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1.
R. Nevado C. Sada F. Segato F. Caccavale A. Kling J.C. Soares E. Cantelar F. Cussó G. Lifante 《Applied physics. B, Lasers and optics》2001,73(5-6):555-558
Rutherford backscattering (RBS) and secondary-ion mass spectrometry techniques have been used to investigate the two-step
process involved during waveguide fabrication in LiNbO3 using Zn-vapour diffusion. Compositional analysis (O, Nb, Li and Zn) in the two steps has been characterised. RBS analysis
reveals that the first step, involving a heating of the substrate under a metallic Zn atmosphere, gives rise to a partial
exchange between the Nb and Li ions from the crystals and the Zn from the vapour source. The second treatment at higher temperature
in an open atmosphere diffuses the Zn deeper into the substrate, thus forming an optical waveguide, while the Nb and Li ions
recover their bulk values.
Received: 16 May 2001 / Revised version: 7 September 2001 / Published online: 30 October 2001 相似文献
2.
Influence of Zn doping on electrooptical properties and structure parameters of lithium niobate crystals 总被引:1,自引:0,他引:1
F. Abdi M. Aillerie M. Fontana P. Bourson T. Volk B. Maximov S. Sulyanov N. Rubinina M. Wöhlecke 《Applied physics. B, Lasers and optics》1999,68(5):795-799
We report the dependence of the unit cell parameters and the EO coefficients on Zn doping in optical-damage-resistant LiNbO3:Zn crystals. Both properties depend in a non-monotonic manner on the Zn content. This is accounted for by different types
of Zn ion incorporation into the lattice depending on the Zn concentration in the melt. Extrema observed in the concentration
dependence of the EO coefficients at about 2–3 and 6.4 mol.% Zn correlate with an unusual concentration dependence of the
unit cell parameters a and c. The low-concentration anomalies may be accounted for by a decrease of the Li vacancy concentration
due to the Zn incorporation into Li sites. Anomalies at high concentrations are obviously due to a partial incorporation of
Zn ions on Nb sites, which is reflected in the structure data. Anomalies in the concentration dependence of other optical
properties at about 6–7 mol.% Zn reported recently are obviously related to a change in the localization of the Zn ions.
The combination of high EO coefficients with a reduced optical damage for these concentrations make these crystals attractive
for applications as Q-switching or electrooptical modulation.
Received: 16 Nowember 1998 / Revised version: 8 December 1998 / Published online: 24 March 1999 相似文献
3.
A series of Zn: In: Fe: LiNbO3 crystals are grown by the Czochralski technique with various ratios of Li/Nb = 0.94, 1.05, 1.20 and 1.38 in the melt. The Zn, In, Fe, Nb and Li concentrations in the crystals are analyzed by inductively coupled plasma (ICP) spectrometry. The results indicate that with increasing the [Li]/[Nb] ratio in melt, [Li]/[Nb] ratio increases and goes up continuously in the crystal, the segregation coefficients of both Zn and In ions decrease. The absorption spectra measurement and two-wave coupling experiment are employed to study the effect of [Li]/[Nb] ratio on photorefractive properties of Zn: In: Fe: LiNbO3 crystals. It is found that the [Li]/[Nb] ratio increases, the write time is shortened and the photorefractive sensitivity is improved. 相似文献
4.
Energy Dispersive X-ray Fluorescence Spectroscopy, X-ray diffraction and density measurements were conducted on undoped and ZnO-doped congruent LiNbO3 single crystals grown by the Czochralski method. Based on the experimental results, an intrinsic defect evolution model was proposed. When ZnO was doped into the congruent LN crystals, the Zn ions replaced first the Li ions and increased the density. Then, the Zn ions simultaneously replaced the Li ions and the antisite NbLis until all NbLi ions were replaced, which increased the density further. After that, the Zn ions substituted Nb ions in the Nb-sublattice sites with the reduction of the Li vacancies as self-compensation and thus reduced the density. When the Li vacancies disappeared completely, the Zn ions substituted simultaneously both Li ions in the Li-sublattice sites and Nb ions in the Nb-sublattice sites. The simultaneous substitution might finally lead to the generation of oxygen vacancies and decreased the density further. PACS 61.72.-y; 06.30.Dr; 61.10.-i 相似文献
5.
