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We report in the present paper the Yb3+-doped Y2Ca3B4O12 diode-pumped laser operation in both continuous-wave (cw) and passively Q-switched modes. The differential slopes of the cw output power are in the 22%–40% range under different experimental conditions. Continuous tuning of the laser wavelength is obtained in the 1020–1057 nm range, in agreement with the broad emission spectra. In pulsed regime the repetition rate occurs up to 1.6 kHz and pulse energies of 30–75 μJ with about 40 ns duration are obtained. [ABSTRACT FROM AUTHOR]

Er3+:SrWO4 crystal of good optical quality was grown by Czochralski technique method. Polarized absorption and emission spectra of Er3+ ions in SrWO4 crystal have been investigated. The Judd-Ofelt (JO) theory was applied to the polarized absorption spectra of Er3+:SrWO4 to obtain the three JO parameters: Ω2=7.41×10-20 cm2, Ω4=0.25×10-20 cm2, and Ω6=1.71×10-20 cm2. The radiative probabilities, radiative lifetimes, and branch ratios of Er3+:SrWO4 were calculated. The stimulated emission cross sections of the potential laser transitions at 1535 nm were determined using the reciprocity method and the Fuchtbauer-Ladenberg formula, and the potential laser gain versus wavelength for the 4I13/2→4I15/2 transition has been estimated and discussed. [ABSTRACT FROM AUTHOR]

Crystal growth in China has a long history and is developing rapidly at the present time. In the past decade, significant efforts have been directed toward the research of structure−property relationships and high quality crystal growth, which has brought to fruition many fields covering nonlinear optical, laser, ferro-/piezo-electric, and wide band gap semiconductor crystals. In this contribution, selected research work accomplished by Chinese scientists in crystal engineering and growth is reviewed. Crystal growth in China has a long history and is developing rapidly at the present time. In the past decade, significant efforts have been directed toward the research of structure−property relationships and high quality crystal growth, which has brought to fruition many fields covering nonlinear optical, laser, ferro-/piezo-electric, and wide band gap semiconductor crystals. In this contribution, selected research work accomplished by Chinese scientists in crystal engineering and growth is reviewed. [ABSTRACT FROM AUTHOR]

Abstract: The single crystal of ZnWO4:Ho3+ was grown by Czochralski technique. The XRD, absorption spectra, fluorescence spectrum are presented, and the Judd–Ofelt (J–O) intensity parameters Ω 2, Ω 4, Ω 6 are obtained to be 4.61×10−20 cm2, 0.16×10−20 cm2, 0.48×10−20 cm2, respectively. Calculated radiative transition rate, branching ratios, and radiative lifetime for different transition levels of ZnWO4:Ho3+crystals are presented. The most intense line correlative with the transition 5S2 → 5I8 at 543nm is potentially used for green solid state laser, and the fluorescence lifetime of this energy level is 14.1μs. [Copyright &y& Elsevier]

Abstract: Good quality crystals ZnWO4 activated with Er3+ have been grown by means of Czochralski method and characterized using optical spectroscopy techniques. XRD, absorption spectra, fluorescence spectrum are presented and the Judd–Ofelt intensity parameters Ω 2, Ω 4, and Ω 6 are obtained to be 6.76×10–20, 0.37×10–20, and 0.50×10–20 cm2, respectively. Along crystallographic axes, refractive indices are presented. The fluorescence decay time of the 4 I 13/2 level has also been investigated and shows an exponential behavior with a lifetime value of 5.52ms. The crystal is potentially used for green and infrared eye-safe lasers. [Copyright &y& Elsevier]

Abstract: Single-crystal ZnWO4:Dy3+ was grown by Czochralski technique. The XRD, absorption spectra as well as fluorescence spectrum are investigated and the Judd–Ofelt intensity parameters Ω 2, Ω 4, Ω 6 are obtained to be 7.76×10−20 cm2, 0.57×10−20 cm2, 0.31×10−20 cm2, respectively. Calculated radiative transition rate, branching ratios and radiative lifetime for different transition levels of ZnWO4:Dy3+ crystals are presented. Fluorescence lifetime of 4F9/2 level is 158μs and quantum efficiency is 66%.The most intense fluorescence line at 575nm correlative with transition 4F9/2 → 6H13/2 is potentially for application of yellow lasers. [Copyright &y& Elsevier]

Abstract: Nd3+-doped NaLa(WO4)2 single crystal with a dimension of ∅20mm×40mm and a good optical quality was grown by Czochralski method. The polarized absorption spectra and emission spectra were measured at room temperature. The absorption cross-section and emission cross-section were presented. The Judd–Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Ω t (t =2,4,6), radiative transition rates A, radiative lifetimes τ R and fluorescent branching ratios β. The calculated radiative lifetime was compared with the experiment data for the 4F3/2 emitting level. All spectral features are strongly affected by an inhomogeneous broadening connected with the ‘disordered crystal’ character of the title compound. [Copyright &y& Elsevier]

