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1.
Investigations of EuGa2S4 have been done on the photoluminescence (PL) related to the transition between 4f65d and 4f7 configuration of the Eu2+ ion and its excitation (PLE) spectra, Raman scattering and infrared absorption. The energies of phonons coupled to the ground and the excited states of the transition are analyzed to be 34 and 19 meV from the shapes of the PL and PLE bands, respectively. The former corresponds to the energy of the Raman line showing the highest intensity. The latter is close to the value obtained from analysis of the temperature dependence of the half width of the PL band. These correspondences indicate that the relevant emission of EuGa2S4 surely has phonon-terminated character. 相似文献
2.
The results of the investigation of dark-current relaxation in EuGa2S4 single crystals are reported. The depth and concentration of the traps are found to be Et = 0.79 eV and Nt = 1.64 × 1014 cm?3, respectively.The charge accumulation region (dc = 3.3 × 10?5 cm) and contact capacitance (Cc = 1.23 × 10?10 F) are also estimated. 相似文献
3.
Z.X. Cheng S.J. ZhangF. Song H.C. GuoJ.R. Han H.C. Chen 《Journal of Physics and Chemistry of Solids》2002,63(11):2011-2017
Erbium and ytterbium codoped double tungstates NaY(WO4)2 crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290-2000 nm have been recorded at room temperature. The Judd-Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er3+ ions in NaY(WO4)2 crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb3+ to Er3+ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels. 相似文献
4.
Ultraviolet fluorescence of Nd3+ ions induced by triphotonic excitation process was studied in Nd-doped LiYF4, LiLuF4 and BaY2F8 crystals using a technique of time-resolved spectroscopy. The observed ultraviolet luminescence was due to transitions between the bottom of 4f25d configuration and 4f3 states of Nd3+ ions. Narrow emission lines superposed to the broadband emissions were observed. A detailed analysis of luminescence spectrum revealed that the narrow emissions are due to parity and spin allowed radiative transitions from the Stark levels of 4K11/2(5d) state created by the electrostatic interaction between the 5d electron and the two electrons of the 4f2 configuration. The narrow emissions are related to the high spin state (S=3/2) which gives f-f characteristics to the f-d broadband emissions. The narrow emissions superposed to the wide emission correspond to 18%, 34% and 43% of the integrated broadband emission at 262 nm observed in LiYF4, LiLuF4 and BaY2F8 crystals, respectively. Although the 5d-4f2 interaction is observed to be weaker than 5d-crystal field interaction, it is stronger enough to select only the radiative transitions from 4f25d configuration to 4f3 states that preserves the total spin S=3/2. 相似文献
5.
Ytterbium-and erbium-doped single crystals of scheelite-like double tungstates NaGd(WO4)2, NaLa(WO4)2, and NaBi(WO4)2 and scheelite CaWO4 have been grown by the Czochralski method. The dopant concentrations in crystals are measured, and the coefficients of dopant
distribution are determined to range from 0.45 to 3. The lifetimes of the Er3+ states 4
I
11/2 and 4
I
13/2 and the Yb3+ state 2F5/2 are measured, and the absorption and luminescence spectra of the crystals are studied in the vicinity of 1.0 and 1.5 μm.
The data obtained are compared with the corresponding characteristics of other crystals. The possible use of the crystals
studied as active media of solid-state lasers operating in the range 1.0 and 1.5 μm is discussed.
__________
Translated from Optika i Spektroskopiya, Vol. 92, No. 4, 2002, pp. 657–664.
Original Russian Text Copyright ? 2002 by Subbotin, Zharikov, Smirnov. 相似文献
6.
Detailed spectroscopic studies of the triply doped KGd(WO4)2:Ho3+/Yb3+/Tm3+ single crystals (which exhibit multicolor up-conversion fluorescence) are reported for the first time. The absorption spectra of crystals were measured at 10 and 300 K; the room temperature luminescence spectra were excited at 980 nm wavelength. The dependence of the intensity of luminescence on the excitation power for three different concentration of Ho3+, Yb3+ and Tm3+ ions was investigated. Efficient green and red up-converted luminescence of Ho3+ ions and weak blue up-conversion luminescence of Tm3+ ions were observed in spectra. The red emission of Ho3+ ions is more intensive than their green emission. Dependence of the up-conversion luminescence intensity on the excitation power and impurities concentration was also studied; the number of phonon needed for efficient up-conversion was determined for each case. All possible energy transfer processes between different pairs of the impurity ions' energy levels are also discussed. 相似文献
7.