A series of Zn:Fe:LiNbO3 crystals were prepared by the Czochralski technique with 0.015 wt. % Fe2O3 content and various concentrations of ZnO. The ultraviolet-visible absorption spectra and the infrared absorption spectra
of the Zn:Fe:LiNbO3 crystals were detected in order to investigate their defect structure. Their optical damage resistance was characterized
by the photoinduced birefringence change and transmission facula distortion method. The optical damage resistance of the Zn:Fe:LiNbO3 crystals increases remarkably when the concentration of ZnO is over its threshold concentration (more than 6.0 mol. %). The
effects of defects on the optical damage resistance of the Zn:Fe:LiNbO3 crystals are discussed in detail.
Received: 25 October 2002 / Revised version: 6 January 2003 / Published online: 22 May 2003
RID="*"
ID="*"Corresponding author. Fax: +86-451/2300-926, E-mail: zzxxhhdoctor@sina.com 相似文献
6.
Huixian Feng Jinke Wen Hong Wang Huafu Wang 《Applied Physics A: Materials Science & Processing》1990,51(5):394-397
The absorption spectra, photoconductivities and photovoltaic currents of LiNbO3:Fe crystals with different Mg doping levels and Li/Nb ratios in the oxidized state have been investigated at room temperature. The Fe2+ ions in LiNbO3:Mg:Fe with Mg content above a critical value are more easily oxidized than in crystals with Mg content below a critical value. The photoconductivity of LiNbO3:Mg:Fe crystals with Mg content above a critical value is one order of magnitude higher than those with Mg content below a critical value, however, the photovoltaic current of the former is one order of magnitude lower than the latter. The differences are postulated to be due to different sites of Fe in these two classes of crystals. 相似文献
7.
K. Lengyel L. Kovács Á. Péter K. Polgár G. Corradi 《Applied physics. B, Lasers and optics》2007,87(2):317-322
LiNbO3:Mg crystals doped with 0–8 mol. % Mg with stoichiometric, intermediate and congruent compositions were systematically investigated
by Raman spectroscopy in backscattering y(zx)y, y(zz)y and z(xx)z geometries. The damping was found to be a very sensitive
parameter for the characterization of the crystal composition. The half-widths of E(TO3)–E(TO9) and A
1(TO1)–A
1(TO4) bands having significant composition dependence for the undoped LiNbO3 crystals show only a weak Mg concentration dependence below the photorefractive threshold, which is a consequence of the
counteracting effect of the decreasing NbLi and increasing MgLi contents. The half-widths of the bands, however, increase linearly with growing Mg content for samples above the threshold,
irrespective of the Li/Nb ratio. The change in the Mg concentration dependence at a given Li/Nb ratio determines the same
threshold value as that concluded from IR and UV spectroscopic measurements. The half-width of the main A
1(LO4) band at 873 cm-1 increases linearly with growing Mg concentration, but no threshold effect is observed. However, the ratio of the area of
the main band and the high-frequency sideband shows a threshold effect that can be interpreted by the existing defect incorporation
models. The small Raman band at about 740 cm-1 attributed earlier to NbLi vibration is also detected in above-threshold LiNbO3:Mg crystals, which can be explained by the vibration of Nb ions in Mg4Nb2O9 defect clusters appearing at high Mg concentrations.
PACS 77.84.Dy; 63.20.Mt; 42.70.Mp; 78.30.-j 相似文献
8.