Abstract: NaLa(WO4)2:Dy3+ crystals were grown successfully by the Czochraski technique. The Raman, infrared, electronic absorption and emission spectra were measured at room temperature. The Judd–Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Ω t (t =2, 4, 6), radiative transition rates A, radiative lifetimes τ R, and fluorescent branching ratios β. Although there are several transitions originating in the 4F9/2 level, a major part of emission intensity is contained in the 4F9/2 → 6H13/2 transition. The stimulated emission cross-sections for this transition were estimated by using the Füchtbauer–Ladenburg method. The luminescence decay curve was also measured at room temperature. The results indicate that NaLa(WO4)2:Dy3+ may be considered as laser active materials operating near 0.57μm. [Copyright &y& Elsevier]

Abstract: Yb3+ doped SrWO4 crystal has been grown by the Czochralski method. Polarized absorption and emission spectra together with fluorescent decay curve were measured at room temperature. The stimulated emission cross sections of the potential laser transitions were determined using the reciprocity method and the Fuchtbauer–Ladenberg formula. The potential laser gain versus wavelength for the 2F5/2 → 2F7/2 transition was also estimated and discussed. This material is a potential candidate for a 1.0μm laser media. [Copyright &y& Elsevier]

Abstract: Ca3Gd2(BO3)4:Er3+ crystals of high optical quality with a large size up to ∅25mm×60mm were grown by Czochralski method. The absorption spectra of the crystal in three mutually perpendicular arbitrary directions at room temperature were measured. Based on Judd–Ofelt theory and a least square fit of calculated three perpendicular directions and averaged results of the absorption line intensity (referred to as TPM method), the intensity parameters Ω t (t =2,4,6), the radiative transition rates, the radiative lifetimes, the fluorescence branching ratios, the experimental and theoretical oscillator strengths were obtained. The fluorescence spectrum and decay curve under the excitation of 530nm were presented too. The stimulated emission cross-section and radiative quantum efficiency were also diplayed. [Copyright &y& Elsevier]

Abstract: crystal with the size up to 13 mm×44 mm was grown successfully by the Czochralski technique and its optical properties were presented. The absorption cross-section and emission cross-section were presented. Also, the potential laser gain near 1.9 μm was investigated. In the framework of the Judd–Ofelt (J–O) theory, the intensity parameters were calculated to be: Ω2=11.375×10−20 cm2, Ω4=5.077×10−20 cm2 and Ω6=6.524×10−20 cm2. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetime as well as the branching ratios were calculated, too. This crystal is promising as a tunable infrared laser crystal. [Copyright &y& Elsevier]

Abstract: This paper reports the growth of Nd3+:NY(WO4)2 crystal with high optical quality and large size. Nd3+:NY(WO4)2 crystal with the dimension Φ30×75mm2 and optical homogeneity 4×10−5 was grown by Czhchoralski method: the seed used was [100] orientation, the pulling rate and rotating rate were 0.5–1.25mm/h and 15rpm, respectively. The growing processes and characteristics of Nd3+:NY(WO4)2 crystal was discussed. Its unpolarized absorption spectra and emission spectra were measured. The absorption cross-section and emission cross-section were presented. Based on the Judd–Ofelt theory, we obtained the three intensity parameters: , , and . The radiative probabilities, radiative lifetimes, branch ratios and quantum efficiency of Nd3+:NY(WO4)2 were calculated too. [Copyright &y& Elsevier]

Abstract: Tm3+:SrWO4 crystal of good optical quality with sizes of 15mm×60mm was grown successfully by Czochralski technique method. The orientation procedure of this crystal was discussed. The principal coefficients of thermal expansion along (001), (010), (100) directions were precisely measured to be 2.73×10−5, 1.00×10−5, 1.05×10−5 °C−1, respectively. Based on the Judd–Ofelt theory, we obtained the three intensity parameters: Ω 2=7.41×10−20, Ω 4=0.25×10−20, and Ω 6=1.71×10−20 cm2. The radiative probabilities, radiative life times, and branch ratios of Tm3+:SrWO4 were calculated. The room temperature polarized fluorescent spectra and fluorescent decay curve were measured. The luminescent quantum efficiency of the 3H4 level was investigated and the quantum efficiency is determined to be approximately 69.84% for this material. [Copyright &y& Elsevier]

Abstract: Pure and rare-earth (Nd3+, Tm3+ and Er3+)-doped strontium tungstates of good optical quality with sizes of about 20mm×50mm were grown successfully by the Czochralski technique. The (001) orientation was found to be the favorable direction for crystal growth. X-ray powder diffraction (XRD), differential thermal analysis (DTA) and differential scanning calorimeter (DSC) of pure strontium tungstate were measured. The concentrations of Nd3+, Tm3+ and Er3+ were measured and their segregation coefficients were also calculated. The absorption and emission spectra of rare-earth-doped crystals as a function of the and polarizations were presented and discussed. Favorable values of the absorption cross section centered at about 800nm suggest that Nd3+- and Tm3+-doped strontium tungstates are promising candidates for laser diode (LD) pumping. [Copyright &y& Elsevier]

