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1.
We investigate the influence of gamma-ray irradiation on the absorption and fluorescent spectra of Nd^3+:Y3A15 O12 (Nd: YAG) and Yb^3+ : Y3A15 O12 (Yb: YAG) crystals grown by the Czochralski method. Two additional absorption (AA) bands induced by gamma-ray irradiation appear at 255nm and 340nm. The former is contributed due to Fe^3+ impurity, the latter is due to Fe^2+ ions and F-type colour centres. The intensity of the excitation and emission spectra as well as the fluorescent lifetime of Nd:YAG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, the same dose irradiation does not impair the fluorescent properties of Yb:YAG crystal. These results indicate that Yb: YA G crystal possesses the advantage over Nd: YA G crystal that has better reliability for applications in harsh radiant environment.  相似文献   

2.
The effects of F^- ions in a germanium-lead-tellurite glass system on the spectral and potential laser properties of the Yb^3 are investigated. The absorption spectra, lifetimes, the emission cross-sections and the minimum pump intensities of the glass system with and without F^- ions have been measured and calculated. The results show that the fluorescence lifetime and the minimum pump intensity of Yb^3 ions increase evidently, which indicatesthat germanium-lead-oxyfluoride tellurite glass is a promising laser host matrix for high power generation. FT-IRspectra were used to analyse the effect of F^- ions on OH^- groups in this glass system. Analysis demonstrates that addition of fluoride removes the OH^- groups and results in improvement of fluorescence lifetime of Yb^3 .  相似文献   

3.
The effects of a Mg^2+ ion on the dopant occupancy and upconversion luminescence of a Ho^3+ ion in LiNbO3 crystal are reported. The birefringence gradient of the crystal is measured to investigate the optical homogeneity. The X-ray powder diffraction spectrum and the upconversion luminescence are used to investigate defect structure and spectroscopic properties of Mg,Ho:LiNbO3. Under 808-nm excitation, blue, red, and very intense yellow-green bands are observed. Based on the energy levels of Ho^3+ in LiNbO3, and the pump intensity dependence of the observed emission, an excitation scheme is presented. The upconversion emission spectra reveal an enhancement of upconversion intensity when the Mg^2+ ions are introduced into Ho:LiNbO3. The main upconversion mechanism is discussed in this work.  相似文献   

4.
Ho3+/Yb3+co-doped Li YF4 single crystals with various Yb3+concentrations and ~ 0.98 mol% Ho3+concentration are grown by the Bridgman method under the conditions of taking Li F and YF3 as raw materials and a temperature gradient(40°C/cm–50°C/cm) for the solid–liquid interface.The luminescent performances of the crystals are investigated through emission spectra,infrared transmittance spectrum,emission cross section,and decay curves under excitation by 980 nm.Compared with the Ho3+single-doped Li YF4 crystal,the Ho3+/Yb3+co-doped Li YF4 single crystal has an obviously enhanced emission band from 1850 nm to 2150 nm observed when excited by a 980-nm diode laser.The energy transfer from Yb3+to Ho3+and the optimum fluorescence emission around 2.0 μm of Ho3+ions are investigated.The maximum emission cross section of the above sample at 2.0 μm is calculated to be 1.08×10-20cm2 for the Li YF4 single crystal of1-mol% Ho3+and 6-mol% Yb3+according to the measured absorption spectrum.The high energy transfer efficiency of88.9% from Yb3+to Ho3+ion in the sample co-doped by Ho3+(1 mol%) and Yb3+(8 mol%) demonstrates that the Yb3+ions can efficiently sensitize the Ho3+ions.  相似文献   

