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1.
D. Zhang G. Lan X. Chen D. Zhu 《Applied Physics A: Materials Science & Processing》2002,74(2):265-272
An X-ray powder diffraction study was performed on vapor transport equilibration (VTE) treated Er:LiNbO3 crystals with different doping levels (0.2, 0.4 and 2.0% Er per cation site), different cut orientations (X- and Z-cuts)
and different VTE durations (120, 150 and 180 h). Their diffraction characteristics were compared with those of pure congruent
LiNbO3 and as-grown Er:LiNbO3. The most significant characteristic is the appearance of additional weak and broad peaks around the 2θ angles 30° and 59°
in the diffraction patterns of both X- and Z-cut 2.0 mol% doped VTE crystals, confirming that they precipitated. A further
comparison of their diffraction data with the powder diffraction files indicated that the new phase in these precipitated
crystals is ErNbO4, which has an approximate concentration of 1.0%, 1.065%, 1.485% for 120, 150 and 180 h crystals, respectively. The crystalline
grain sizes of the new phase are 132.2∼184.1?. The unit cell parameters of the as-grown and VTE crystals were also determined
from diffraction data; the variation from pure LiNbO3 to as-grown Er:LiNbO3 was qualitatively explained according to the crystal structure of LiNbO3 and using the concept of ionic radius. VTE brings the crystal closer to a stoichiometric composition, thus causing the contraction
of the lattice constants. Finally, a tentatively qualitative explanation for precipitate formation is given on the basis of
crystal structure.
Received: 2 August 2000 / Accepted: 29 March 2001 / Published online: 20 June 2001 相似文献
2.
I. Savova I. Savatinova P. Kircheva E. Liarokapis 《Applied physics. B, Lasers and optics》2001,73(5-6):565-568
In this work we present polarized Raman measurements of z-cut multimode H:LiNbO3 waveguides in the κi- and βi-phase states. A spectrum with unexpected form and behaviour, originating from the layer at the very surface, was observed
in samples with various degrees of Li–H substitution. Possible reasons for the presence of this strange spectrum are considered.
Received: 16 May 2001 / Revised version: 7 August 2001 / Published online: 23 October 2001 相似文献
3.
The BaW04-17 phase is synthesized at 5.0 GPa and 610~C with a cubic-anvil apparatus and identified by XRD. Raman scattering measurement is carried out to investigate the phase behaviour of a pure BaW04-Ⅱ phase (space group P21/n, Z = 8) under hydrostatic pressures up to 14.8 GPa at ambient temperature. In each spectrum recorded for this phase, 27 Raman modes are observed, and all bands shift toward higher wavenumber with a pressure dependence ranging from 3.8 to 0.2 cm- 1/GPa. No pressure-driven phase transition occurs in the entire pressure range in this study. Our results indicate that the previously reported high pressure phase of Ba WO4 at pressure above about 10 GPa and room temperature (Errandonea et al. Phys. Rev. B 73(2006)224103) is not the BaW04-Ⅱ phase. 相似文献
4.
X. L. Wu M. S. Zhang Q. Chen D. Feng 《Applied Physics A: Materials Science & Processing》1995,60(3):317-320
E(TO)-mode properties in LiTaO3:Nd crystal were examined by analyzing the Raman spectra measured.E(TO) modes appear in the transverseA
1 spectrum. Their intensities obviously increase in theE andE+A
1 mixed-symmetry spectra but decrease in theE spectrum which shows new vibrational modes. In particular, in the transverse-E spectrum of y(xz)
geometry, the properties ofE(TO) modes are similar to those of pure LiTaO3 of the same geometry, whereas in the transverse-E spectrum in x(yz)
geometry these modes are turned intoA
1 (TO) modes. We attribute these properties to both the surface strain produced by mechanical polishing of the sample and the microstructural change of the LiTaO3 crystal resulting from Nd doping. 相似文献
5.