Abstract: Nd3+ doped LaB3O6 single crystal with the size up to Φ20×35 mm was grown successfully by the Czochralski technique. The absorption and luminescence spectra of trivalent neodymium in LaB3O6 crystal were measured at room temperature. Also, room temperature luminescence decay curve in correspondence with the emission line 4F3/2→4I11/2 centered at 1062 nm was measured. In the framework of the Judd–Ofelt (J–O) theory, the intensity parameters were calculated to be: Ω2=0.54×10−20 cm2, Ω4=2.31×10−20 cm2, Ω6=6.94× 10−20 cm2. The calculated radiative probabilities, radiative branching ratios and radiative lifetime for the emissions from the 4F3/2 level of Nd3+ ions in LaB3O6 single crystal were presented. The luminescent quantum efficiency was also displayed. [Copyright &y& Elsevier]

The absorption and fluorescence spectra of Nd3+:Gd0.2Y0.766Al3(BO3)4 crystal have been measured. Basing on Judd–Ofelt and TPM theory, intensity parameters Ωt (t=2,4,6), radiative lifetime, experimental and theory oscillation strength, fluorescence branching ratios and stimulated emission cross-sections were obtained and related to the laser action of this crystal. A laser output of 48 mW at 1060 nm and of 78 mW at 1300 nm with the optical to optical efficiency of 20% and of 9.75% respectively were obtained under a Ti–sapphire laser pumping. Meanwhile, a laser output of 26.7 mW at 532 nm with an optical to optical efficiency of 10.68% was obtained when it was pumped by a AlGaAs diode laser. [Copyright &y& Elsevier]

Nd3+:LaB3O6 crystals with the size up to ∅20 mm×35 mm were grown by the Czochralski technique. The absorption spectrum was measured and its absorption peaks were assigned. The absorption cross section σa at about 799 nm was measured to be 3.37×10-20 cm2. An emission spectrum was obtained from 799 nm wavelength pumping. [Copyright &y& Elsevier]

The Ca3Gd2(BO3)4:Yb3+ crystal with a size up to ∅ 20 mm×50 mm was grown by the Czochralski method. The absorption and emission spectra were measured. There is a broad absorption band ranging from 850 to 1000 nm in the absorption spectrum. A broad emission spectrum from 930 to 1100 nm was exhibited from 895 nm wavelength pumping. This crystal is promising as a tunable infrared laser crystal. [Copyright &y& Elsevier]

The GdAl3(BO3)4:Tm3+ crystal with size up to 15 mm×15 mm×25 mm was grown from the K2O3–MoO3–B2O3 solvent system by the top seed solution growth (TSSG) method. The absorption spectrum was measured and its absorption peaks were assigned. The emission spectrum ranging from 500 to 1800 nm was obtained from 468 nm wavelength pumping. The absorption cross section σa at 800 nm was determined. [Copyright &y& Elsevier]

Pure and Nd3+-doped Cd3Y(BO3)3 crystals with sizes up to 20 mm were grown from a Li6B4O9 solvent system by using the top seeded solution growth method. The second harmonic generation coefficients of the crystals were measured to be about two times larger than that of KH2PO4 (KDP). The Absorption spectra were measured and the absorption peaks were assigned. The emission spectrum of Nd3+:Cd3Y(BO3)3 crystal was obtained under an excitation of 808 nm. [Copyright &y& Elsevier]

The Ca3Y2(BO3)4:Er3+ crystal with a size up to ϕ 20 mm×30 mm was grown by the Czochralski method. The absorption spectrum was measured and its absorption peaks were assigned to the corresponding transitions between the Er3+ energy levels. A broad emission spectrum from 1429.4 to 1662.8 nm was exhibited from 530 nm wavelength pumping. This crystal is promising as a tunable infrared laser crystal. [Copyright &y& Elsevier]

The absorption spectra of Tm3+:KGd(WO4)2 crystal in three mutually perpendicular arbitrary directions at room temperature were measured. Based on Judd–Ofelt theory and TPM method, the intensity parameters Ωt (t=2,4,6), the radiative lifetimes, the experimental and theoretical oscillation strengths, and the fluorescence branching ratios were obtained. The broad emission spectrum from 1650 to 2000 nm was obtained under 800 nm excitation. Also, the fluorescence spectra at 455 and 665 nm were measured under 360 nm excitation. Their stimulated emission cross-sections were also calculated. [Copyright &y& Elsevier]

The Tm3+:KGd (WO4)2 crystal with the size up to 50 mm was grown from the K2O–WO3–BO3 solvent system by using the top seeded solution growth method. The absorption spectrum was measured and its absorption peaks were confirmed. The emission spectra of the crystal at 455 and 665 nm were obtained when a light of 360 nm excited this crystal. A broad emission spectrum from 1650 to 2000 nm was obtained when a light of 800 nm excited this crystal. It is expected that this crystal may be useful as a tunable infrared laser crystal. [Copyright &y& Elsevier]

