Infrared and visible spectroscopic studies of the ytterbium doped borate Li6Y(BO3)3

The spectroscopic study of trivalent ytterbium doped Li₆Y(BO₃)₃ is conducted in the UV-visible and infrared range. An excitation in the charge transfer band of ytterbium has been selected in order to reduce the reabsorption effect on the IR emission intensity. The maximum of the emission is located at 972 nm for an excitation at 230 nm. The energy level assignment has been successfully conducted using vibrational spectroscopy to distinguish the pure electronic transitions from the phonon-assisted ones. The splitting of the ²F_5/2 and ²F_7/2 components is equal to 523 cm⁻¹ and 676 cm⁻¹, respectively. The decay time dependence as a function of the concentration is also reported. The calculated value τ_rad is about (1.03 ± 0.01) ms for the 1% doped material. For the highest concentration, an IR excitation gives rise to the observation of a blue-green luminescence caused by two mechanisms: an erbium emission at 550 nm after upconversion and a cooperative luminescence of ytterbium ions.     

Growth and spectroscopic characterization of Er: Sr3Y(BO3)3 crystal

This paper reports the growth and spectroscopic characterization of Er³⁺:Sr₃Y(BO₃)₃ crystal. Er³⁺:Sr₃Y(BO₃)₃ crystal with dimensions up to ∅20×35 mm³ has been grown by Czochralski method. The polarized spectroscopic properties of Er³⁺:Sr₃Y(BO₃)₃ crystal were investigated. Based on the Judd-Ofelt theory, the effective intensity parameters Ω_t were obtained: Ω₂=1.71×10⁻²⁰ cm², Ω₄=1.39×10⁻²⁰ cm², Ω₆=0.74×10⁻²⁰ cm² for π-polarization, and Ω₂=1.77×10⁻²⁰ cm², Ω₄=1.44×10⁻²⁰ cm², Ω₆=0.65×10⁻²⁰ cm² for σ-polarization. The emission cross-section σ_em was calculated to be 4.75×10⁻²¹ cm² for π-polarization at 1536 nm and 6.30×10⁻²¹ cm² for σ-polarization at 1537 nm. The investigated results showed that Er³⁺:Sr₃Y(BO₃)₃ crystal may be regarded as a potential laser host material for 1.55 μm IR solid-state lasers.     

Yb and Yb-Eu luminescent properties of the Li2Lu5O4(BO3)3 phase

The luminescence of Yb³⁺ in the oxyborate Li₂Lu₅O₄(BO₃)₃ is reported. At low temperature, in addition to the usual ytterbium infrared emission, this phosphor presents an emission in the ultraviolet () which corresponds to the transition from the charge transfer state (O-Yb) to the 4f levels of Yb³⁺. The temperature quenching Tq50% is equal to 120 K. The infrared emission studied at room temperature is located between 950 and 1100 nm.Europium emission quenching in the Li₂Yb₅O₄(BO₃)₃ phase is related to Eu→Yb transfer by cross-relaxation. The reverse Yb→Eu transfer by cooperative sensitization is highlighted in the codoped Li₂Lu₅O₄(BO₃)₃ compound.     

Growth and laser properties of Nd:Ca4YO(BO3)3 crystal

Nd:Ca₄YO(BO₃)₃ (Nd:YCOB) crystal was grown by the Czochralski method, and its structure was measured by using a four circle X-ray diffractometer. The transparent spectrum from 200 to 2600 nm was measured at room temperature. The fluorescence spectrum near 1.06 μm showed that the main emission wavelength of Nd:YCOB crystal was centered at 1060.8 nm. Laser output at 1.06 μm has been demonstrated when it was pumped by a Ti:sapphire laser at the wavelength of 794 nm, the highest output power was 68 mW under pumping power of 311 mW, the pumping threshold was 163 mW and slope efficiency was 46.9%. The self-frequency doubled green light has been observed when it was pumped by a Ti:sapphire or a laser diode (LD). A 14.5 mm Nd:YCOB crystal sample cut at (θ, φ)=(90°, 33°) was used for type I second-frequency generation (SHG) of the 1.06 μm laser pulse. The SHG conversion efficiency was 22%.     

