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1.
The ESR spectrum of La 3Ga 5SiO 14 single crystals activated by chromium ions is investigated. It is shown that chromium ions are incorporated into the La 3Ga 5SiO 14 crystal lattice in the trivalent state at laoctahedric positions. Orientations of the principal magnetic axes are determined,
and parameters of the spin Hamiltonian are estimated. The effect of disorder of the crystal structure of the matrix on line
widths and shapes of the ESR spectrum of impurity Cr 3+ ions is discussed.
I. Franko L’vov State University, 50, Dragomilov St., L’vov, 290005, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 65, No. 6, pp. 942–946, November–December, 1998. 相似文献
2.
The Er-single-doped and Er/Ce-codoped La 3Ga 5SiO 14 polycrystalline powders are synthesized by the solid-phase synthesis method. The room-temperature luminescence spectra of the samples are investigated. The Near-infrared-region spectroscopic properties of Er 3+ ions in the La 3Ga 5SiO 14 systems are analysed with Judd-Ofelt theory and rate equations. The effective deactivating effect of Ce 3+ ions on Er 3+ ions is confirmed. 相似文献
3.
The morphology and phase composition of the surface of La3Ga5SiO14 (langasite) crystals at annealing in a temperature range 1000–1200°C have been studied using electron and atomic force microscopy. It has been shown that trigonal lanthanum oxide (La2O3) crystals with sizes to 3–4 μm, as well as a microstructure with sizes to 50 μm with gallium excess, with the approximate composition of 15 mol % La2O3, 65 mol % Ga2O3, and 20 mol % SiO2 are formed on the surface of langasite crystals annealed in air at temperatures above 1100°C. Possible reasons for thermal destruction of the compound can be a significant rearrangement of the disordered crystal structure of langasite caused by the interaction with air oxygen and under the intense surface diffusion of atoms of the crystal, as well as the incongruent character of melting of the La3Ga5SiO14 compound. The revealed thermal destruction of the surface of langasite crystals should be taken into account when using this material to fabricate piezoelectric elements for operation at high temperatures. 相似文献
4.
A new method has been proposed to measure the electro-optical coefficients of the crystals which have optical activity. By using this method, the half-wave voltage and the electro-optical coefficients of the optically active crystals La 3Ga 5SiO 14 (LGS), La 3Ga 5..5Nb 0.5O 14 (LGN), La 3Ga 5.5Ta 0.5Si 14 (LGT) have been determined. The resultants obtained are: γ 11(LGS)=1.9 pm/V, γ 11(LGN)=0.75 pm/V, γ 11(LGT)=0.57 pm/V. This method can also be used to simulate the on–off state of the electro-optical Q switch in the laser cavity, whether the switch is made of the ordinary crystals or the optically active crystals. 相似文献
5.
Experimental evidence that nuclear magnetic resonance (NMR) can detect structural changes of piezoelectric La 3Ga 5SiO 14 induced by dilute paramagnetic ions is presented. Gd 3+ and Eu 3+ cations have been incorporated into La 3Ga 5SiO 14 monocrystals. As expected, the line-width of the tetrahedral 29Si magic angle spinning (MAS) NMR spectra as well as the inverse of the T2 relaxation time of 71Ga increases with the concentration of the paramagnetic ions. A surprising result is shown by 71Ga multiple quantum (MQ) MAS NMR spectrum, which changes with the concentration of paramagnetic ions. The changes in the 71Ga MQMAS spectra can be explained by a more ordonated distribution of Ga ions inside the oxygen tetrahedra. The 71Ga MQMAS NMR spectra allow identification of the one octahedral and two tetrahedral Ga sites. 相似文献
6.
Preparation of Er 3+, Ho 3+ and Tm 3+ ions co-doped SiO 2 nanoparticle phosphor powders by sol gel method is reported. The morphology and the particle size of the SiO 2 host matrix were confirmed by field emission scanning electron microscopy (FESEM). Ultraviolet, visible (UV/VIS) and cathodoluminescence measurements were carried out in order to investigate the optical properties of our powder phosphors. Green emissions at 520 nm from Er 3+ and 544 nm from Ho 3+, and red emissions at 665 nm from both Er 3+ and Ho 3+ ions are reported. Another emission peak in the near infra-red (NIR) region at 875 nm from Er 3+ was also measured. Blue emission at 460 nm, red at 705 nm and a NIR peak in the region of 865 nm from Tm 3+ were observed. Red, green and blue (RGB) colours were measured from both SiO 2:Er 3+,Tm 3+ and SiO 2:Ho 3+,Tm 3+ systems. The change in the intensities of the emission peaks in both the SiO 2:Ho 3+,Tm 3+ and SiO 2:Er 3+,Tm 3+ systems with the change in accelerating beam voltage is shown. Energy transfer from Tm 3+ ions to Er 3+ and Ho 3+ ions was observed. A mechanism explaining the increase and decrease behaviour of the emission with accelerating beam voltage from both systems is reported. 相似文献
7.