Chiharu Hidaka Eri Yamagishi Takeo Takizawa 《Journal of Physics and Chemistry of Solids》2005,66(11):2058-2060
The single crystal of CaGa2S4:Eu is expected as a useful laser material with a high quantum efficiency of light emission. However, as far as our knowledge is concerned, the systematic study of the mixed compounds of Ca(1−x)EuxGa2S4 as a function of x has not been reported up to now. Here, we have first constructed the phase diagram of the CaGa2S4 and EuGa2S4 pseudo binary system, and show that it forms the solid solution. Then we have grown single crystals of these compounds. The maximum photoluminescence efficiency is achieved at x=0.25. From the three peak energies observed in the photoluminescence excitation (PLE) and absorption spectra, the 5d excited states are suggested to consist of three levels arising from the multiplets of Eu2+ ions. 相似文献
8.
T. Watanabe 《Solid State Communications》1973,12(5):355-358
Resistivity and magnetoresistance are measured as functions of temperature (77–450 K) on several FeCr2S4 and CoCr2S4 single crystals (as-grown, annealed in vacuum, annealed in S-atmosphere, and doped) and found to be very sensitive to these treatments. These results are discussed on the basis of the model consisting of donor level due to S-deficiencies in addition to Fe2+ and Cr2+ levels. 相似文献
9.
Luminescence and thermoluminescence properties of nominally pure LiF and CaWO4 crystals are compared with those of the crystalline system LiF/CaWO4. Evidence is found which clearly indicates that from the various emission bands of CaWO4 crystals only the blue one is of intrinsic nature. Luminescence decay measurements are reported. Within the spectral range of the blue tungstate band in LiF/CaWO4 four different decay times are obtained. This result is interpreted as arising from WO2-4 luminescence centres with different environments in the LiF host. 相似文献
10.
Na0.4Y0.6F2.2:Tm3+ crystals with thulium contents of 0.5–20% have been grown by the Stockbarger-Bridgman method. The concentration dependences
of the steady-state spectra and luminescence kinetics from the 3
H
4 and 3
F
4 thulium levels upon selective laser excitation of a series of Na0.4Y0.6F2.2:Tm3+ crystals (0.5–20% Tm) are investigated. It is shown that the luminescence from the 3
H
4 level becomes significantly quenched with an increase in the concentration due to the nonradiative energy transfer. No concentration
quenching of luminescence from the 3
F
4 level is observed. Possible schemes of self-quenching are considered for the 3
H
4 thulium level, the self-quenching microparameters and macrorates are estimated using model quantum-mechanical calculation,
and the most likely self-quenching mechanisms and schemes are found from comparison of the calculated and experimental self-quenching
rates. Good agreement is obtained between the experimental and calculated kinetic curves. It is shown that, under pumping
near ∼0.8 μm, self-quenching of the 3
H
4 thulium level leads to effective occupation of the 3
F
4 level and increases the luminescence intensity in the range of 1.7–1.9 μm. It is concluded that Na0.4Y0.6F2.2:Tm3+ crystals are promising active media for tunable lasers in the range of 1.7–1.9 μm, with small thermal loss under laser-diode
pumping near 0.8 μm.
Original Russian Text ? S.é. Ivanova, A.M. Tkachuk, A.A. Mirzaeva, F. Pellé, 2009, published in Optika i Spektroskopiya, 2009,
Vol. 106, No. 6, pp. 922–930. 相似文献
11.
Mn2+-doped Zn2SiO4 phosphors had been prepared by hydrothermal method in stainless-steel autoclaves. Effects of synthesized methods, reaction temperature, ambience of heat treatment on the structure and the luminescence properties of this silicate were studied with X-ray diffraction apparatus (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and fluorescence spectrum. Results show that Zn2SiO4 nanocrystalline can be obtained by hydrothermal method at relatively low temperatures. The absorption pattern shows an absorption edge at about 380 nm originated from ZnO crystals and two absorption bands at about 215 and 260 nm. Mn2+-doped Zn2SiO4 has a luminescence band with the wavelength at about 522 nm under 255 nm excitation, and the luminescent intensity increases after being heat treated. 相似文献
12.