Energy transfer in Li6Gd(BO3)3

The synthesis and structure of the new one-dimensional material Li₆Gd(BO₃)₃ are described. The Gd³⁺ fluorescence is studied from 300 to 1.5 K after selective pulsed excitation into the ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ manifold. Above 40 K the fluorescence decays indicate fast diffusion of the energy among intrinsic and perturbed Gd³⁺ ions, and trapping by impurities. Below 40 K the energy transfer takes place dominantly towards perturbed Gd³⁺ ions and is diffusion limited. This behaviour is discussed in relation with the quasi one-dimensional crystal structure.     

中子探测晶体Li6Gd(BO3)3:Ce的光谱特性研究

文章用提拉法生长出Li₆Gd(BO₃)₃:Ce晶体,并对其光谱性能与发光过程进行了探索. 借助于真空紫外-紫外透过光谱测试,发现晶体的透过光谱中存在Ce³⁺离子和Gd³⁺的特征吸收峰,同时还存在与Ce⁴⁺离子相关的电荷迁移带. 对晶体的真空紫外-紫外激发发射光谱进行研究发现,在晶体存在着Ce³⁺离子的5d→4f辐射跃迁发光与Gd³⁺离子的4f→4f辐射跃迁发光,而且存在着Gd³⁺→Ce³⁺之间的能量传递. 对Li₆Gd(BO₃)₃:Ce晶体的X射线与γ射线激发发射光谱研究可知,晶体在高能射线激发下的闪烁光主要是Ce³⁺离子的发光. 关键词： 6Gd(BO₃)₃:Ce晶体')" href="#">Li₆Gd(BO₃)₃:Ce晶体 真空紫外-紫外透过光谱 真空紫外-紫外激发发射光谱 能量传递     

Radiation-stimulated defects into LaB3O6 and Li6Gd(BO3)3:Ce single crystals

The radiation-induced defect types in LaB₃O₆ and Li₆Gd(BO₃)₃:Ce single crystals have been determined taking into account crystal-lattice features, absorption characteristics, photo- and thermostimulated luminescence data. The possible activator center models in Li₆Gd(BO₃)₃:Ce crystals are proposed.     

Growth and characterization of Nd-doped disordered Ca3Gd2(BO3)4 crystal

A high-quality disordered Nd³⁺:Ca₃Gd₂(BO₃)₄ (Nd³⁺:CGB) laser crystal was grown by the Czochralski method. The space group and effective segregation coefficient of Nd³⁺ were determined to be Pnma and 1.06, respectively. The thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were systematically measured for the first time. It was found that the thermal conductivity increases with increasing temperature, indicating glasslike behavior. The polarized spectral properties of the crystal were investigated, including the polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay. The spectroscopic parameters of Nd³⁺ ions in Nd³⁺:CGB crystal have been obtained based on Judd–Ofelt theory. The anisotropy of the spectral properties for different polarized directions was discussed. Additionally, the continuous-wave (CW) laser performance at 1.06 μm was demonstrated for the first time. The maximum output power of 603 mW was achieved with corresponding optical conversion efficiency of 8.33% and slope efficiency of 9.95%.     

Spectroscopy of Ca3(BO3)2: Dy crystal

Dy³⁺: Ca₃(BO₃)₂ crystal was grown successfully by the Czochraski technique. The absorption spectrum was measured and its absorption peaks were assigned. The Judd-Ofelt intensity parameters were found to be Ω₂=5.216×10⁻²⁰, Ω₄=1.858×10⁻²⁰, Ω₆=0.623×10⁻²⁰ 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. Also, room temperature luminescence decay curve in correspondence with the emission line ⁴F_9/2→⁶H_13/2 centered at 575 nm was measured.     

