共查询到20条相似文献,搜索用时 15 毫秒
1.
D.L. Zhang J. Zhang Y.F. Wang E.Y.B. Pun 《Applied Physics A: Materials Science & Processing》2005,81(5):1009-1018
Raman spectra of as-grown and reduced (or annealed) Er:LiNbO3 crystals, which have different cut orientations, varied Li/Nb ratio, and different Er-doping levels of 0.2, 0.4, 0.6, 1.0, and 2.0 mol%, were recorded at room temperature over a wavenumber range of 50–1000 cm-1 by use of backward scattering geometries. The spectra are assigned on the basis of their Raman scattering features and previous relevant work. A weak but well-resolved peak around 633 cm-1 appears in the E(TO) spectra that were recorded under the configuration of X(ZY)X̄(for an X-cut sample) or Y(ZX)Ȳ(for a Y-cut sample) for all crystals studied. The appearance of this peak in the E(TO) spectrum provides further evidence for a previous attribution of this peak to E(TO9) mode. Some additional peaks distributed in the low wavenumber region ranging from 101–137 cm-1 are attributed to Er3+ fluorescence with a wavelength range of 490.41–491.3 nm. The reduction effects include a significant drop of the Raman scattering intensity and a slight narrowing instead of a broadening in the linewidth. The reduction procedure hardly affects the spectral shape and the wavenumber of most of the phonons. The anneal effect is similar to the reduction effect and both effects are not as obvious as the vapor transport equilibration (VTE) effect. In addition, the present Raman scattering result provides evidence for our earlier reported individual result on light-induced diffraction from strongly reduced Er:LiNbO3 crystals. PACS 42.70.Hj; 81.05.-t; 63.20.-e; 78.30.-j. 相似文献
2.
K. Chah M.D. Fontana M. Aillerie P. Bourson G. Malovichko 《Applied physics. B, Lasers and optics》1998,67(1):65-71
3 along the ferroelectric c axis in pure and chromium-doped crystals. We have studied four series of samples with various crystal
compositions and doping concentrations to separate the influence of the intrinsic defects related to the non-stoichiometry
and the effect of the introduction of chromium. In pure and slightly doped crystals, the electro-optic coefficient rc shows a non-monotonous dependence on the controlled crystal composition, which reflects a similar behaviour of the corresponding
dielectric permittivity. In the highly Cr-doped crystals rc displays a large decrease with increasing Cr concentration whatever the crystal composition. The results have been discussed
by means of the LiNbO3 structure and the substitution site dynamics.
Received: 14 November 1997/Accepted: 2 January 1998 相似文献
3.
Fast photorefractive response in strongly reduced near-stoichiometric LiNbO(3) crystals 总被引:3,自引:0,他引:3
The photorefractive response time of LiNbO(3) crystal is of the order of minutes, and such a long response time limits the crystal's practical applications. We report the photorefractive properties of nominally pure near-stoichiometric LiNbO(3) crystal that is strongly reduced in vacuum. A short photorefractive response time of the order of 100 ms is measured at a wavelength of 514.5 nm, with incident light intensity of 1.6 W/cm (2) , and possible corresponding mechanisms are discussed. To our knowledge this is the first experimental evidence of a subsecond photorefractive response in pure LiNbO(3) crystals. The diffraction efficiency of a holographic grating written in this reduced crystal is low but can be enhanced by an externally applied electric field. 相似文献
4.
D.-L. Zhang J. Zhang Z.-K. Wu E.Y.B. Pun 《Applied Physics A: Materials Science & Processing》2006,83(3):397-409
Light-induced absorption (LIA) in thermally reduced congruent and near-stoichiometric Er:LiNbO3 crystals, which have different cuts of crystal (X- and Y-cut) and different doping levels of Er3+ (0.2, 0.4, 0.6 and 1.0 mol %), has been studied within continuous-wave light intensity by using polarized 632.8 nm beam as
probe light and polarized 488 nm beam as pump light. Effects of thermal reduction condition, pump intensity, Li/Nb ratio and
Er-doping level on the LIA are summarized and discussed. Studies on spectral characteristics of both linear absorption and
light-induced absorption show that photo-ionization of bipolarons into small polarons plays a predominant role in the LIA
process. The role of the Er3+ ion in the LIA is investigated by studying the doping level and the thermal reduction effects on the absorption and emission
properties of Er3+. The results show the possibility that the Er3+ ion directly participates in the light-induced charge transport is small. It affects the LIA only via the bypassing part
of pump intensity to excite near-infrared emissions of Er3+. The thermaleffect on the LIA is demonstrated. A two-center model with inclusion of the thermal contribution can qualitatively
explain two major LIA characteristics that include the appearance of a slow stage in the LIA procedure and the unsaturation
behavior of the LIA coefficient in high pump intensity regime. In addition, the pump depletion effect on the LIA characteristics
is discussed. The possibility of pump beam fanning arising from light-induced scattering is ruled out experimentally.
PACS 42.70.Hj; 42.70.Ln; 42.70.Mp; 42.65.Hw; 81.05.-t 相似文献
5.