利用X射线粉末衍射确定了Tm 3+掺杂硅酸镓镧(La 3Ga 5SiO 14,LGS)晶体的晶体结构;运用DICVOL91程序计算了该晶体不同部位的晶胞参数;测定了Tm:LGS晶体的室温吸收谱和470nm光激发下的发射光谱;根据Judd-Ofelt理论拟合了Tm 3+的三个晶场调节参数 Ωt( t=2,4,6),分别为2.694×10 -20cm 2,1.842×10 -20cm 2,0.030×10 -20cm 2;计算了各个能级跃迁的谱线强度、振子强度、吸收截面等,进而计算了 3H 4和 3F 4态的自发跃迁概率、辐射寿命、荧光分支比和积分发射截面,并对结果进行了分析.
关键词:
Tm:LGS晶体
吸收谱
Judd-Ofelt理论
光谱参数 相似文献
8.
The frequency-field and orientation dependences of the electron paramagnetic resonance (EPR) spectra are measured for impurity Tm 3+ ions in yttrium orthosilicate (Y 2SiO 5) single crystals by stationary EPR spectroscopy in the frequency range of 50–100 GHz at 4.2 K. The position of the impurity ion in the crystal lattice and its magnetic characteristics are determined. The temperature dependences of the spin–lattice and phase relaxation times are measured by pulse EPR methods in the temperature range of 5–15 K and the high efficiency of the direct single-phonon mechanism of spin–lattice relaxation is established. This greatly shortens the spin–lattice relaxation time at low temperatures and makes impurity Tm 3+ ions in Y 2SiO 5 a promising basis for the implementation of high-speed quantum memory based on rare-earth ions in dielectric crystals. 相似文献
9.
The polarization rotating coefficient and the laser-damage threshold of La 3Ga 5SiO 14 crystal at 1064 nm are measured, which are 1.1 deg/mm and , respectively. The working principle and the design method of electrooptic Q-switch based on La 3Ga 5SiO 14 crystal, which has the optical activity, are reported. The performance of Nd:YLF laser with the electrooptic Q-switch of La 3Ga 5SiO 14 crystal was studied. The output pulses with an energy of 379 mJ, a duration of 8.7 ns and repetition of 10 Hz are achieved. 相似文献
10.
The variation of the resonance frequency of piezoelectric resonators subjected to a constant electric field is demonstrated
with longitudinal vibrations in La 3Ga 5SiO 14 (langasite) crystal rods at temperatures between −60 and +80°C. For the rods whose longtudinal axis makes angle α with the
crystal axis
in the plane of the axes
and [0001], the change in the frequency is proportional to the field strength and depends on α. For a field of ±1.5 × 10 6 V/m and α = 15°, the relative change in the frequency is ±120 × 10 −6. It is shown that La 3Ga 5SiO 14 crystals offer a set of physical parameters that makes them promising for electrically controlled acoustoelectronic devices
and for devices based on nonlinear interaction between acoustic waves. 相似文献
11.
Single crystals of erbium-doped La 3Ga 5.5 Ta 0.5O 14, grown by the Czochralski method, have been investigated using methods of optical spectroscopy. Room-temperature absorption spectra were analysed in the framework of the Judd-Ofelt theory. Radiative transition rates, radiative lifetimes and luminescence branching ratios for luminescent levels of Er 3+ have been evaluated and compared to measured luminescence intensities and lifetimes. The laser potential associated with the 4I 13/2- 4I 15/2 transition near 1.55 μm has been assessed. It has been concluded that La 3Ga 5.5 Ta 0.5,O 14:Er crystal is an intermediate gain laser material exhibiting strong inhomogeneous broadening of absorption bands, advantageous for optical pumping with laser diodes. 相似文献
12.
