共查询到20条相似文献,搜索用时 15 毫秒
1.
The optical properties of Yb3+ ions in LiTaO3:Nd,Yb crystals 总被引:1,自引:0,他引:1
I. Sokólska W. Ryba-Romanowski S. Gołab T. Lukasiewicz 《Applied physics. B, Lasers and optics》1997,65(4-5):495-498
3+ ions excited by energy transfer from Nd3+ ions in LiTaO3:Nd, Yb crystals are presented. The emission band of Yb3+ ions is broad, due to the strong phonon-coupling and to the relative large Stark-splitting of the ground 2F7/2 multiplet. The emission cross-section was evaluated by the reciprocity method, and a value of 0.53×10-20 cm2 was obtained. The gain coefficients derived for the inversion parameters in the range 0.05 to 0.5 indicate positive gain
in the 985–1070 nm range.
Received: 17 March 1997/Revised version: 10 June 1997 相似文献
2.
Dynamics of the Yb3+ to Er3+ energy transfer in LiNbO3 总被引:1,自引:0,他引:1
The energy transfer dynamics between Yb3+ and Er3+ ions in lithium niobate is investigated after ytterbium-pulsed excitation at 920 nm. The sensitisation of the LiNbO3:Er3+ system with Yb3+ ions does not modify the lifetime of the 4I13/2 erbium level (1.5-μm emission), whereas it induces a marked, concentration-dependent change in the lifetime of the 2F5/2 (Yb3+) and 4S3/2 (Er3+) multiplets (1060-nm and 550-nm emissions, respectively). The results are analysed by using the rate-equation formalism and
cross-relaxation model for the energy transfer.
Received: 15 October 1998 / Revised version: 24 November 1998 / Published online: 24 February 1999 相似文献
3.
The complete set of self-consistent parameters of nominally undoped LiNbO3 crystals of congruent composition that describe the electro-optic, piezoelectric, elasto-optic, elastic, and dielectric response
has been determined by numerically evaluating available measurements. The parameters were determined at room temperature and
consist of the low-frequency clamped dielectric constants εS
ij, elastic stiffness constants at constant electric field CE
ijkl, piezoelectric stress coefficients eijk, elasto-optic constants at constant electric field pE
ijkl, and clamped electro-optic coefficients rS
ijk. It is shown that the complete set is required for calculating the effective electro-optic coefficients and dielectric constants
in photorefractive applications of LiNbO3.
Received: 4 January 2002 / Revised version: 1 February 2002 / Published online: 14 March 2002 相似文献
4.
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
5.
G.K. Kitaeva I.I. Naumova A.A. Mikhailovsky P.S. Losevsky A.N. Penin 《Applied physics. B, Lasers and optics》1998,66(2):201-205
3 crystals are measured in the transparency region (with the accuracy ±0.0002) and for the upper phonon polariton branch (with
the accuracy ±0.003–±0.05), from 0.44 μm up to 10.5 μm. The method of spontaneous parametric light scattering is used for
measurement of the ordinary refractive index dispersion in the mid-infrared region and for determination of the domain grating
period d=5.6±0.2 μm in the periodically-poled crystal.
Received: 29 January 1997/Revised version: 10 July 1997 相似文献
6.
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
7.
Crystalline structure and optical spectroscopy of Er3+-doped KGd(WO4)2 single crystals 总被引:2,自引:0,他引:2
M.C. Pujol M. Rico C. Zaldo R. Solé V. Nikolov X. Solans M. Aguiló F. Díaz 《Applied physics. B, Lasers and optics》1999,68(2):187-197
4 )2 single crystals doped with Er3+ have been grown by the flux top-seeded-solution growth method. The crystallographic structure of the lattice has been refined,
being the lattice constants a=10.652(4), b=10.374(6), c=7.582(2) Å, β=130.80(2)°. The refractive index dispersion of the host
has been measured in the 350–1500 nm range. The optical absorption and photoluminescence properties of Er3+ have been characterised in the 5–300 K temperature range. At 5 K, the absorption and emission bands show the (2J+1)/2 multiplet
splittings expected for the C2 symmetry site of Er in the Gd site. The energy positions and halfwidths of the 72 sublevels observed have been tabulated
as well as the cross sections of the different multiplets. Six emission band sets have been observed under excitation of the
4F7/2 multiplet. The Judd–Ofelt (JO) parameters of Er3+ in KGW have been calculated: Ω2=8.90×10-20 cm2, Ω4=0.96×10-20 cm2, Ω6=0.82×10-20 cm2. Lifetimes of the 4S3/2, 4F9/2, and 4I11/2 multiplets have been measured in the 5–300 K range of temperature and compared with those calculated from the JO theory.
