically prepared on a Si substrate with a SiO2 surface layer has been investigated with a particular focus on its dependence on the metal (Pt or W) for the capping layer used to carry out the measurements. The YIG films are prepared by a combination of co-precipitation, spin coating, and annealing processes. The structural characterization by X-ray diffraction proves that the films are polycrystalline in a garnet phase with an average crystallite size of ～34 nm. The microstructural analyses of the film surface by scanning electron microscopy and scanning probe microscopy show that the roughness Ra of the film is ～31 nm. The magnetic easy axis of the YIG films is in the direction parallel to the films. We have found that the polarity of the LSSE voltage VLSSE measured with a Pt capping layer apparently differs from that observed when a W capping layer is used. The value of VLSSE increases almost linearly with increasing temperature difference (cid:2)T independent of the choice of metal for the capping layer. The observed LSSE for the polycrystalline YIG films is one order of magnitude smaller than that reported for YIG and Bi:YIG single-crystal samples grown by metal–organic decomposition.
关键词： Co-precipitation,spin coating,garnet ferrite,spin Seebeck effect (SSE)
更新于2025-09-11 14:15:04
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O12 scintillator
摘要： The characteristics of a Gd3Al2Ga3O12 crystal scintillator doped with cerium and co-doped with magnesium and titanium have been studied, mainly in view of using it for the Phase II upgrade of the LHCb electromagnetic calorimeter. Samples of the scintillator were irradiated with γ (60Co) to 2 kGy and with 24 GeV protons to 900 kGy. The proton fluence value was ～3·1015 cm?2. It was found that γ-irradiation did not produce any change in the optical transmission of the crystals in the spectral range of the scintillation light, whereas a degradation after the proton irradiation was measurable. For the 1 cm thick sample, a loss of transmission of 3.6% was measured at the wavelength of maximum scintillation (520 nm), and the measured induced absorption coefficient at this wavelength was ～3.6 m?1. The formation of radioisotopes in the crystal at proton irradiation has been analyzed. The formation of isotopes was also simulated with the help of the FLUKA package. The simulation was found to be in a good agreement with experimental results. The results have been used to estimate the expected intensity of parasitic radio-luminescence at high-luminosity operation in a GAGG/W sampling electromagnetic calorimeter.
关键词： Electromagnetic calorimetry,radiation damage,gadolinium-aluminum-gallium garnet,optical transmission,scintillation crystal
更新于2025-09-09 09:28:46
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Ultrafast Multilevel Switching in Au/YIG/n-Si RRAM
摘要： Resistive random access memory (RRAM) with ultrafast and multilevel switching is extremely promising for next-generation nonvolatile memory. Here, ultrafast unipolar resistive switchings (≈540 ps) with high off/on resistance ratio (≈104) are obtained in yttrium iron garnet Y3Fe5O12 (YIG)-based resistive memory on n-Si substrate. The sub-nanosecond operation is also successfully performed up to 85 °C with an off/on resistance ratio of ≈103. In addition, by using different compliance currents for the set process, five discrete resistance levels with ultrafast switchings among them are achieved and the multilevel states show reliable retention (>104 s). The large, stable, reproducible, and reliable switching behaviors of the Au/YIG/n-Si RRAM cell shows its great potential for ultrafast multilevel memory applications.
关键词： yttrium iron garnet (YIG),unipolar resistance switching,multistates,fast switching
更新于2025-09-09 09:28:46
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Latent tracks in bulk yttrium-iron garnet crystals irradiated with low and high velocity krypton and xenon ions
摘要： Bulk yttrium-iron garnet (YIG) single crystals have been irradiated with swift Kr and Xe ions having energies from 0.4 to 22.8 MeV/u and electronic stopping powers from 8.9 to 28.9 keV/nm near the irradiated surface. Transmission electron microscopy (TEM) has been used for direct observation of non-overlapping amorphous latent tracks in the near surface region of the irradiated bulk YIG crystals. The amorphous track radii observed in this work have been compared with previously reported data from direct and indirect measurements. It was found that the thickness of the sample subjected to swift heavy ion irradiation does not significantly affect the resulting amorphous track size observed by TEM in YIG. The results also support previously observed consistency between direct TEM and indirect Rutherford backscattering in channelling mode (RBS/C) and Mossbauer spectroscopy (MS) methods for amorphous track evaluation in YIG when electronic stopping power is greater than ～13 keV/nm, which is sufficient to create cylindrical amorphous tracks by high velocity ions (E > 10 MeV/u). Indirect methods provide underestimated values compared to TEM when the electronic stopping power is below ～13 keV/nm, for which discrete amorphous tracks are supposed to be formed by high velocity ions.
关键词： Transmission electron microscopy,Latent tracks,Radiation damage,Yttrium-iron garnet,Swift heavy ions
更新于2025-09-09 09:28:46