Abstract: The luminescence spectra of the 4F3/2 → 4I9/2 transition of Nd3+ ions in a SrWO4 crystal have been analyzed as a function of pressure at room temperature. Experiments have been performed in a diamond-anvil cell up to 13GPa. At around 10GPa some changes in the emission spectra have been observed which are attributed to a structural phase transition of the SrWO4 matrix. These results are in good agreement with a previous paper, in which in a pure SrWO4 matrix a scheelite to fergusonite phase transition is found around 10.5GPa. Moreover, with increasing pressure, the decay curves from the 4F3/2 are nonexponential and faster indicating that the energy transfer processes between Nd3+ ions are important. [Copyright &y& Elsevier]

Abstract: Single-crystal ZnWO4 doped with nickel ion has been grown by the Czochralski technique. The XRD is investigated and the absorption spectrum as well as the emission spectrum is measured. Along crystallographic axes, refractive indices are presented. In octahedral approximation, using the Tanaba–Sugano theory, crystal field split is discussed, and so the Racah parameter B and crystal field parameters 10Dq are calculated. Compared with pure ZnWO4 (∼4 eV), the band edge obtained was 3.7 eV for ZnWO4:Ni2+. [Copyright &y& Elsevier]

The authors report the passive Q switching of a diode pumped Yb:GdAl3(BO3)4 (Yb:GAB) laser. The slopes of the average output power are 25% and 39.5% under different experimental conditions. The repetition rates occur in the 1–4.5 kHz range and pulse energies of 125 and 165 μJ with about 30 ns duration are obtained. An experimental comparison with passively Q-switched Nd:GAB laser is provided. A theoretical analysis is performed. It is in reasonable agreement with the experimental data and it is shown to be a useful tool for predicting the optimization of the cavity parameters. [ABSTRACT FROM AUTHOR]

The Ca3Y2(BO3)4:Tm3+ crystal with the size up to ∅ 15 mm×35 mm was grown by the Czochralsky method. The absorption spectrum was measured and its absorption peaks were assigned to the corresponding transitions between the Tm3+ energy levels. A broad emission spectrum ranging from 1332.6 to 1429.1 nm was exhibited from 800 nm wavelength pumping. This crystal is promising as a tunable infrared laser crystal. [Copyright &y& Elsevier]

We demonstrate the simultaneous generation of the three basal red–green–blue colors from a lone GdAl[sub 3](BO[sub 3])[sub 4]:Nd[sup 3+] bi-functional laser and optical nonlinear crystal. The laser works in a dual-wavelength operation in the two [sup 4]F[sub 3/2]→[sup 4]I[sub 11/2] (near 1062 nm) and [sup 4]F[sub 3/2]→[sup 4]I[sub 13/2] (near 1338 nm) channels, under a fixed wavelength pumping (at 744.7 nm) and with a fixed crystal orientation. Red and green results from self-frequency doubling of the two laser channels, blue results of self-sum frequency mixing of the pump and the 1338 nm laser. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highlights • The first demonstrates spectroscopic and laser properties of Tm3+/Ho3+-SLGO Crystal. • The stimulated emission cross-sections are larger than YAG and YAP. • The maximum output powers of 6.15 W for a-cut crystal have been obtained. Abstract The Tm3+/Ho3+-SrLaGa 3 O 7 crystal was grown using the Czochralski (CZ) method. The absorption spectra, the fluorescence spectra around 2.0 μm and energy-transfer (ET) schemes between Tm3+ ions and Ho3+ ions has been studied. The lasing performance of Tm3+/Ho3+-SrLaGa 3 O 7 crystal for a-cut and c-cut pumped by a fiber-coupled laser diode laser are presented in this paper. The maximum output powers of 6.15 W for a-cut crystal at 2041 nm and 2.51 W for c-cut crystal at 2044 nm have been obtained, respectively. The maximum slope efficiency in terms of absorbed pump power nearly reached 36.5% for the a-cut crystal and about 18.8% for the c-cut crystal. In addition, the width of tuning can reach about 450 nm, suggesting the potential of these crystals for ultrashort pulse generation by mode-locking. [ABSTRACT FROM AUTHOR]

A 2 at.% Dy3+: CaYAlO4 single crystal was grown successfully. The electronic structures of Ca2+/Y3+ mixed sites in CaYAlO4 were investigated using first-principles based on density functional theory. The effects of Dy3+ doping on the structural parameters of host crystal were studied using XRD pattern. The optical properties including absorption spectrum, excitation spectrum, emission spectra and fluorescence decay curves were thoroughly investigated. The results show that the Dy3+: CaYAlO4 crystal could be pumped by the blue InGaN and AlGaAs or 1281 nm laser diodes. Furthermore, an intense 578 nm yellow emission was obtained directly under excitation at 453 nm, meanwhile, evident mid-infrared light emitting was observed by 808 or 1281 nm laser excitation. The fitted fluorescence lifetimes of 4F9/2 and 6H13/2 levels were about 0.316 ms and 0.038 ms, respectively. It can be concluded that this Dy3+: CaYAlO4 crystal could simultaneously act as a promising medium for both solid-state yellow and mid-infrared laser outputs. [ABSTRACT FROM AUTHOR]