5.
裴钰  陈晓峰  秦来顺  姚冬敏  任国浩 《中国物理》2006,15(11):2756-2760
The optical properties of LaCl3:Ce crystal are reported in this paper. Optical transmission spectrum, photoluminescence and time resolved photoluminescence spectra at different temperatures are investigated. It is found that optical transmittance is as high as 80% between 320 nm and 600 nm, and no obvious absorption band is found in this region. Emission intensity and decay time of photoluminescence are quite stable with the change of the temperature between 80 K and 500 K. No thermal quenching is present up to 500 K, and decay time keeps at 17±2 ns. With the increase of the temperature, the whole emission bands and excitation bands present broadening and overlapping, leading to the strengthening of re-absorption of the Ce^3+ emission, which makes the emission spectra have a red shift trend.  相似文献   

6.
Ho^3+ : GdVO4 is a new laser material suitable for high-power laser systems. In this paper we measure the absorption spectra of Ho^3+ in the sample Ho^3+: GdVO4. The intensity parameters are calculated by using the Judd-Ofelt theory. Some predicted spectroscopic parameters, such as the spontaneous radiative transition rate, branching ratio and integrated emission cross section are dealt with. And we also compare the optical parameters with those of other materials. From these results, it is found that there are many transitions which have large oscillator strengths and large integrated emission cross sections. Especially the transitions such as ^5 F4 → ^5 I 8, ^5 S2→^5 I8, ^5 F5 → ^5 I8 and ^5 I7 →^ 5 I8 are useful in solid-state lasers and other fields. Finally, we discuss the splitting of the energy levels of Ho^3+ in the crystal GdVO4 based on the group theory.  相似文献   

7.
We investigate the absorption, stimulated emission cross section and potential laser parameters of Yb^3 doped gernano-silicate glasses (GSY glass). The emission cross section is evaluated by using the measured absorption spectra and the principle of reciprocity. It is found that Yb^3 in GSY glasses has high stimulated emission cross section of 0.5-0.65pm^2 near 1020nm and exists long measured fluorescence lifetime of 1.20-2.00ms. Compared with other glass hosts, the GSY glass exhibits excellent general spectroscopic properties for Yb^3 -doped double-cladding fibres.  相似文献   

8.
The beam divergence effects of the input pump laser on a high power nanosecond optical parametric oscillator (OPO) have been numerically simulated. The OPO conversion efficiency is affected due to the angular deviation of real laser beams from ideal phase matching conditions. Our theoretical model is based on the decomposition of the Gaussian beam and assumes each component has a single deviation angle and thus a particular wave vector mismatch. We take into account the variable intensity profile in the spatial and temporal domains of the Gaussian beam, the pump depletion effects for large-signal processes as well as the oscillatory effects of the three waves. Two nonlinear crystals β-BaB2O4 (BBO) and LiB305 (LBO) have been investigated in detail. The results indicate that the degree of beam divergence strongly influences the maximum pump intensity, optimum crystal length and OPO conversion efficiency. The impact of beam divergence is much more severe in the case of critical phase-matching for BBO than in the case of non-critical phase-matching for LBO. The results provide a way to choose the optimum parameters for a high power ns OPO such as the nonlinear material, the crystal length and the pump intensity, etc. Good agreement is obtained with our experimental results.  相似文献   

9.
Yb3+:Er3+:Tm3+ co-doped borosilicate glasses are prepared.Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared,which are excited by a 978-nm laser diode,are measured,and the mechanisms of energy transfer among Yb3+,Er3+ and Tm3+ ions are discussed.The results show that there is an unexpected wavelength at 900-nm emission from Yb3+ Stark splitting levels to pump Tm3+ ions and there exists an optimum pump power.The concentration of the Tm3+ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the Yb3+:Er3+:Tm3+ co-doped borosilicate glasses.  相似文献   

10.
The absorption and emission spectra of the YVO4 single crystal co-doped with 1 at.% Nd^3+ and 1 at.% Yb^3+ are investigated. The efficient Nd^3+ → Yb^3+ energy transfer and the back transfer (Yb^3+ → Nd^3+) are observed at room temperature. The fluorescence lifetime of the 4F3/2 level of Nd^3+ in Nd,Yb:YVO4 is measured under 808 nm laser light excitation. The efficiency of Nd^3+ → Yb^3+ energy transfer in YVO4 is determined to be about 34%.  相似文献   