Improvement of photorefractive properties in Hf:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios
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Photorefractive properties of Hf:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recording sensitivity are observed and explained. The decrease in Li vacancies is suggested to be the main contributor to the increase in the photoconductivity and subsequently to the induction of the improvement of recording sensitivity. The saturation diffraction efficiency is measured up to 80.2%, and simultaneously the recording sensitivity of 0.91 cm/J is achieved to in the Hf:Fe:LiNbO3 crystal grown from the melt with the [Li]/[Nb] ratio of 1.20, which is significantly enhanced as compared with those of the Hf:Fe:LiNbO3 crystal with the [Li]/[Nb] ratio of 0.94 in melt under the same experimental conditions. Experimental results definitely show that increasing the [Li]/[Nb] ratio in crystal is an effective method for Hf:Fe:LiNbO3 crystal to improve its photorefractive properties. 相似文献
9.
OH-absorption properties of the optical damage region in a series of codoped In/Mg:LiNbO3 crystals with various Li/Nb ratios have been investigated. The OH−-associated vibrational peak at 3507 cm−1 is confirmed to occur in crystals with Li/Nb ratio of 0.94. For codoped In/Mg:LiNbO3 crystals with Li/Nb ratio of 1.05 and 1.20, the OH−-associated vibrational peaks are detected at 3536 and 3507 cm−1 as well. A new peak at 3518 cm−1 attributed to a (InNb)2−-OH−-(MgNb)3− defect center is revealed in crystals with Li/Nb ratio 1.38. When the “In-Mg threshold” concentration is reached, the optical damage resistance ability of codoped In/Mg:LiNbO3 crystals is greatly improved. 相似文献
10.
Ce:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios were grown by the Czochralski method from melts having compositions varying between 48.6 and 58 mol% Li2O. The Ce, Li and Nb concentrations in the grown Ce:Fe:LiNbO3 crystals were analyzed by the inductively coupled plasma atomic emission spectrometer (ICP-AES). It was found that as the [Li]/[Nb] ratio increases in the melt, the [Li]/[Nb] ratio in the crystal and the distribution coefficients of Ce ions increase also. The photorefractive properties of the Ce:Fe:LiNbO3 crystals were experimentally studied by the two-wave coupling method. The results show that as the [Li]/[Nb] ratio increases, the dynamic range decreases, but the photorefractive sensitivity and the signal-to-noise ratio improve. In a coherent volume 0.192 cm3 of a Ce:Fe:LiNbO3 crystal with [Li]/[Nb] ratio of 1.2, 3800 holograms with 800×600 pixels have been successfully multiplexed in a compact volume holographic data storage system. 相似文献
11.
G. Schreiber H. Suche Y.L. Lee W. Grundkötter V. Quiring R. Ricken W. Sohler 《Applied physics. B, Lasers and optics》2001,73(5-6):501-504
Using an FM-mode-locked Ti:Er:LiNbO3 waveguide laser as the fundamental source, wavelength conversion by cascaded χ(2):χ(2)-difference frequency generation with a conversion efficiency of up to +3(-4.6) dB was demonstrated at a pulse repetition
rate of about 2 (10) GHz. In addition, multi-channel conversion was demonstrated with a fully packaged wavelength converter
using a continuous fundamental source.
Received: 29 May 2001 / Revised version: 10 August 2001 / Published online: 2 November 2001 相似文献
12.
T. Woike U. Dörfler L. Tsankov G. Weckwerth D. Wolf M. Wöhlecke T. Granzow R. Pankrath M. Imlau W. Kleemann 《Applied physics. B, Lasers and optics》2001,72(6):661-666
The purity and the concentrations of the constituents Sr, Ba, Nb and Cr were determined in single crystals of chromium-doped
Sr0.61Ba0.39Nb2O6 (SBN) by instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRF). Experiments with different
Cr concentrations CCr reveal constant Sr and Ba concentrations as well as a decreasing Nb concentration with an increasing CCr. Therefore, Cr is incorporated at Nb lattice sites. The distribution coefficient of Cr is 1.2 between 100 and about 7000 ppm
Cr and 1 above. From measurements of the holographic two-beam coupling gain Γ for different CCr, we deduced response times for the buildup of holographic gratings. The saturation value of Γ depends in a nonlinear manner
on CCr and reaches its maximum at about 6000 ppm Cr. The inverse photorefractive response time of the grating erasure depends linearly
on the erasure intensity for all doping concentrations. Thus a one-center model can be assumed for the charge transport in
SBN:Cr.