制备了Tm 3+(8.0mol%)掺杂(77- x)GeO 2- xGa 2O 3-8Li 2O-10BaO-5La 2O 3( x=4,8,12,16)系列玻璃.系统地研究了Ga 2O 3从4mol%变化到16mol%时,玻璃的光谱性质与热学性质的变化规律.差热分析表明,随着Ga 2O 3含量的增加,锗酸盐玻璃的热稳定性增加.运用Judd-Ofelt(J_O)理论计算得到了Tm 3+在不同Ga 2O 3含量的GeO 2-Ga 2O 3-Li 2O-BaO-La 2O 3玻璃中的J-O强度参数( Ω2, Ω4, Ω6)及Tm 3+各激发能级的自发跃迁概率、荧光分支比以及辐射寿命等光谱参量.在808nm激光二极管的激发下,测试并分析了Ga 2O 3对Tm 3+荧光光谱特性的影响.随着Ga 2O 3从4mol%增加到16mol%,Tm 3+在1.8μm处的荧光强度呈现先减弱后增强的特性.当Ga 2O 3含量大约在12mol%时,Tm 3+在1.8μm处的荧光强度最弱,受激发射截面达到最小.还初步讨论了Ga 2O 3对玻璃结构与光谱参数的影响规律.
关键词:
3+掺杂锗酸盐玻璃')" href="#">Tm 3+掺杂锗酸盐玻璃
光谱性能
Judd-Ofelt参数
热稳定性 相似文献
13.
In this paper some spectroscopic properties of Y 3Sc 2Ga 3O 12 (YSGG):Cr,Ho, YSGG:Cr,Tm and YSGG:Cr,Tm,Ho are presented. The three lowest energetic manifolds of Ho 3+ and Tm 3+ in YSGG have been determined at 10 K. Time-resolved fluorescence build-up and decay of the laser active ions was measured in three crystals with different dopant concentrations. The transitions investigated were 5I 7 → 5I 8 for Ho 3+ near 2000 nm and 3H 4 → 3H 6 for Tm 3+ near 1800 nm. The data found on time-resolved fluorescence and energy level positions are useful for the discussion of the energy transfer characteristics of the system. 相似文献
14.
Low temperature quenching and high efficiency CaSc 2O 4:Ce 3+ (CSO:Ce 3+) phosphors co-doped with Tm 3+, La 3+ and Tb 3+ ions were prepared by a solid state method and the phase-forming, morphology, luminescence and application properties of these phosphors were investigated. The results showed that co-doping of Tm 3+, La 3+ and Tb 3+ ions can improve the luminescence properties and decrease temperature quenching of CSO:Ce 3+ phosphor remarkably. High efficiency green-light-emitting diodes were fabricated with the prepared phosphors and InGaN blue-emitting (∼460 nm) chips. The good performances of the green-light-emitting LEDs made from co-doped CSO:Ce 3+ phosphors confirm the luminescence enhancement and indicate that Tm 3+, La 3+ and Tb 3+ co-doped CSO:Ce 3+ phosphors are suitable candidates for the fabrication of high efficiency white LEDs. 相似文献
15.
Thermal stability of the phase composition of langasite family crystals is studied by means of high-temperature X-ray diffractometry upon heating in vacuo and in air. Upon heating above 1000°C in vacuo, the partial decomposition of the initial phase is observed in La 3Ga 5SiO14, La 3Ta 0.5Ga 5.5O 14, and Ca 3TaGa 3Si 2O 14 crystals; this is accompanied by the emergence of gallium-depleted oxides of the main elements, due to the formation of volatile gallium protoxide and the loss of gallium in the surface layer of the crystals. Langasite family crystals are found to be stable when annealed in air up to a temperature of 1200°C. 相似文献
16.