Synthesis and Raman characterization of mono-sized single-wall carbon nanotubes in one-dimensional channels of AlPO4-5 crystals 总被引:1,自引:0,他引:1
H.D. Sun Z.K. Tang J. Chen G. Li 《Applied Physics A: Materials Science & Processing》1999,69(4):381-384
Mono-sized single-wall carbon nanotubes were formed in one-dimensional channels of AlPO4-5 single crystal (AFI) by pyrolysis of tripropylamine (TPA). Raman spectra have been measured for the TPA-AFI crystals thermally
processed at different conditions. TPA molecules are carbonized at 400 °C, and carbon nanotubes were formed at 500 °C or above.
The radial-breathing mode, which is special for carbon nanotube geometry, was observed. Three Raman-active modes with symmetry
A
1g, E
1g, and E
2g were identified by detailed symmetrical analysis for the polarized-Raman spectra.
Received: 29 October 1998 / Accepted: 29 March 1999 / Published online: 24 June 1999 相似文献
6.
Olga Degtyareva Viktor V. Struzhkin Russell J. Hemley 《Solid State Communications》2007,141(3):164-167
The vibrational dynamics of elemental solids that form incommensurate host-guest structures are of fundamental interest. High-pressure Raman scattering has been used to examine the vibrational spectrum of the group-V element Sb up to 33 GPa. A1g and Eg phonons of the ambient pressure rhombohedral A7 phase display a marked decrease with pressure, i.e., prior to the transition to the tetragonal host-guest Sb-II phase at 8.6 GPa, via the monoclinic host-guest Sb-IV phase. The Raman spectrum of the incommensurate host-guest Sb-II phase, has five bands between 80 cm−1 and 200 cm−1 that increase with pressure. For the bcc structure stable above 28 GPa, we observe one weak disorder-induced band that increases with pressure. 相似文献
7.
B. Sundarakkannan R. Kesavamoorthy 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):179-183
Raman scattering from oriented single crystals of BaFCl was recorded at various temperatures from 20 to 1073 K for the first
time. The Raman spectra, corrected for phonon population, were fitted to the sum of four Lorentzian peaks. The peak frequencies
and full width at half maximum (FWHM) of the peaks were obtained from the fit. The FWHM is accounted for by cubic and quartic
anharmonic processes. The quartic anharmonicity of the mode increases with the mode frequency. The quartic anharmonicity of
the fluorine mode is exceptionally high. The peak frequencies decrease linearly with the increasing temperature. Fluorine
mode frequencies decrease more than the internal mode frequencies do. The LO-TO splitting of the fluorine modes and that of
the internal modes increases with temperature indicating the increase of the ionic bonding character. The results are discussed.
Received: 12 May 1997 / Accepted: 25 July 1997 相似文献
8.
V. Uhl K.O. Greulich S. Thomas 《Applied Physics A: Materials Science & Processing》1997,65(4-5):457-462
′ and NBOH). Samples with high OH content exhibit gradual recovery from the absorption band within several minutes after exposure
to the KrF laser radiation.
The formation of the KrF laser-induced 210 nm absorption band depends on the fictive temperature and on the OH content. Low
fictive temperature, as a measure for the number of intrinsic defects, retards E′ generation at the beginning of intense KrF excimer laser irradiation when the majority of defects are generated from precursor
defects. However, for longer irradiation periods with pulse numbers of the order of 105 pulses, a high OH content is the beneficial parameter. The accompanying atomic hydrogen is essential for the suppression
of the 210 nm absorption band. This happens by transformation of the E′ centers into Si-H defects.
In contrast to a generally held view, annealing (decreasing of the fictive temperature) of fused silica does not always reduce
UV induced defect generation. For example, annealing of the samples in an argon atmosphere causes a significantly higher 210 nm
absorption increase during KrF excimer laser irradiation (240000 pulses) compared to nonannealed samples.
Two spectroscopic methods to determine the OH content of fused silica were applied: Raman and infrared spectroscopy, which
in this work lead to differing results.
The energetics of the 210 nm absorption band generation and bleaching is summarized by a diagram explaining the interaction
of the 248 nm laser radiation with fused silica.
Received: 2 June 1997/Accepted: 13 June 1997 相似文献
9.