A single crystal of the title compound is grown by the Czochralski method and characterized by XRD, refractive index, absorption, and fluorescence measurements to explore its potential 2 μm laser properties. [ABSTRACT FROM AUTHOR]

A Sm 3+ -doped Ca 3 La 2 (BO 3 ) 4 single crystal was grown by the Czochralski method. Its polarized absorption, emission spectra and fluorescence lifetime measurements were carried out at room temperature. Based on the Judd–Ofelt theory, the spectroscopic parameters Ω t ( t = 2, 4, 6), radiative transition probabilities, radiative lifetime and fluorescence branching ratios were obtained. The stimulated emission cross section, the fluorescence lifetime and the quantum efficiency of the promising laser transition were also calculated and compared with other reported crystals. The results showed that Sm 3+ :Ca 3 La 2 (BO 3 ) 4 is a promising candidate for the orange–yellow laser emission. [ABSTRACT FROM AUTHOR]

In the flux system of GdAl3(BO3)4, the compromise in competition between thermodynamic and kinetic control on the mass transfer has been studied from the viewpoint of chemical engineering. Different control mechanisms on the mass transfer in the melt growth system result in various mesoscale morphologies of a single crystal. Both the calculated and experimental results demonstrate thermodynamic control of the anisotropic mass transfer during crystal growth, leading to the mesoscale morphology evolution of the GdAl3(BO3)4 single crystal similar to the matryoshka. The present work can deepen our understanding of mesoscale morphology evolution of the GdAl3(BO3)4 single crystal in the flux growth system. [ABSTRACT FROM AUTHOR]

The chemical bonding theory of single crystal growth was applied to a Gd3Ga5O12 (GGG) Czochralski growth system. On the basis of anisotropic chemical bonding characteristics, the mesoscale process controlled by both thermodynamics and kinetics has been studied in GGG single crystal growth. Starting from the unit-scale in the growth system, the mesoscale structures undergo evolution from GdO8, GaO6, and GaO4 to Gd3Ga5O12 clusters and to a GGG single crystal via chemical bonding between Gd, Ga, and O. On the basis of the chemical bonding theory of single crystals, the GGG single crystal thermodynamically prefers to exhibit a hexagonal configuration along the [111] pulling direction. Kinetically, isotropic mass transfer in the Czochralski growth process leads to formation of a GGG single crystal with a circular configuration, as viewed down along the [111] direction. In such a case, the GGG single crystal maintains the lowest energy. In order to satisfy both thermodynamic and kinetic controls, the thermodynamically preferred {−110} microfacets are exposed on the microscale and the single crystal adopts a circular shape on the macroscale. The present work deepens our understanding of the mesoscale process in the GGG Czochralski growth system. [ABSTRACT FROM AUTHOR]

Highlights: [•] Yb3+:LaCa4O(BO3)3 single crystal was successful grown by the Czochralski method. [•] The polarized spectral properties were first analyzed. [•] Laser potentiality was evaluated based on our calculations. [•] Yb:LaCOB are beneficial to the tunable or Q-switching ultra-short laser pulse. [ABSTRACT FROM AUTHOR]

The growth and characterization of Cr,Nd:Y3Al5O12 (YAG) crystal are reported. By improving the synthesis and sintering processes of polycrystalline materials, as well as the temperature gradient and annealing atmosphere, a high quality crystal with size of ϕ30 mm × 110 mm is obtained by using the Czochralski technique. After measuring the concentrations of dopant Cr3+ and Nd3+ within the different parts of the grown crystal, it is found that the distribution of dopant ions is uniform throughout the crystal. The fluorescence spectra of Cr,Nd:YAG crystal exhibit intense emissions at 1064 nm under excitations of 808 and 450 nm. The fluorescence lifetime of Nd: 4F3/2 level is obtained to be 234.2 µs. The maximum average output power reaches 7.87 W with a slope efficiency of 31.2% for near‐infrared laser at 1063.9 nm. The above results indicate that Cr,Nd:YAG crystal is a promising gain media for all‐solid state lasers. [ABSTRACT FROM AUTHOR]

Abstract: Tm3+/Ho3+ co-doped NaLa(WO4)2 single crystal was successfully grown by the Czochralski method. The crystal was characterized by room temperature absorption spectra, fluorescence spectra around 2μm, up-conversion fluorescence and luminescence decay measurements. Spectroscopic properties related to the laser operation around 2μm of Ho3+ ions have been evaluated. The energy level scheme and energy transfer processes of Tm3+ and Ho3+ were analyzed. The obtained spectroscopic results show the crystal is a potentially host for Ho3+ 2μm infrared laser. [Copyright &y& Elsevier]

