共查询到20条相似文献,搜索用时 15 毫秒
1.
Qiu Y 《Physical review. B, Condensed matter》1993,48(7):4868-4870
2.
S.A. Basun A.A. Kaplyanskii A.B. Kutsenko V. Dierolf T. Troester S.E. Kapphan K. Polgar 《Applied physics. B, Lasers and optics》2001,73(5-6):453-461
Low-temperature luminescence spectra of stoichiometric Cr:LiNbO3, congruent Cr:LiNbO3 and congruent Cr,Mg:LiNbO3 were studied. Dominant low-field and minor high-crystal-field optical centers are the Cr3+ impurity ions that preferentially occupy Li+ sites (CrLi) in the Cr:LiNbO3 crystals. Low-field centers related to Cr3+ substitution of Nb5+ (CrNb) occur in addition to CrLi in co-doped Cr,Mg:LiNbO3 samples. Application of high hydrostatic pressure leads to the transformation of dominant Cr3+ centers from low- to high-field type due to strong pressure-induced blue shift of the 4
T
2 state, resulting in its crossing with the 2
E state of Cr3+. This level-crossing effect was observed for the dominant Cr3+
Li and Cr3+
Nb centers at pressures that correlate well with estimations based on the 4
T
2-2
Eenergy gap (230 cm-1 and 1160 cm-1) and on the rate of their pressure-induced change (14.35 and 11.4 cm-1/kbar, respectively). We also studied inhomogeneous broadeningof the 2
E?4
A
2transitions at ambient pressure for the minor high-field “defect” Cr3+
Li centers in congruent LiNbO3. A fine structure in the spectral response of these centers was observed. The obtained results are discussed on the basis
of a microscopic hierarchic model for perturbed Cr3+ ions in the LiNbO3 lattice.
Received: 25 June 2001 / Published online: 2 November 2001 相似文献
3.
S. A. Basun A. A. Kaplyanskii A. B. Kutsenko V. Dierolf T. Tröster S. E. Kapphan K. Polgar 《Physics of the Solid State》2001,43(6):1043-1051
Low-temperature luminescence spectra of stoichiometric Cr: LiNbO3 and of congruent Cr, Mg: LiNbO3 were studied. Cr3+ impurity ions preferentially occupy Li+ sites (CrLi) in the LiNbO3 crystal lattice, while Cr3+ ions substituting for Nb5+ ions (CrNb) occur in addition to CrLi centers in codoped Cr, Mg: LiNbO3 crystals. Application of a high hydrostatic pressure leads to a transformation of (dominant in concentration) Cr3+ centers from low-to high-crystal-field centers. Due to a strong pressure-induced blue shift of the 4 T 2 state resulting in crossing with the 2 E state, the replacement of the broad band 4 T 2 → 4 A 2 emission by a narrow R-line emission 2 E → 4 A 2 occurs in the luminescence spectra of the samples. This effect of level crossing was observed for the dominant Cr Li 3+ and Cr Nb 3+ centers at pressures which correlated well with estimations based on the 4 T 2-2 E energy gap (230 and 1160 cm?1) and on the rate of their pressure-induced change (14.35 and 11.4 cm?1/kbar, respectively). 相似文献
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6.
The effect of an external electric field on the R absorption lines of LiNbO3:Cr3+ crystals has been studied by a high-sensitivity differential technique at 77 K. Linear Stark effect has been observed in
a field directed along the trigonal crystal axis. No effect of the field was observed when directed perpendicular to this
axis. These characteristics of the Stark effect provide a convincing argument for the electric dipole moments of Cr3+ centers being oriented along the trigonal C
3 axis of the crystal and indicate that the chromium centers in LiNbO3 have C
3 symmetry.
Fiz. Tverd. Tela (St. Petersburg) 39, 2053–2056 (November 1997) 相似文献
7.
8.