The optical properties of EuGa2S4 and EuGa2S4:Co single crystals in a range of temperatures from 77 to 300 K are investigated. The single crystals are obtained by the Bridgman method and are characterized by tetragonal syngony. The behavior of the optical transitions in the photon energy range 1.70–2.45 eV and the temperature range 77–300 K is determined. It is established that in the energy range 1.77–1.90 eV absorption is associated with transitions of the Co2+ ion, while in the range 2.20–2.40 eV, with indirect allowed optical transitions. 相似文献
13.
用坩埚下降法(Bridgman)生长出了Bi离子掺杂的CdWO4单晶.测定了晶体不同部位的吸收光谱、发射光谱和X射线电子能谱(XPS).Bi离子的掺入引起CdWO4晶体的吸收边从345 nm红移到399 nm.在311 nm, 373 nm,808 nm和980 nm光的激发下,分别观测到中心波长为470 nm,528 nm,1078 nm和较弱的1504 nm四个不同发射带.Bi:CdWO4单晶的XPS谱分别与Bi2
关键词:
Bi离子
荧光光谱
X射线电子能谱
4单晶')" href="#">CdWO4单晶 相似文献
14.
Vijay Singh R.P.S. Chakradhar Isabelle Ledoux-Rak Laurent Badie Fabienne Pelle Svetlana Ivanova 《Journal of luminescence》2009,129(11):1375-1380
New near-infrared luminescent, monoclinic CaAl2O4:Er3+ phosphor was prepared by using the combustion route at furnace temperatures as low as 500 °C in a few minutes. Combustion synthesized phosphor has been well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX) mapping studies. The luminescence spectra of Er3+-doped calcium aluminate were studied at UV (380 nm), vis (488 nm) and IR (980 nm) excitation. Upon UV and vis excitation, the CaAl2O4:Er3+ phosphor exhibits emission bands at ~523 nm and at ~547 nm, corresponding to transitions from the 2H11/2 and 4S3/2 erbium levels to the 4I15/2 ground state. A strong luminescence at 1.55 μm in the infrared (IR) region due to 4I13/2→4I15/2 transition has been observed in CaAl2O4:Er3+ phosphor upon 980 nm CW pumping. In the spectrum of IR-excited up-conversion luminescence, green (~523 and ~547 nm) and red (662 nm) luminescence bands were present, the latter associated with the 4F9/2→4I15/2 transitions of Er3+ ions. Both excited state absorption and energy transfer may be proposed as processes responsible for the population of the 4S3/2 and 4F9/2 erbium levels upon IR excitation. The mechanisms responsible for the up-conversion luminescence are discussed. 相似文献
15.
Kiwan Jang Ilgon Kim Yanlin Huang Changdae Kim 《Journal of Physics and Chemistry of Solids》2006,67(11):2316-2321
Reduction effects on the optical properties of Sm2+ ions doped in SrB4O7 and SrB6O10 crystals were studied by measurements of luminescence intensity decay as a function of time, X-ray irradiation and laser power effects on the photoluminescence. The fluorescence intensity of Sm2+ doped in SrB4O7 and SrB6O10 crystals decreased upon excitation at 488 nm of Ar+ laser and this so-called photo-bleaching effect was highly dependent on the sample preparation conditions. The fluorescence intensity of Sm2+ doped in SrB4O7 decreased about 13%, while it decreased about 55% in the SrB6O10 crystal irradiated with X-ray for 10 h. Differences of photo-beaching effect and other optical properties of Sm2+ doped in SrB4O7 and SrB6O10 are discussed. 相似文献
16.