High optical quality Dy3+-doped CaLaGa 3 O 7 (abbreviated as Dy: CLGO below) crystal was grown successfully by the Czochralski technique along the (0 0 1) orientation. The lattice parameters of the as-grown crystal were obtained by Rietveld refinement to its XRD pattern. The electronic structures including band structure and density of state (DOS) were calculated by using first-principles calculations based on density functional theory (DFT). The spectroscopic characteristics of Dy: CLGO are investigated, with special attention to the yellow emission that could be pumped directly by the rapidly developed blue GaN LD. Based on the Judd-Ofelt (J-O) theory, the intensity parameters from the measured line strengths were determined. The J-O parameters were used to predict radiative transition probabilities, radiative lifetime and branching ratios for various excited levels of the Dy: CLGO crystal. The absorption cross-sections of Dy: CLGO at 453 nm are calculated to be 0.14 × 10−20 cm2 and 0.11 × 10−20 cm2 for π- and σ-polarizations, respectively. Meanwhile, Dy: CLGO exhibits strong yellow emission at 574 nm corresponding to the transition 4F 9/2 → 6H 13/2 with stimulated emission cross-sections of 3.88 × 10−21 cm2 and 3.42 × 10−21 cm2 for π- and σ-polarizations, respectively. The relatively long fluorescence lifetime (565 μs) indicates a high laser efficiency of the crystal. All results suggest that Dy: CLGO crystal could be a promising candidate for yellow laser at 574 nm pumped by blue GaN LD. • A new yellow laser crystal of Dy3+ doped CaLaGa 3 O 7 was grown successfully. • The first-principles calculations on the crystal are carried out. • Structure characterization and optical properties were analyzed. • The strong emission band with peak at 574 nm is observed in Dy3+: CaLaGa 3 O 7 crystal. • Dy3+: CaLaGa 3 O 7 crystal can be acted a promising candidate for yellow laser. [ABSTRACT FROM AUTHOR]

Accurate light irradiation towards phytochrome has been considered as a key method to improve the efficiency of plant cultivation. In this work, a series of far red-emitting Mn4+-activated SrGd 2 Al 2 O 7 (SGAO) phosphors were synthesized by high temperature solid-state reaction. Under excitation at 330 nm, the optimized SGAO:0.1%Mn4+ phosphor exhibits intense far-red emission in narrow range of 701–740 nm, which matches well with the absorption of phytochrome P FR and excludes from that of the phytochrome P R. Moreover, the SGAO:0.1%Mn4+ sample exhibits considerable thermal quenching of far-red emission towards temperature, the emission intensity around 719 nm at 423 K was approximately 33% of that at room temperature. Also, the crystal field strength D q , the Racah parameters B and C, and the nephelauxetic ratio β 1 of SGAO: Mn4+ were calculated and discussed. The results provide a reference for developing new high-efficient far-red-emitting phosphor towards indoor plant growth LEDs. • Narrow band far-red emission centered at 719nm can be observed in SrGd 2 Al 2 O 7 : Mn4+ phosphors under exciting at 365nm. • The emission band matches well with the absorption of phytochrome P FR and excludes from that of the phytochrome P R. • The most intense far-red emission in SrGd 2 Al 2 O 7 :Mn4+ phosphors occurs upon the situation of 0.1% Mn4+ dopant. • SrGd 2 Al 2 O 7 :Mn4+shows the potential as a light-converter in the application of plant growth LEDs. [ABSTRACT FROM AUTHOR]

The continuously increasing CO2 released from human activities poses a great threat to human survival by fluctuating global climate and disturbing carbon balance among the four reservoirs of the biosphere, earth, air, and water. Converting CO2 to value-added feedstocks via electrocatalysis of the CO2 reduction reaction (CO2RR) has been regarded as one of the most attractive routes to re-balance the carbon cycle, thanks to its multiple advantages of mild operating conditions, easy handling, tunable products and the potential of synergy with the rapidly increasing renewable energy (i.e., solar, wind). Instead of focusing on a special topic of electrocatalysts for the CO2RR that have been extensively reviewed elsewhere, we herein present a rather comprehensive review of the recent research progress, in the view of associated value-added products upon selective electrocatalytic CO2 conversion. We initially provide an overview of the history and the fundamental science regarding the electrocatalytic CO2RR, with a special introduction to the design, preparation, and performance evaluation of electrocatalysts, the factors influencing the CO2RR, and the associated theoretical calculations. Emphasis will then be given to the emerging trends of selective electrocatalytic conversion of CO2 into a variety of value-added products. The structure-performance relationship and mechanism will also be discussed and investigated. The outlooks for CO2 electrocatalysis, including the challenges and opportunities in the development of new electrocatalysts, electrolyzers, the recently rising operando fundamental studies, and the feasibility of industrial applications are finally summarized. [ABSTRACT FROM AUTHOR]