Lei Zhong Zhanguo Wang Shouke Wan Jinbin Zhu F. Shimura 《Applied Physics A: Materials Science & Processing》1992,55(4):313-316
Neutron transmutation doped (NTD) silicon crystals grown in a hydrogen atmosphere have been investigated by infrared absorption spectroscopy at a low temperature (10 K). An effective-mass-like donor state HD0/+ has been found at 110.8 meV below the conduction band bottom after rapid thermal annealing (RTA). The HD0/+ formation mechanism after NTD and RTA is briefly discussed, and tentatively attributed to H atoms present in the vicinity of some residual irradiation defects, like a complex of a H atom and a H-saturated vacancy. 相似文献
6.
E. Camarillo H. Murrieta J.M. Hernandez R. Zoilo M.C. Flores T.P.J. Han F. Jaque 《Journal of luminescence》2008,128(5-6):747-750
Lithium niobate (LiNbO3) crystals doped with chromium ions show a clear green colouring reflecting the absorption profile of the dominating [Cr]Li defect centres. A significant change in its colouration takes place when it is co-doped with other valency impurities such as Mg2+, Sc3+ and W6+, above a certain threshold concentration. This concentration singularity has been attributed to the formation of [Cr]Nb centres coexisting with the [Cr]Li centres.In this work, we extended the investigation on the effect of co-dopant ions in Cr:LiNbO3 to tetravalent cation such as GeO2. A singularity in the relative intensity of the 4A2→4T1 and 4A2→4T2 absorption band was observed for a concentration of ~1.5 mol%, compared with 4.5 mol% for Mg2+. The photoluminescence emission spectra also reveal a new emission band, at a lower energy than the [Cr]Li centre, corresponding to this threshold concentration. A charge compensation model is proposed to explain the role of cation impurities and results are compared with those of other valence impurities. 相似文献
7.
A. A. Berezhnoĭ 《Optics and Spectroscopy》2002,92(3):459-464
Results of studying the conditions for optimum electrooptical (EO) interaction in lithium niobate crystals are presented. Analytical formulas are obtained for calculating refractive indices of natural waves and their polarizations for basis X-, Y-, and Z-cuts of crystals for arbitrary orientations of the wave vector of an optical wave. Conditions are found for the appearance of intermode EO interaction causing the orientation of polarization plane of natural waves to become a function of the external electric field. 相似文献
8.
从光折变效应的单中心模型和载流子的光伏迁移机理出发给出了高斯片光在LiNbO3:Fe晶 体中导致的折射率变化分布的解析表达式.利用片光以“三明治”辐照方式在LiNbO3:Fe晶 体中写入了平面光波导结构.用切片干涉法测量了波导区的折射率分布,并对波导进行了简 单的导光测试.根据射线方程以及波导的折射率分布对光写入波导的导光特性进行了模拟计 算分析.研究结果表明,在LiNbO3:Fe晶体中光写入光波导是可行的.
关键词:
LiNbO3:Fe晶体
光辐照法
平面光波导
导光特性
高斯片光 相似文献
9.
A series of Zr:Fe:LiNbO3 crystals with various levels of ZrO2 doping were grown by Czochraski technique. The optical damage resistance and photorefractive properties were deeply explored. The results showed that the ability optical damage resistance increased remarkably when the concentration of ZrO2 is over threshold concentration, but which is lower than that of traditional damage resistant additive MgO. While, the holographic storage properties can be greatly enhanced by proper level of ZrO2 doping in Fe:LiNbO3. In terms of ions' site occupation model, the photo-damage resistant ability enhancement and the change of the photorefractive properties were discussed. 相似文献
10.
This paper describes a new way of recording information by changing the potential contour at the surface of z-cut crystals of LiNbO3. The effect of various kinds of external perturbations on the rate of decay of optical images written using this method is
investigated, along with the possibility of writing information on crystals with transition-metal impurities.
Fiz. Tverd. Tela (St. Petersburg) 40, 337–339 (February 1998) 相似文献
11.
12.
T. Volk B. Maximov T. Chernaya N. Rubinina M. Wöhlecke V. Simonov 《Applied physics. B, Lasers and optics》2001,72(6):647-652
LiNbO3:Zn single crystals and powders were studied by precise X-ray diffraction methods. Structural refinement yielded new models
of the intrinsic defect structure valid for different Zn concentration ranges. For concentrations up to 7 at. % in the crystal,
Zn ions incorporate onto Li sites; at higher concentrations Zn ions are found on both Li and Nb sites. Photorefractive properties
of LiNbO3:Zn are discussed in the context of the deduced defect models. A smooth increase in the photoconductivity up to 7 at. % Zn
is accounted for by a decrease of Nb antisites. Steeper growth of the photoconductivity at higher Zn concentrations is related
to vanishing Li vacancies.
Received: 17 November 2000 / Revised version: 23 January 2001 / Published online: 20 April 2001 相似文献
13.