Received: 8 December 2000 / Revised version: 23 January 2001 / Published online: 21 March 2001 相似文献
13.
V. Dierolf A.B. Kutsenko A. Ostendorf W. von der Osten W. Sohler H. Suche 《Applied physics. B, Lasers and optics》2001,72(7):803-810
Starting from previous investigations in LiNbO3 bulk crystals, we studied the optical properties of Er3+ ions in Ti:LiNbO3 channel waveguides and investigated the waveguide-specific lattice environment of the Er3+ ions (“sites”) caused by the doping method used and the presence of a large number of Ti4+ ions. For that purpose the method of combined excitation–emission spectroscopy was applied for the first time to waveguides
at low temperatures. Comparing the spectroscopic results obtained for the green, red, and near-IR luminescence (λ≈550, ≈650
and ≈980 nm) under direct (450 nm), 2-step (980 nm), and 3-step (1.5 μm) laser excitation, we found several distinguishable
Er3+ sites which in terms of energy levels and relative numbers are similar to those in bulk material, but exhibit significantly
different up-conversion efficiencies and strongly inhomogeneously broadened transitions. Moreover, we were able to distinguish
isolated and cluster Er3+ sites by their characteristic excitation and emission transition energies and studied the respective excitation/relaxation
channels. The cluster sites are most efficient in the up-conversion process, especially under 3-step excitation. Using accepted
microscopic models for Er3+ and Ti4+ incorporation into the LiNbO3 crystal lattice, the site distribution and up-conversion mechanisms are elucidated and their consequences for laser applications
in different spectral regions are discussed.
Received: 16 November 2000 / Published online: 21 March 2001 相似文献
14.
Precision X-ray structural studies were carried out for LiNbO3:Znx single crystals with x=0.0, 2.87, 5.20, and 7.60 at. %. It was found that the insertion of the Zn atoms into the Li position was accompanied by a decrease in the concentration of intrinsic NbLi defects. At x=7.6%, the Zn atoms change their locations in the lattice and partially occupy the Nb positions. This clarifies the structural nature of the “threshold” Zn concentration, which manifests itself as singularities in the concentration dependences of various optical properties. The structural origin of the threshold concentration is likely a common feature of all nonphotorefractive impurities (Mg, Zn, In, and Sc) in LiNbO3. A change in the intrinsic defect structure of the LiNbO3 crystals with different Zn concentrations is discussed. 相似文献
15.
S.D. Cheng X.Q. Han C.H. Kam Y. Zhou Y.L. Lam J.T. Oh X.W. Xu T.C. Chong 《Applied Physics A: Materials Science & Processing》2001,73(4):511-514
We have successfully prepared highly c-axis-textured LiNbO3 films on hydrogen-terminated Si (111) substrate using sol-gel spin-coating and rapid thermal annealing. These highly c-axis-textured
films were obtained with a preheating at 300 °C for 15 min followed by a rapid thermal annealing at 500–700 °C for 120 s.
The c-axis orientation of the LiNbO3 film is due to a weak effect caused by the 3-fold symmetry match between the film and the Si (111) substrate. The c-axis
orientation of LiNbO3 films is very useful in integrated optics devices and metal–ferroelectric–semiconductor nonvolatile memory applications.
Received: 15 September / Accepted: 4 December / Published online: 3 April 2001 相似文献
16.
V.A. Fedorov Yu.N. Korkishko J.A. Sanz-García E. Cantelar R. Nevado G. Lifante F. Cussó 《Applied physics. B, Lasers and optics》2001,73(5-6):449-451
We report the dependence of the unit-cell parameters and the extraordinary and ordinary refractive indices of Er3+/Yb3+-codoped LiNbO3 crystals. Both properties depend in a non-monotonic manner on the Er3+/Yb3+ content. A singularity was observed at concentrations of 1.1-1.2 mol. % in the crystal (0.6-0.7 mol. % in the melt). In the
same way the Er and Yb concentration influences the periodically poled lithium niobate formation. The observed behavior of
refractive indices and unit-cell parameters of Er3+/Yb3+-codoped LiNbO3 crystals could be explained in terms of the RE3+-ion concentration affecting the Li-vacancy concentration and the RE3+-ion positions in the crystal.