Investigation of the iron borates DyFe3(BO3)4 and HoFe3(BO3)4 by the method of Er spectroscopic probe

Temperature-dependent high-resolution optical spectra of the Er³⁺ probe ion in DyFe₃(BO₃)₄ and HoFe₃(BO₃)₄ are reported. The data provide the temperature of magnetic ordering and direction of the Fe³⁺ magnetic moments. Both compounds order magnetically at TN=39±1 K$T_{\mathrm{N}}=39\pm 1\text{ K}$. The magnetic structure of DyFe₃(BO₃)₄ is of the easy-axis type, while that of HoFe₃(BO₃)₄ is of the easy-plane type. The role of anisotropic interactions between the iron and the rare-earth subsystems is discussed.     

Spectroscopic properties of Tm -doped Ba3Gd2(BO3)4 crystal

crystal with the size up to Φ 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.     

Polarized spectroscopic properties of Nd-doped KGd(WO4)2 single crystal

The polarized absorption spectra, infrared fluorescence spectra, upconversion visible fluorescence spectra, and fluorescence decay curve of orientated Nd³⁺:KGd(WO₄)₂ crystal were measured at room-temperature. Some important spectroscopic parameters were investigated in detail in the framework of the Judd-Ofelt theory and the Fuchtbauer-Ladenburg formula. The effect of the crystal structure on the spectroscopic properties of the Nd³⁺ ions was analyzed. The relation among the spectroscopic parameters and the laser performances of the Nd³⁺:KGd(WO₄)₂ crystal was discussed.     

Luminescence properties of BaWO4 single crystal

UV excited photoluminescence from BaWO₄ (BWO) single crystals has been investigated in the temperature range of 77-300 K. The presence of two emission bands in the UV and blue spectral regions is observed under excitation by 230 nm at room temperature. The observation of UV emission band at room temperature is a novel result. The thermal treatment at elevated temperatures under air or vacuum is observed to influence the optical and luminescence properties of the crystal. The changes brought about by annealing in air are found to be reversible. However, in vacuum annealed samples the UV emission is completely quenched.     

The Yb to Er energy transfer in YAl3(BO3)4 crystal

The Yb³⁺ to Er³⁺ energy transfer in yttrium aluminum borate (YAB) crystal is investigated with the rate equation without considering the back energy transfer. The energy transfer coefficients (W₂₅) in the crystals with different Yb³⁺ concentrations are determined and compared with those in other crystals. The transfer efficiencies and the micro-parameters of energy transfer and migration are also determined. The results show that the energy transfer from Yb³⁺ to Er³⁺ in YAB crystal is very efficient and the Yb³⁺–Er³⁺ co-doped YAB crystal may be a good candidate for the 1.55 μm laser media.     

Nature of optical properties of GdFe3(BO3)4 and GdFe2.1Ga0.9(BO3)4 crystals and other 3d5 antiferromagnets

Influence of the partial substitution of paramagnetic Fe³⁺ ions by diamagnetic Ga³⁺ ions in the trigonal crystal GdFe₃ (BO₃)₄ on its optical and magnetic properties is studied and discussed in connection with problems common for all antiferromagnets containing 3d ⁵ ions. Polarized optical absorption spectra and linear birefringence of GdFe₃ (BO₃)₄ and GdFe_2.1Ga_0.9 (BO₃)₄ single crystals have been measured in the temperature range 85–293 K. Specific heat temperature dependence (2–300 K) and structure of GdFe_2.1Ga_0.9 (BO₃)₄ crystal have been also studied. As a result of substitution of 30% Fe to Ga the Neel temperature diminishes from 38 till 16 K, the strong absorption band edge shifts on 860 cm^-1 (0.11 eV) to higher energy and the d-d transitions intensity decreases substantially larger than the Fe concentration does. Strong absorption band edge is shown to be due to Mott-Hubbard transitions. Correlation between position of the strong absorption band edge and the Neel temperature of antiferromagnets has been revealed. Properties of the doubly forbidden d-d transitions in the studied crystals and in other antiferromagnets are explained within the framework of the model of the exchange-vibronic pair absorption, which is theoretically analyzed in detail. The model permitted us to determine the connection between parameters of d-d absorption bands (intensity, width and their temperature dependences), on the one hand, and the exchange, spin-orbit and electron-lattice interactions, on the other hand.     