The LiNbO3 crystal co-doped with ZrO4 and Fe2O3 has been grown with [Li]/[Nb]=0.85 and 1.20, respectively, by the Czochralski method in air atmosphere. The incident exposure energy flux threshold for the light-induced scattering was characterized to investigate the scattering properties of the crystals. Applying the results of the incident exposure energy flux threshold effect, the photorefractive properties at different laser wavelengths (473 nm and 532 nm) were also measured by using the typical two-wave coupling experiments. The results show that Zr:Fe:LiNbO3 crystal has a larger refractive index change, higher recording sensitivity and larger two-wave coupling gain coefficient at 473 nm wavelength than those obtained at 532 nm wavelength under the same experimental conditions. Moreover, the photorefractive properties decrease with the increasing [Li]/[Nb] ratios. The material of Zr:Fe:LiNbO3 crystal is a promising candidate for blue photorefractive holographic recording. 相似文献
14.
15.
A series of LiNbO3 crystals doped with various concentrations of ZnO and fixed concentrations of RuO2 and Fe2O3 have been grown by the Czochralski method from the congruent melts. The type of charge carriers was determined by Kr+ laser (476 nm) and He–Ne laser (633 nm). The results revealed that the holes were the dominant charge carriers at blue light irradiation. Dual-wavelength and two-color techniques were employed to investigate the nonvolatile holographic storage properties of Ru:Fe:LiNbO3 and Zn doped Ru:Fe:LiNbO3 crystals. The essential parameters of blue nonvolatile holographic storage in Zn:Ru:Fe:LiNbO3 crystals were enhanced greatly with the increase of Zn concentration. This indicates that the damage resistant dopants Zn2+ ions enhance the photorefractive properties at 476 nm wavelength instead of suppressing the photorefraction. The different mechanisms of blue photorefractive and nonvolatile holographic storage properties by dual wavelength recording in Zn:Ru:Fe:LiNbO3 crystals were discussed. 相似文献
16.
The time dependence of the photorefractive light scattering in lithium niobate single crystals of the congruent composition
(LiNbO3) doped by “photorefractive” Cu cations (0.015 wt %) is studied for a radiation power of 160 mW. The data for the photorefractive
scattering are confirmed by changes in Raman scattering spectra. 相似文献
17.
A new hydrogen associated paramagnetic centre (g=2.0028±0.0005, A=3±0.5 mT at 77K) was observed in LiNbO3. This centre is identified as an OH2? ion, produced as a result of an electron capture by a diamagnetic OH? ion, substituting the O2? ion in LiNbO3. An experimental procedure for detecting the EPR spectrum of the new centre is established. It is based on the observation of the more rapid destruction of O? and Nb4+ ions under UV-irradiation at 77 K as compared to the OH2? ions obtained after γ-irradiation of LiNbO3 crystals at 77 K. 相似文献
18.
O. Momtahan G.H. Cadena A. Makhmalbaf A. Adibi 《Applied physics. B, Lasers and optics》2008,90(3-4):519-525
In this paper, we report the observation of electron tunneling during two-center recording in LiNbO3:Fe:Mn doped with high Fe concentration. Unlike tunneling in the singly doped lithium niobate that erases the hologram, the
effect in two-center recording can improve the diffraction efficiency of the hologram after the recording while it is kept
in the dark. A detailed study of this effect in LiNbO3:Fe:Mn is presented both theoretically and experimentally. We show that the hologram strength may increase or decrease due
to tunneling, depending on the experimental condition of recording.
PACS 42.40.-i; 42.70.Ln; 42.40.Lx 相似文献
19.
对用助熔剂提拉法生长的近化学计量比LiNbO3晶体进行了激光显微拉曼光谱测试分析,与同成分LiNbO3晶体相比较,A1(TO)与E(TO)模的谱线数目、频率基本不变,验证了LiNbO3晶体属置换式固溶体的结论.738cm-1处拉曼振动峰(A1(LO)模)的相对强度随晶体中Li2O含量的增加发生了明显的变化,在两种掺杂晶体中,此振动峰已经消失.根据Li空位模型,从占位和结构上进行了分析讨论.在152和872cm-1处拉曼振动峰半高宽随晶体中Li/Nb的增大而变窄,对二者关系进行了线性拟合,利用拟合公式可根据拉曼振动峰半高宽计算晶体中的Li/Nb值.
关键词:
化学计量比
拉曼光谱
线性拟合
半高宽 相似文献
20.
R. Hammoum M.D. Fontana M. Gilliot P. Bourson E.P. Kokanyan 《Solid State Communications》2009,149(43-44):1967-1970
By means of Raman scattering spectroscopy we determine the site location occupied by Hf ions in photorefractive damage resistant Hf-doped LiNbO3. At room temperature the two lowest frequency phonons are related to sites B (Nb) and A (Li), and are used to directly probe the dopant ion. For the low concentration range, the Hf ions go into the sites A whereas, for high concentration, Hf ions occupy both sites A and B. Results are compared with data obtained for pure congruent and stoichiometric crystals, and the proposed mechanism of incorporation of Hf ions in the LiNbO3 lattice explains the threshold in the behaviour of photorefractive properties. 相似文献