Yb3+/Tm3+: CaYAlO 4 (CYA) and Nd3+/Yb3+/Tm3+: CYA bulk single crystals were grown using the Czochralski (Cz) method. The polarized absorption, upconversion luminescence (UCL) spectra under 980 nm and 808 nm pumping, and fluorescence decay curves were measured as well as Judd-Ofelt (J-O) theory calculations were performed to investigate the sensitization effect of Yb3+ and Nd3+/Yb3+co-doping in Tm3+: CYA single crystal. Obvious enhancement was observed in Tm3+-activated crystals for the blue upconversion emission (∼474 nm) when doped with Yb3+ or co-doped with Nd3+/Yb3+. The energy transfer efficiency is 72.6% (Yb3+→Tm3+) and 71.7% (Nd3+→Yb3+/Tm3+) in Yb3+/Tm3+: CYA and Nd3+/Yb3+/Tm3+: CYA single crystals respectively. The gain cross-sections were calculated, and it can stated that the blue laser output derived from upconversion is possible around 474 nm related to the transition of 1G 4 → 3H 6 in Yb3+/Tm3+: CYA and Nd3+/Yb3+/Tm3+: CYA crystals. • The bulk single crystals of Yb3+/Tm3+: CaYAlO 4 (CYA) and Nd3+/Yb3+/Tm3+: CYA were grown by Czocharlski (CZ) method. • The upconversion fluorescence properties of Yb3+/Tm3+: CYA and Nd3+/Yb3+/Tm3+: CYA crystals under the pumping of 980 nm and 808 nm were studied specifically. • The energy transfer mechanism from Yb3+ to Tm3+ in Yb3+/Tm3+: CYA crystal and Nd3+ to Yb3+/Tm3+ in Nd3+/Yb3+/Tm3+: CYA crystal was discussed. [ABSTRACT FROM AUTHOR]

The Yb3+: CaLaGa 3 O 7 crystal with high-quality was grown successfully by the Czochralski method. The structure parameters of Yb3+: CaLaGa 3 O 7 crystal are determined by the X-ray Rietveld refinement method. The absorption and fluorescence spectra, fluorescence lifetime and laser performance parameters were investigated in detail. The large absorption cross-section (1.14 × 10−20 cm2 for π-polarization and 1.06 × 10−20 cm2 for σ-polarization) of the crystal at around 980 nm indicates that the crystal can be pumped efficiently by the commercialized InGaAs laser diode. The stimulated emission-cross section at 1004 nm was calculated to be 1.11 × 10−20 cm2 for π-polarization and 1.04 × 10−20 cm2 for σ-polarization. The above results reveal that Yb3+: CaLaGa 3 O 7 crystal can be regarded as a potential candidate for realizing tunable solid-state and ultrashort pulsed lasers with LD pumping. • Single crystal of Yb3+ codoped CaLaGa 3 O 7 was grown successfully. • Structure characterization of the crystal were analyzed. • The optical properties and laser performance parameters were investigated. • Yb3+: CaLaGa 3 O 7 crystal can be acted as a promising candidate for ultrafast pulse laser. [ABSTRACT FROM AUTHOR]

MIR emission spectra of Er3+: CLGO and Nd3+/Er3+: CLAGO crystals. • Single crystal of Nd3+/Er3+ codoped CaLaAl 0.6 Ga 2.4 O 7 was grown successfully. • The detailed spectroscopic properties and energy transfer mechanism were analyzed. • Enhanced 2.7 μm emission was achieved in Nd3+/Er3+: CaLaAl 0.6 Ga 2.4 O 7 crystal. • Nd3+/Er3+: CaLaAl 0.6 Ga 2.4 O 7 crystal can be acted as a promising candidate for MIR lasers. Nd3+/Er3+: CaLaAl 0.6 Ga 2.4 O 7 (abbr. as Nd3+/Er3+: CLAGO) crystal was firstly grown by Czochralski method. The 2.7 μm fluorescence emission properties and energy transfer mechanism of this crystal were investigated. Besides better absorption characteristic, the spectra of Nd3+/Er3+: CLAGO show much weaker near-infrared emission as well as superior mid-infrared emission in comparison to Er3+: CLGO. Furthermore, the self-termination bottleneck for Er3+ 2.7 µm laser was greatly decreased in Nd3+/Er3+: CLAGO crystal and the energy transfer efficiencies of Nd3+: 4F 3/2 → Er3+: 4I 11/2 and Er3+: 4I 13/2 → Nd3+: 4I 15/2 were determined. In the best case, the above four advantages indicate that the Nd3+/Er3+: CLAGO crystal might be suitable for pulsed operation and a promising 2.7 μm laser medium. [ABSTRACT FROM AUTHOR]

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been widely used for in situ microanalysis of elemental concentrations in solid samples, but its application is hampered by a lack of matrix-matched and homogeneous reference materials (RMs). In this work, a new method for preparing matrix-matched and homogeneous LA-ICP-MS reference materials has been developed. A multiple rare earth element (REE) doped CaWO4 single crystal (CaW-1) was successfully prepared by the Czochralski technique. The matrix composition and crystal structure were confirmed by X-ray diffraction (XRD) and electron microprobe analysis (EMPA), which indicates that these crystals have a matrix composition of CaWO4 and are matrix-matched with natural scheelite. The homogeneity of REE distribution was systematically studied by seven methods and the results demonstrated that REEs are distributed homogeneously in the CaWO4 single crystal with slight fluctuation (RSDs: ca. 4%). It can be concluded that the synthesized CaWO4 single crystal meets both crucial requirements, matrix-matched and homogeneous distribution, for an LA-ICP-MS reference material, and therefore it was used to quantitatively calibrate REE concentrations in natural scheelite. The results showed that acceptable analytical errors (<8%) were obtained, which were more desirable than those obtained with non-matrix-matched NIST SRM 610 as the RM. It robustly validates the ability of the developed method for preparing CaWO4 single crystals as possible LA-ICP-MS reference materials to calibrate REE concentrations in natural scheelite. [ABSTRACT FROM AUTHOR]