M. Quintanilla E. Cantelar J.A. Sanz-García G. Lifante G.A. Torchia F. Cussó 《Journal of luminescence》2008,128(5-6):927-930
The infrared optical properties of LiNbO3 crystals doped with variable thulium concentrations have been studied. In particular, the infrared emissions that appear after direct pumping to the 3H4 multiplet (795 nm) have been analyzed. The emission spectra, as well as the lifetimes, show that an efficient energy transfer between 3F4 and 3H4 levels takes place. The concentration dependence of the lifetimes has been studied and the transfer probability has been characterized. 相似文献
9.
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
10.
《Physics letters. A》1986,117(3):150-152
In reduced LiNbO3 and ESR signal was identified which is attributed to Ti3+ (3d)1 by comparison with known (4d)1 and (5d)1 centers. The signal can be increased many times by Ti in-diffusion. It is photosensitive, being quenched by near UV-illumination. 相似文献
11.
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
12.
LiNbO3∶Cr∶Cu晶体吸收特性及非挥发全息存储研究 总被引:1,自引:1,他引:0
研究了LiNbO3∶Cr∶Cu晶体的吸收特性,发现LiNbO3∶Cr∶Cu(含0.14 wt.% Cr2O3 和 0.011 wt.% CuO)晶体存在两个明显的吸收峰,中心波长分别位于480 nm和660 nm; 随着Cr的含量逐渐减小,Cu的含量逐渐增大,短波段不存在明显吸收峰,掺Cr的含量越大,中心波长在660 nm处的吸收越大;633 nm红光虽然位于中心波长为660 nm的吸收峰内,但它无助于光折变过程.分别采用390 nm紫外光和488 nm蓝光作为敏化光,514 nm绿光作为记录光的记录方案,实现了非挥发全息记录,掺入适量的Cr( 比如NCr=2.795×1025 m-3,NCr/ NCu=1)有助于全息记录性能的提高. 相似文献
13.
U. R. Rodrigues-Mendoza V. D. Rodrigues V. Lavin I. R. Martin P. Nunez 《Journal of Applied Spectroscopy》1995,62(5):895-899
Conclusions Alkaline silicate glasses seem to be good candidates as host materials for codoping with Cr3+ and Tm3+. Cr3+ ions occupy mainly low-field sites in them, and their broadband emission overlaps Tm3+ excitation. As a consequence very high efficiency for the energy transfer Cr3+→Tm3+ is achieved with moderate concentrations of these ions. Moreover, the average lifetime of the Cr3+ ions in codoped glasses is long enough to allow significant energy storage by flashlamp pumping.
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 5, pp. 115–120, September–October, 1995. 相似文献
14.
W. Ryba-Romanowski G. Dominiak-Dzik S. Golab W. A. Pisarski I. Pracka 《Journal of Applied Spectroscopy》1995,62(5):903-909
Conclusions Nonradiative energy transfer between similar and different rare-earth ions in LiNbO3 has been evidenced for the first time. The contribution of nonradiative energy transfer to the decay of the1G4 and3H4 levels of thulium and the4S3/2 and4I13/2 levels of erbium is significant for activator concentrations of the order of several thousand ppm in LiNbO3. The excitation of higher-lying levels of both activators is transferred faster in codoped crystal to the lowest luminescent
levels, from which the luminescence in the 1–2-μm spectral region occurs. This accelerated relaxation is advantageous for
broadband optical pumping since the contribution of radiative transitions competing with the3F4−3H6 laser transition of thulium is reduced. On the other hand, it appears that erbium ions will influence adversely the efficiency
of a laser-diode-pumped LiNbO3∶Er, Tm laser operating near 1.8 μm since the part of the3H4 excitation transferred to erbium ions is emitted from the long-lived4I11/2 level of Er3+. Furthermore, the4I13/2 excitation is not transferred fully to thulium ions and is lost in4I13/2−4I15/2 emission. Lithium niobate singly doped with thulium is more promising since the cross-relaxation process that transfers the
excitation from the3H4 level to the3F4 level appears to be efficient in this host.