11.
Ca3Y2 (BO3)4:Eu^3+ phosphor is synthesized by high temperature solid-state reaction method, and the Iuminescence characteristics are investigated. The emission spectrum exhibits two strong red emissions at 613 and 621 nm corresponding to the electric dipole ^5 Do- ^7F2 transition of Eu^3+ under 365 nm excitation, the reason is that Eu^3+ substituting for Y^3+ occupies the non-centrosymmetric position in the crystal structure of Ca3 Y2 (BO3)4. The excitation spectrum for 613 nm indicates that the phosphor can be effectively excited by ultraviolet (UV) (254 nm, 365nm and 400nm) and blue (470nm) light. The effect of Eu^3+ concentration on the emission intensity of Ca3 Y2 (BO3)4 :Eu^3+ phosphor is measured, the result shows that the emission intensities increase with increasing Eu^3+ concentration, then decrease. The CIE colour coordinates of Ca3Y2 (BO3)4:Eu^3+ phosphor is (0.639, 0.357) at 15mol% Eu^3+.  相似文献   

12.
We report a thin film electroluminescent device with a three-layer structure (diamond/CeF3/SiO2 films), which has a luminance of 1.5 cd/m^2 at dc voltage 215 V. The electroluminescence spectrum at room temperature shows that the main peaks locate at 527 and 593nm, which are attributed to isolated emission centers of Ce^3+ ions.  相似文献   

13.
The novel vacuum ultraviolet (VUV) excited Na3 Y9O3 (BO3)8:Tb^3+ (NYOB:Tb^3+) green phosphor is prepared. Strong VUV photoluminescence and high quenching concentration of Tb^3+ (20 wt%) are observed in NYOB: Tb^3+ and the strong emission are correlated with the unique layer-type structure of NYOB. All the characteristic 4 f - 5d transitions of Tb^3+ and the host absorption band in VUV region are identified in the excitation spectrum. Based on the results, the energy levels scheme of Tb^3+ in NYOB:Tb^3+ is first established. This newly developed NYOB:Tb^3+ phosphor shows excellent optical properties when compared with the commercial Zn2SiO4:Mn^2+ and would be a potential VUV-excited green phosphor.  相似文献   

14.
A n atomic-layer-deposited Al2O3/HfO2/Al2O3 (A/H/A) tunnel barrier is in vestigated for Co nanocrystal memory capacitors. Compared to a single Al2O3 tunnel barrier, the A/H/A barrier can significantly increase the hysteresis window, i.e., an increase by 9 V for ±12 V sweep range. This is attributed to a marked decrease in the energy barriers of charge injections for the A/H/A tunnel barrier. Further, the Co-nanocrystal memory capacitor with the A/H/A tunnel barrier exhibits a memory window as large as 4.1 V for 100 μs program/erase at a low voltage of ±7 V, which is due to fast charge injection rates, i.e., about 2.4× 10^16 cm^-2 s^-1 for electrons and 1.9× 1016 cm^-2 s^-1 for holes.  相似文献   

15.
The compressional behavlour of natural pyrope garnet is investigated by using angle-dlspersive synchrotron radiation x-ray diffraction and Raman spectroscopy in a diamond anvil cell at room temperature. The pressureinduced phase transition does not occur under given pressure. The equation of state of pyrope garnet is determined under pressure up to 25.3 GPa. The bulk modulus KTO is 199 GPa, with its first pressure derivative K′TO fixed to 4. The Raman spectra of pyrope garnet are studied. A new Raman peak nearly at 743 cm^-1 is observed in a bending vibration of the SiO4 tetrahedra frequency range at pressure of about 28 GPa. We suggest that the new Raman peak results from the lattice distortion of the SiO4 tetrahedra. All the Raman frequencies continuously increase with the increasing pressure. The average pressure derivative of the high frequency modes (650-1000 cm^-1) is larger than that of the low frequency (smaller than 650 cm^-1). Based on these data, the mode Grǖneisen parameters for pyrope are obtained.  相似文献   