F. Lanciotti Jr. P.S. Pizani C.E.M. Campos E.R. Leite L.P.S. Santos N.L.V. Carreño E. Longo 《Applied Physics A: Materials Science & Processing》2002,74(6):787-789
Raman scattering and photoluminescence (PL) studies on milled PbTiO3 are presented in this paper. The results suggest that the visible PL emission could be related to both the localized states
in the interface between the amorphous layer and the crystalline core and the amorphous layer itself. The Raman spectrum of
PbTiO3 milled for a long time showed the vibrational density of states, and a detailed analysis of the soft mode allowed us to conclude
that the PbTiO3 crystalline core did not experience any structural phasetransition.
Received: 2 February 2001 / Accepted: 23 July 2001 / Published online: 17 October 2001 相似文献
10.
In the present work the fabrication of high-quality LiNbO3 waveguides, based on Zn diffusion from vapor phase using a two-step diffusion process, has been demonstrated. The optical
waveguides fabricated using this method have low propagation losses (less than 0.5 dB/cm measured at 633 nm), as a consequence
of the high surface quality obtained. High photorefractive damage resistance is reported, and it has been related to the Zn
incorporation into the LiNbO3 crystals. Additional advantages of this waveguide fabrication method due to the low temperature of the process (<900 °C)
are to prevent Li out-diffusion and to preserve ferroelectric domain structures.
Received: 2 March 2000 / Accepted: 21 June 2000 / Published online: 13 September 2000 相似文献
11.
Structural and optical properties of nanophase zinc oxide 总被引:7,自引:0,他引:7
Y. Du M.-S. Zhang J. Hong Y. Shen Q. Chen Z. Yin 《Applied Physics A: Materials Science & Processing》2003,76(2):171-176
Nanophase zinc oxide samples were synthesized by a two-step solid-state reaction method. The phase structure and microstructure
were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The vibrational Raman spectra were
compared with those from the bulk and their grain size dependence was also examined. Their photoelectric behavior was studied
by X-ray photoelectron spectroscopy (XPS). The peaks at 1044.5 and 1021.4 eV were recorded as corresponding to the respective
binding energies of Zn 2p1/2 and Zn 2p3/2, and the photoelectron spectrum of O 1s in the as-prepared powder was located at 531.2 eV. A strong visible emission centered
at 580 nm was clearly observed in the nanosized zinc oxide at room temperature. Photoluminescence (PL) spectra were investigated
as a function of grain size after different heat treatments. The origin of the luminescence is attributed to the recombination
of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band.
Received: 30 June 2001 / Accepted: 20 February 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +86-25/359-5535, E-mail: mszhang@nju.edu.cn 相似文献
12.
Raman spectra of phosphorous doped ZnSe are recorded from 9 to 300 K. In addition to TO mode at 208 cm−1 and LO mode at 253 cm−1, a new mode around 240 cm−1 is observed between 55 and 270 K. The spectra at lower and higher temperatures do not show the new mode. This new mode confirms that there is a reduction of (Se site) symmetry from Td to C3v when P substitutes for Se. This is due to Jahn Teller distortion. 相似文献
13.
Yu.N. Korkishko V.A. Fedorov S.M. Kostritskii 《Applied physics. B, Lasers and optics》1998,67(5):577-581
i -HxLi1-xNbO3 phases generated on x-cut LiNbO3 the new anisotropic libration mode at 890–940 cm-1 is observed in addition to the known isotropic mode at 960–970 cm-1, whereas the same phases on z-cut exhibit only latter isotropic libration mode. The observed phenomena are explained as a result
of anisotropic stresses generated in the x-cut waveguides, whereas the stresses in the structures on z-cut are isotropic.
The OH-bond librations are clearly anisotropic in the α, κ1, and κ2 phases generated on both z- and x-cuts, which indicates a fundamental difference of the local symmetry of the proton’s position
in the βi phases compared to the α, κ1, and κ2 HxLi1-xNbO3 phases.
Received: 4 May 1998/Revised version: 26 June 1998 相似文献
14.