Synthesis and luminescence properties of red-emitting phosphors NaY0.87Eu0.13(WO4)1.2(MoO4)0.8

A series of NaY_1−yEu_y(WO₄)_2−x(MoO₄)_x (x=0−2 and y=0.06−0.15) phosphors have been prepared by a combustion route. X-ray powder diffraction, photoluminescence excitation and emission spectra were used to characterize the resulting samples. The excitation spectra of these phosphors show the strongest absorption at about 396 nm, which matches well with the commercially available n-UV-emitting GaN-based LED chip. Their emission spectra show an intense red emission at 616 nm due to the ⁵D₀→⁷F₂ electric dipole transition of Eu³⁺. As the Mo content increases, the intensity of the ⁵D₀→⁷F₂ emission of Eu³⁺ activated at wavelength of 396 nm increases and reaches a maximum when the relative ratio of Mo/W is 2:3. The intense red-emission of the tungstomolybdate phosphors at near-UV excitation suggests that the material is a potential candidate for white light emitting diode (WLEDs).     

Luminescent properties of a novel red-emitting phosphor: Eu-activated Ca3Sr3(VO4)4

A new luminescent material, Eu³⁺ activated Ca₃Sr₃(VO₄)₄, was investigated. This compound shows a strong red emission centered at 618 nm under near-UV light with two distinct absorption bands; charge transfer state of VO₄³⁻ and f-f transitions of europium ions. As the europium concentration is increased, an additional red-emitting phosphor, EuVO₄, which is known to be a prominent luminescent material in the near-UV region can be traced. The UV excited luminescent properties of this material may find application in the production of red phosphors for white light-emitting diodes.     

Measurement of electro-optic coefficients of low symmetry crystal GdCa4O(BO3)3

In this paper, we report all of the electro-optic coefficients of the low symmetry crystal GdCa₄O(BO₃)₃ measured by the interferometric method. The new sample orientations, which have not been reported so far, have been used for measuring the skew electro-optic coefficients γ₅₁, γ₅₃, γ₄₂ and γ₆₂ independently. The results obtained are γ₁₁=0.4, γ₂₁=0.5, γ₃₁=0.6, γ₁₃=0.1, γ₂₃=0.4, γ₃₃=2.0, γ₅₁=0.7, γ₅₃=1.5, γ₄₂=0.5, γ₆₂=0.8×10⁻¹²m/V.     

Terahertz spectroscopy of multiferroic EuFe3(BO3)4

The terahertz spectra of a rare-earth iron borate with the huntite structure are obtained for the first time. We study the low-temperature (4.0–90 K) α-polarized transmittance spectra of the EuFe₃(BO₃)₄ single crystal in the region 0.9–6.0 THz. Pronounced shifts of phonon frequencies and appearance of new phonon modes at the temperature _TS=58 K$T_S=58\text{K}$ of the R32→P₃₁21$R32\to P{3}_{1}21$ structural phase transition are observed. Additional shifts of phonon frequencies occur at the temperature _TN=34 K$T_N=34\text{K}$ of the magnetic ordering of the Fe subsystem, thus evidencing the spin–phonon coupling in this multiferroic material.     

Li2K(IO3)3与Li2NH4(IO3)3的晶体结构

本文用X射线粉末法测定了Li₂K(IO₃)₃与Li₂NH₄(IO₃)₃的晶体结构和原子参数。发现Li₃K(IO₃)₃,Li₂NH₄(IO₃)₃与Li₂Rb(IO₃)₃同晶型,属单斜晶系,空间群为P2₁/α,每个单胞含有四个化合式量。室温的点阵常数分别为α=11.198?,b=11.046?,c=8.254?,β=111.53°,及α=11.327?,b=11.078?,c=8.341?,β=111.87°。讨论了二元化合物的形成与离子半径的关系。 关键词：