采用化学共沉淀法制备了系列Y 1.98-2xYb 2x Er 0.02SiO 5(0.00≤ x≤0.15)以及Y 1.736Yb 0.24Er 0.02Tm 0.004SiO 5上转换发光材料,比较了室温下Y 1.98-2xYb 2x Er 0.02 SiO 5 ( x=0.00,0.08)样品在400—1600 nm范围内的吸收光谱,测量了所有样品在976 nm OPO激光器激发下的上转换发射光谱,以及Er 3+离子 4S3/2(4F9/2)→4I15/2,Tm 3+离子 1G4→3H6荧光衰减曲线和不同激发功率下的上转换蓝光发射强度,从而分析讨论了Er 3+,Tm 3+在Y 2SiO 5中的上转换发光机理.研究结果表明:在1250 ℃相对较低的温度下合成了X2型单斜晶系Y 2SiO 5 ∶Ln 3+(Ln 3+=Er 3+,Yb 3+,Tm 3+),Yb 3+的敏化显著增强了样品在976 nm附近的吸收能力,并大幅度加宽了该处的吸收带.分析上转换发射光谱发现:上转换绿光和红光强度都随着Yb 3+浓度的增加先增强后减弱,但红光的猝灭浓度较高,归因于Er 3+→Yb 3+反向能量传递ETU4和Yb 3+→Er 3+正向能量传递ETU3过程的发生;上转换蓝光发射是三光子吸收过程,是通过Yb 3+,Tm 3+之间三次声子辅助的能量转移方式实现的.
关键词:
上转换
共沉淀
2SiO 5∶Er 3+')" href="#">Y 2SiO 5∶Er 3+
3+')" href="#">Yb 3+
3+')" href="#">Tm 3+ 相似文献
17.
The broadband near-IR emission has been investigated in a series of Er/Tm co-doped Bi 2O 3–SiO 2–Ga 2O 3 (BSG) glasses with 800 nm laser diode as an excitation source. A broadband emission extending from 1350 to 1650 nm with a full width at half maximum (FWHM) around 165 nm is obtained in 0.2 wt% Er 2O 3 and 1.0 wt% Tm 2O 3 co-doped BSG glass. The fluorescence decay curves of glasses are measured and maximum energy transfer efficiency from Er 3+ to Tm 3+ reaches 71% when Tm 3+ concentration is 1.0 wt%. The temperature dependence of the broadband emission spectra in Er 3+–Tm 3+ co-doped BSG glass is also recorded to further understand the energy-transfer processes between Er 3+ and Tm 3+. The present work suggests that Er/Tm co-doped BSG glasses can be a potential candidate for broadband integrated amplifier. 相似文献
18.
Polarized optical absorption spectra in the range of 450–2000 nm have been recorded for the Czochralski-grown concentration
series of single crystals of mixed scheelite-like molybdates NaLa
x
Gd 1 − x
(MoO 4) 2( x = 0–1) activated by Tm 3+ ions. The intensity parameters Ω
t
( t = 2, 4, 6) of the crystals grown were determined by the Judd-Ofelt method, and the values found were used to estimate the
probabilities and emission branching ratios for a number of radiative transitions of Tm 3+ ions. The main optical constants of an Na 0.909La 0.490Gd 0.498Tm 0.035Mo 2.020O 8.048 crystal were found and the temperature dependences of the refractive index for the ordinary and extraordinary waves were
investigated in the temperature range of 293–373 K. The spectral dependences of the emission cross section for the expected
3
F
4 → 3
H
6 laser transition of Tm 3+ ions in an Na 0.908La 0.301Gd 0.676Tm 0.048Mo 2.019O 8.043 crystal were measured in the spectral range of 1500–2000 nm. The gain cross section of the active medium on the 3
F
4 → 3
H
6 laser transition of Tm 3+ ions in this crystal was calculated using the spectral dependences of the absorption and emission cross sections. 相似文献
19.
A phenomenon of highly efficient cooperative energy transfer from Ho 3+ and Tm 3+ ions to two-particle (2Ce 3+) cooperative acceptors in crystals of solid solutions of La 1?x Ce x F 3 is revealed. The rates of cooperative energy transfer in Ho 3+→2Ce 3+, Tm 3+→2Ce 3+, and Tb 3+→ 2Yb 3+ systems are measured, as well as their dependence on the magnitude of the matrix elements of donor transition. 相似文献
20.
A type of electro-optic Q-switch is designed by using optically active crystal La 3Ga 5SiO 14 (abbreviated as LGS), in which the polarization plane gyration and electro-optic effect exist simultaneously. The configuration of the Q-switch is based on the consideration that the total rotation angle of the polarization plane of the polarized laser is zero, while the laser in the cavity propagates through the Pockels cell back and forth. The Q-switch placed in a Nd 3 +:YAG laser behaves normally, like those without optical activity. Compared with the DKDP Q-switch, the LGS Q-switch has more superiorities, which make it a suitable replacement for the DKDP Q-switch in lasers with medium-output energy. 相似文献
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