A comparative study of the properties of two highly ordered lead based complex perovskites Pb(Y b1/2Ta1/2)O3 and Pb(Y b1/2Nb1/2)O3 has been carried out through x-ray diffraction, dielectric and Raman scattering measurements. These two compounds differ significantly in their structure, dielectric response and phonon vibration although the ionic radii and valencies are same for Ta and Nb. The room temperature x-ray diffraction pattern and Raman spectra show that the symmetry of lead ytterbium tantalate is lower than that of lead ytterbium niobate. The Raman spectra of Pb(Y b1/2Ta1/2)O3 also indicates the presence of local distortion in the lattice which may be one of the factors responsible for the existence of a secondary transition. 相似文献
15.
I. Sokólska 《Applied physics. B, Lasers and optics》2000,71(2):157-162
LaGaO3 crystals doped with Er3+ ions were grown by the Czochralski method and their optical properties were examined. The Er3+ energy levels have been determined from the low-temperature absorption and emission spectra. The results of Judd–Ofelt analysis
are presented and compared with experimental data. The emission cross sections are determined for the 4
I
13/2→4
I
15/2 (1.55 μm) and 4
I
11/2→4
I
13/2 (2.85 μm) transitions of erbium.
Received: 6 December 1999 / Revised version: 10 February 2000 / Published online: 27 April 2000 相似文献
16.
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
17.
V. Dierolf A.B. Kutsenko C. Sandmann F. Tallian W. von der Osten 《Applied physics. B, Lasers and optics》1999,68(5):767-775
Detailed excited state absorption measurements under pumping at 980 nm and 1.5 μm together with conventional absorption and
emission spectroscopy is employed to investigate optical transitions of Er3+ in Ti:LiNbO3 channel-waveguides. The experimental data were evaluated using the Judd–Ofelt method giving parameters close to those in
the bulk. The good agreement between theoretical prediction and measurements allows us to calculate cross section, lifetimes,
and branching ratios. Based on these results we developed and tested a model which is able to predict the conditions for which
laser operation at 550 nm and 2.7 μm will be possible under 980 nm pumping.
Received: 9 December 1998 / Revised version: 8 January 1999 / Published online: 24 March 1999 相似文献
18.
D. Porezag G. Jungnickel T. Frauenheim G. Seifert A. Ayuela M.R. Pederson 《Applied Physics A: Materials Science & Processing》1997,64(3):321-326
\chem{[C_{60}]_{\chemindex{n}}} -oligomers (, , and ) as well as dimers partially bridged by oxygen atoms or a group. The applicability of the scheme for finding the ground state of these systems was carefully checked against more sophisticated
methods including an all-electron, self-consistent (SCF) scheme based on the local-density-approximation (LDA), and the recently
developed generalized-gradient approximation (GGA). We present Raman intensities for the vibrations of the oligomers, obtained in the framework of the bond polarization model, and compare with recent experimental data.
Received: 26 September 1996/Accepted: 16 December 1996 相似文献
19.
4 Ti3O12. Basic properties of absorption gratings in this crystal are investigated with beam-coupling experiments. Depending on the
grating spacing, wavelength, and intensity of the writing beams, an absorption grating in our sample can be either in phase
or shifted by 180° with respect to the light pattern. The formation mechanism of absorption grating is discussed and proposed
to originate from a shallow-trap effect.
Received: 10 February 1997 相似文献
20.
V. Dierolf A.B. Kutsenko A. Ostendorf Chr. Sandmann 《Applied physics. B, Lasers and optics》2001,73(5-6):443-448
In order to elucidate the interaction effects among the various defects present in a LiNbO3-based integrated optical device, we investigated the change of the optical properties of Er3+ ions under the application of an external electric field and hydrostatic pressure. We obtained for stoichiometric bulk material
a complete picture of the field-induced spectral shifts as a function of transition and site. As a first important application
of these results we were able to clarify the mechanism of spectral broadening of the Er3+ transitions in Ti:Er:LiNbO3 channel waveguides. By selecting different waveguide modes for excitation and using highly selective double-resonance excitation
with two lasers, we found that the [Ti4+] concentration gradient caused by the indiffusion results in an internal E-field gradient. This translates, due to the averaging
within the guided mode, into mode-dependent spectral line broadening.
Received: 24 May 2001 / Published online: 23 October 2001 相似文献