Conversing CO2 into value‐added chemicals endows electrochemical CO2 reduction reaction (CO2RR) with the potential to tackle over issues induced by the increased CO2 level in the atmosphere. The associated technological viability of this process is highly dependent on exploring efficient electrocatalysts. In this work, we successfully synthesized nitrogen and sulfur co‐doped carbon nanosheets (NS‐CNSs), which are comprehensively characterized by a variety of characterization techniques. When used as the catalyst for CO2RR, the NS‐CNSs exhibit remarkably high catalytic activity and selectivity with a Faradaic efficiency of ∼85.4 % for CO production and long‐term durability. The superior performance of this material majorly originates from the unique nanosheets structure with large porosity and the co‐doped S and N in the nanosheets, which exposed larger electrochemical activity surface areas and more active sites for promoting CO2 reduction. [ABSTRACT FROM AUTHOR]

We report on diode-pumped continuous-wave Tm3+:CaLaGa 3 O 7 lasers, for the first time to our knowledge. Maximum output powers of 176 mW, 148 mW and 102 mW are achieved at 1885 nm, 1913 nm and 1938 nm with slope efficiencies of about 2.3%, 1.8% and 1.1%, respectively. A wavelength tuning is also demonstrated with a range of about 101 nm via an intracavity undoped YAG etalon. [ABSTRACT FROM AUTHOR]

A Pr3+-doped NaGd(WO4)2 single crystal has been grown by the Czochralski technique along the (0 0 1) orientation. The refractive indices were measured precisely as a function of wavelength. A Raman spectrum, polarized absorption spectra, fluorescence spectra, and fluorescence decay curve have been recorded at room temperature. The standard and modified Judd-Ofelt theories have been performed to analyze the absorption spectra to determine the spectroscopic parameters, including the Judd-Ofelt intensity parameters Ωt (t=2,4,6), radiative transition probabilities, radiative lifetimes, and branching ratios. The stimulated emission cross sections and fluorescence lifetime of the promising laser level were obtained. [ABSTRACT FROM AUTHOR]

The crystal of ZnWO4 doped with Co2+ has been grown by the Czochralski technique. The orientation procedure was presented. Along the crystallographic axes, the principal coefficients of thermal expansion and absorption spectra were measured and discussed. Based on the data, the crystal field parameter 10Dq, Racah parameter B, as well as the absorption cross sections were calculated. The nonlinear dependence of optical absorption on concentration of cobalt ions was found and discussed in single crystal Co2+:ZnWO4. The results indicate that inner defects such as natural cleavage or slip faces in crystal are important in the study of optical and thermal properties. [ABSTRACT FROM AUTHOR]

Abstract Intense 2.9 µm emission corresponding to Dy3+:6H 13/2 → 6H 15/2 transition was achieved in Yb3+/Dy3+ codoped CaYAlO 4 crystal for the first time. The effects of Yb3+ on the spectroscopic properties and energy transfer mechanisms were investigated. In comparison with Dy3+ singly-doped CaYAlO 4 crystal, Yb3+/Dy3+ codoped crystal not only has intense 2.9 µm emission, but also has longer upper laser level lifetime, which facilitates particle number inversion and laser behavior in 2.9 µm. Furthermore, the energy transfer efficiency from Yb3+ to Dy3+ in Yb3+/Dy3+ codoped crystal was as high as 87.3%, indicating effective energy transfer of Yb3+. Besides, the energy transfer microscopic parameters between Yb3+ and Dy3+ were theoretically analyzed. The results indicate that the introduction of Yb3+ is very beneficial for achieving 2.9 µm laser in Dy3+: CaYAlO 4 crystal, which could act as a potential gain media for LD pumped mid-infrared laser. [ABSTRACT FROM AUTHOR]

Abstract The spectroscopic characteristics of a series of Dy3+/Tm3+-codoped LaF 3 single crystals have been studied for mid-IR emissions through Dy3+:6H 13/2 → 6H 15/2 transition. Optimal mid-IR emission was achieved in 3 at% Tm3+ and 2 at% Dy3+ co-doped LaF 3 sample under the excitation of 790 nm. Its emission cross section was calculated to be 2.56 × 10–21 cm2 at the peak wavelength (2840 nm) with a FWHM of 270 nm, and the fluorescence lifetime was 3.694 ms. The fact of intense 2.84 µm emission was achieved by 790 nm pumping proves the effective energy transfer from Tm3+ to Dy3+ ions. The possible energy transfer routes were analyzed in detail, and the microscopic transfer constants were also estimated based on the phonon-assisted energy transfer theory. As a result, Dy3+/Tm3+-codoped LaF 3 single crystal can be a potential medium for mid-IR lasers. [ABSTRACT FROM AUTHOR]