Characteristics of two green emission bands, G(I) and G(II), and their origin were investigated within 0.4-300 K under photoexcitation in the 3.4-6.0 eV energy range for undoped and Mo6+-, Mo6+ , Y3+-, Mo6+, Nb5+-, Mo6+, Ce3+-, Cr6+-, La3+-, Ba2+- and Cd2+-doped PbWO4 crystals with different concentrations of impurity and intrinsic defects, grown by different methods and annealed at different conditions. The G(I) emission band, observed at low temperatures, located around 2.3-2.4 eV and excited around 3.9 eV, is usually a superposition of many closely positioned bands. The G(I) emission of undoped crystals is assumed to arise from the WO42− groups located in the crystal regions of lead-deficient structure. In Mo6+-doped crystals, this emission arises mainly from the MoO42− groups themselves. The G(II) emission band located at 2.5 eV is observed only in the crystals, containing the isolated oxygen vacancies — WO3 groups. This emission appears at T>160 K under excitation around 4.07 eV as a result of the photo-thermally stimulated disintegration of localized exciton states and subsequent recombination of the produced electron and hole centres near WO3 groups. The G(II) emission accompanies also thermally stimulated recombination processes in PbWO4 crystals above 150 K. Mainly the G(II) emission is responsible for the slow decay of the green luminescence in PbWO4 crystals. 相似文献
17.
The Dy3+-doped NaY(MoO4)2 single crystals were grown successfully by the Czochralski technique. The main spectroscopic properties (absorption, luminescence, decay curve) of Dy3+-doped NaY(MoO4)2 have been determined for both the σ and π polarizations. By using the Judd-Ofelt theory, the measured room temperature absorption spectra were applied to determine the intensity parameters, spontaneous transition probabilities, branching ratios, and radiative lifetimes of Dy3+ transitions. The results show that the Dy3+-doped NaY(MoO4)2 crystal may realize the yellow laser operation. 相似文献
18.
P. Haro-González L. L. Martín I. R. Martín M. Berkowski W. Ryba-Romanowski 《Applied physics. B, Lasers and optics》2011,103(3):597-602
Comparative investigation of the optical amplification properties of dysprosium doped Gd2SiO5, Lu2SiO5 and YAl3(BO3)4 single crystals was performed in a pump-and-probe experiment. High power laser pulses at 475 nm were used as the pump source
in order to strongly populate the 4F9/2 level of the Dy3+ ions due to ground state absorption. Low signal beam cw radiation at 574 nm was used as the probe beam to stimulate the emission
associated with the 4F9/2→6H13/2 electronic transition of the Dy3+ ions. The process was modelled as a three levels system, and their populations were analysed and simulated in order to study
the gain dynamics. Positive optical gain was observed and compared in these crystals. These results confirmed that among the
systems studied the Dy3+-doped YAl3(BO3)4 single crystal can be considered as a good candidate to develop an optical amplifier employing the 4F9/2→6H13/2 transition at around 574 nm which is the first step to consider as laser active media. 相似文献
19.
Partly deuterated NH4HSeO4 crystals were grown from solutions containing 10, 20, 30, 40, 50 and 60% molar deuterium. The deuteration process leads to an increase in the phase transition temperatures. The extrapolated value of ΔTc(∞) for completely deuterated crystals is 25 K. The I2 ? B2(C32) (if a axis is parallel to [110]) symmetry and the ferroelectric transition related to it is observed only in crystals growing from solution containing less than 50% deuterium. The crystals growing from solution containing more than 50% deuterium have a P212121(D42) symmetry. 相似文献
20.
The luminescence of powder samples of the well-known green-emitting Zn2SiO4:Mn and the red-emitting Mg4Ta2O9:Mn phosphor shows a considerable fine structure at 4° K in appropriately prepared samples containing a sufficiently low Mn concentration. For (Zn1-xMnx)2SiO4 (0.0005?x?0.05) two sharp lines were found which are interpreted as due to zero phonon transitions between the 4T1 and 6A1 levels of Mn2+ ions on the two crystallographically different zinc sites. The remaining structure is ascribed to vibronic sidebands. The decay times of the luminescence bands associated with the two sites differ; they are 12 and 15 ms for the high and low energy bands respectively. The experimental results of Vlam are confirmed by our data. In addition some (Zn1-yBey)2SiO4:Mn (0.025? y ?1) samples were investigated. In Mg4Ta2O9:Mn two zero phonon lines could be identified, indicating that in this material Mn2+ is distributed over two inequivalent Mg sites. Most of the phonon replicas were found at intervals of 15 meV. Raman scattering experiments showed that this energy corresponds to one of the lattice vibrations. The decay time of this luminescence band is 1.0 ms. 相似文献