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 5, pp. 125–133, September–October, 1995. 相似文献
15.
LiNbO3:Cr:ZnO晶体生长和光谱特性的研究 总被引:3,自引:2,他引:1
采用提拉法从近化学计量比的熔体中生长出尺寸为φ20 mm×50 mm的优质LiNbO3:Cr:ZnO(CZLN)晶体,其光学均匀度为7.59(10-5).进行了吸收和荧光光谱的测定研究.吸收谱测试表明:Cr3 离子在晶体中有2个宽且强的吸收带及1个微弱的吸收线,两宽带中心波长分别为480和660 nm,对应于4A2→4T1和4A2→4T2两个具有相同的总自旋能级之间的跃迁,在4A2→4T2吸收宽带的长波边缘处有个很小的吸收峰,其波长为727nm,对应于4A2→2E(R线)的跃迁.荧光测试表明:当激发波长为660 nm时,CZLN晶体荧光宽带和1个较弱的荧光线峰并存,宽带范围为802~988 nm,峰值波长为871 nm,对应于4T2→2E,4A2的联合能级跃迁,荧光线峰波长约为754 nm,其强度较弱,相应于2E→4A2(零声子线)能级跃迁.计算了晶场强度和Racah参数,其Dq/B=2.72,晶体属于强场介质.研究表明,CZLN晶体具备可调谐激光晶体的基本光谱要求,且有良好的物化性能,可以实现宽频带可调谐激光输出.它又具有较大的倍频系数,有望实现420 nm附近紫外的自倍频激光输出. 相似文献
16.
Ti扩散Er3+:LiNbO3沟道波导的模式分析 总被引:1,自引:0,他引:1
本文采用有效折射率方法对Ti扩散Er3+:LiNbO3沟道波导的模式特性进行了分析,分析中考虑了Er3+:LiNbO3晶体的各向异性,并与变分法分析进行了比较,二者结果相一致。 相似文献
17.
E. Cantelar M. Quintanilla P.L. Pernas G.A. Torchia G. Lifante F. Cussó 《Journal of luminescence》2008,128(5-6):988-991
Absorption and emission cross-sections are essential spectroscopic parameters that determine the performance of rare-earth solid state lasers and amplifiers. A precise characterization of such parameters is of great interest in order to proceed with the necessary optimization stage which will assure the development of photonic devices with high efficiency. In particular, in order to model Tm3+ infrared lasers under 800 nm pumping, the absorption and emission cross-sections associated with optical transitions involving the 3H4 and 3F4 manifolds are needed. In this work, the classical McCumber theory is applied to evaluate the polarized absorption and emission cross-sections of Tm3+ ions in LiNbO3. 相似文献
18.
In this work, CW laser operation of Tm3+-doped LiNbO3 channel waveguides has been modelled. The model is based on time dependent laser rate equations coupled with the laser signal and pump photon flux equations. Steady state solutions for the population densities, pump and signal powers are obtained by using finite difference discretization of the active volume. The effects of spectroscopic parameters such as concentration dependent cross-relaxation and excess waveguide loss have been analyzed. We demonstrate good agreement with experimental data previously reported in Zn-diffused LiNbO3:Tm3+ channel waveguide lasers. It is shown also that laser performance can be substantially improved by optimizing the cavity length. 相似文献
19.
Results of cooperative phenomena investigations in the impurity subsystem of lithium niobate crystals doped with Er3+ and co-doped with Yb3+ impurity ions under continuous wave and pulsed excitation at 975 nm and 1064 nm wavelengths are presented. Dependences of some spectroscopic characteristics on the intensity of laser pumping are studied. Based on the pair centers model the analysis of the cooperative luminescence behavior in LiNbO3:Yb3++Er3+ crystals is performed. 相似文献