Received: 21 May 2001 / Revised version: 22 August 2001 / Published online: 23 October 2001 相似文献
17.
Single-frequency Ti:Er:LiNbO3 distributed Bragg reflector waveguide laser with thermally fixed photorefractive cavity 总被引:1,自引:0,他引:1
The first single-frequency Ti:Er:LiNbO3 distributed Bragg reflector waveguide laser with two thermally fixed photorefractive gratings as resonator mirrors is reported.
The optically pumped (λp=1480 nm,120-mW incident power) laser emits up to 1.1 mW at λs=1561.1 nm. The threshold pump power is 70 mW.
Received: 7 June 2001 / Published online: 30 October 2001 相似文献
18.
本文报道了一组不同Li/Nb比和另一组不同掺Mg浓度的LiNbO3晶体室温OH-吸收带的实验结果,观察到OH-吸收带的三峰结构及其随Li/Nb比的变化,以及重掺Mg晶体中(6mol%MgO)OH-吸收带转变为双峰结构,并向高能端移动54cm-1。根据LiNbO3的晶体结构以及Abrahams和Smyth的缺陷结构模型,对化学计量晶体、一致熔化晶体和掺Mg晶体分别进行讨论。并提出重掺Mg晶体中OH-吸收带向高能端的移动可能是由于当掺Mg浓度超过阈值后Mg2+离子开始进入Nb位而引起的。
关键词: 相似文献
19.
Ferroelectric domain inversion in near-stoichiometric lithium niobate for high efficiency blue light generation 总被引:2,自引:0,他引:2
Y.-L. Chen J.-J. Xu X.-Z. Zhang Y.-F. Kong X.-J. Chen G.-Y. Zhang 《Applied Physics A: Materials Science & Processing》2002,74(2):187-190
LiNbO3 single crystals with a composition close to stoichiometry ([Li]/[Li+Nb]=0.496), 16 mm in diameter and 40 mm in length were
grown by the Czochralski method using K2O flux. The domain reversal characteristics of near-stoichiometric LiNbO3 single crystals were investigated. The switching field required for 180° ferroelectric domain reversal in the near-stoichiometric
crystal at room temperature was 7.5 KV/mm. This is about one third of the switching field required for conventional LiNbO3 crystals. Domain reversal (180°) in near-stoichiometric LiNbO3 samples of 1.0 mm thickness has been achieved. Samples have been evaluated by second harmonic generation and conversion efficiencies
of up to 32% have been obtained.
Received: 8 November 2000 / Accepted: 29 January 2001 / Published online: 20 June 2001 相似文献
20.
T. P. J. Han E. Cantelar G. Lifante F. Cusso F. Jaque 《Applied physics. B, Lasers and optics》2009,94(2):209-214
This paper reports on the spectroscopy properties, absorption and luminescence, of Cr3+ ions in singly doped, ZnO-codoped, and Zn in-diffused LiNbO3:Cr crystals. In addition to the broad absorption, inter-ionic transitions ascribed to Cr3+ ions located in Li+ and Nb5+ sites; [Cr]Li and [Cr]Nb centres two absorption bands at higher energy are reported and ascribed to the charge transfer transitions of the Cr3+ ions of the two defect centres.
The charge transfer transitions are used as optical probe to study the role of the Zn ions in the Zn in-diffused LiNbO3:Cr samples. It has been observed that the Zn-in-diffused processes created [Cr]Nb centres in the diffusion zone. The location of the diffused Zn2+ ions is considered to be in Li+ site, displacing the Cr3+ ions from the Li+ sites, [Cr]Li, to the Nb5+ positions, [Cr]Nb. 相似文献