16.
Charge trapping characteristics of the metal-insulator-silicon (MIS) capacitors with Si02/HfO2//A12O3 stacked dielectrics are investigated for memory applications'. A capacitance-voltage hysteresis memory window as large as 7.3 V is achieved for the gate voltage sweeping of ±12 V, and a fiat-band voltage shift of 1.5 V is observed in terms of programming under 5 V and I ms. Furthermore, the time- and voltage-dependent charge trapping characteristics are also demonstrated, the former is related to charge trapping saturation and the latter is ascribed to variable tunnelling barriers for electron injecting and discharging under different voltages.  相似文献   

17.
Lead-free piezoelectric ceramics 0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3 + xmol% Co3+ (BNBT-Co, x = 0-8) are prepared by the solid state reaction method. Effects of the amount of Co^3+ on the electrical properties and phase transition are studied. The results indicate that the addition of Co^3+ enhances the mechanical quality factor Q^3+ significantly, whereas the dissipation factor tanδ has a minimum value at x = 3.5. Meanwhile, addition of Co^3+ leads to small decreases of piezoelectric constant d33, and planar electromechanical coupling kp. The present 0.92(Bio.aNao.5) TiO3-0.08BaTiO3+3.5 moi% Co^3+ ceramics exhibit good performance with mechanical quality factor Qm = 910, piezoelectric constant d33 = 106pC/N, planar electromechanical coupling kp =10% and dissipation factor tanδ = 1.1% at 1 kHz. Saturated polarization hysteresis loops have been obtained for BNBT-Co ceramics. Two dielectric peaks at depolarization temperature Td and Tm appear in the curves of ε33^T vs temperature for the pure BNBT ceramics. However, the first dielectric peak Td disappears after the addition of Co^3+, which means that the transition from ferroelectric to antiferroelectric phase has been eliminated.  相似文献   

18.
Bi3.25La0.75 Ti3O12 (BLT) ferroelectric thin films are deposited by sol-gel method and annealed for crystallizaion in total l eccm N2/02 mixed gas with various ratio at 750℃ for 30rain. The effect of crystallization ambient on the structural and ferroelectric properties of the BLT films is studied. The growth direction and grain size of BLT film are revealed to affect ferroeleetric properties. Alter the BLT film is annealed in 20%O2, the largest P~ value is obtained, which is ascribed to an increase of random orientation and large grain size. The fatigue property is improved with the concentration of oxygen in the ambient increasing, which is ascribed to annealing in the ambient with high concentrated oxygen adequately decreasing the defects related to lack of oxygen.  相似文献   

19.
The high-temperature dielectric properties of SiO2/Si3N4 nanocomposites are investigated theoretically and experimentally. Its permittivities and loss tangents at the temperature ranging from room temperature to 1300°C at 9.0GHz are measured by the resonant cavity method. The SiO2/Si3N4 nanocomposites show complex dielectric behaviour at elevated temperature, and a multi-scale model is proposed to describe the dependence of the dielectric properties in the SiO2/Si3N4 on its compositional variations. Such a theory is needed so that the available property measurements could be extrapolated to other operating frequencies and temperatures.  相似文献   

20.
La0.8Sr0.2AlO3 (LSAO) thin films are grown on SrTiO3 (STO) and MgO substrates by laser molecular beam epitaxy. The LSAO thin film on oxygen deficient STO substrate exhibits metallic behaviour over the temperature range of 80--340K. The optical transmittance spectrum indicates that theLSAO thin films on MgO substrate are insulating at room temperature. The transport properties of LSAO thin films on STO substrates deposited in different oxygen pressure are compared. Our results indicate that oxygen vacancies in STO substrates should be mainly responsible for the transport behaviour of LSAO thin films.  相似文献   

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