A reduction of the 4S3/2 and 4I11/2 measured lifetimes with increasing erbium concentration has been observed, moreover the presence of multiphonon non-radiative
processes is inferred from the temperature dependence of the lifetimes.
Received: 15 December 1997/Revised version: 10 July 1998 相似文献
8.
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
9.
X-ray powder diffraction (XRD) of MgPc indicated that the material in the powder form is polycrystalline with monoclinic structure. Miller indices, h k l, values for each diffraction peak in XRD spectrum were calculated. Thermal evaporation technique was used to deposit MgPc thin films. The XRD studies were carried out for MgPc thin films where the results confirm the amorphous nature for the as-deposited films. While, polycrystalline films orientated preferentially to (1 0 0) plane with an amorphous background were obtained for films annealed at 623 K for 3 h. Optical properties of MgPc thin films were characterised by using spectrophotometric measurements of transmittance and reflectance in the spectral range from 190 to 2500 nm. The refractive index, n, and the absorption index, k, were calculated. According to the analysis of dispersion curves, the parameters, namely; the optical absorption coefficient (α), molar extinction coefficient (?molar), oscillator energy (Eos), oscillator strength (f), and electric dipole strength (q2) were also evaluated. The recorded absorption measurements in the UV-vis region show two well defined absorption bands of phthalocyanine molecule; namely the Q-band and the Soret (B-band). The Q-band showed its splitting characteristic (Davydov splitting), and ΔQ was obtained as 0.15 eV. The analysis of the spectral behaviour of the absorption coefficient (α), in the absorption region revealed indirect transitions. The transport and the near onset energy gaps were estimated as respectively 2.74 ± 0.02 and 1.34 ± 0.01 eV. 相似文献
10.
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
11.
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
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.
C.J. da Silva M.T. de Araujo E.A. Gouveia A.S. Gouveia-Neto 《Applied physics. B, Lasers and optics》2000,70(2):185-188
The temperature effect upon infrared-to-visible frequency upconversion fluorescence emission in Yb3+-sensitized Er3+-doped germanosilicate optical fibers excited with cw radiation at 1.064 μm is investigated. The experimental results revealed
an eightfold enhancement in the visible upconversion emission intensity as the fiber temperature was increased from 17 °C
to 180 °C. The fluorescence emission enhancement is attributed to the temperature-dependent multiphonon-assisted anti-Stokes
excitation process of the ytterbium sensitizer. A theoretical approach that takes into account a sensitizer absorption cross-section,
which depends on the phonon occupation number, has proven to agree very well with the experimental data
Received: 6 April 1999 / Revised version: 27 August 1999 / Published online: 27 January 2000 相似文献
14.
G. Dominiak-Dzik S. Gołąb I. Pracka W. Ryba-Romanowski 《Applied Physics A: Materials Science & Processing》1994,58(6):551-555
Nonequivalent Er3+ sites in LiNbO3 crystals have been evidenced by low-temperature optical absorption measurements. The radiative transition rates for the 4
S
3/2, 4
F
9/2, 4
I
9/2, 4
I
11/2, and 4
I
13/2 levels have been evaluated by the Judd-Ofelt method, and the contribution of multiphonon relaxation to the decay of excited states has been estimated. The quantum efficiency of the 4
I
11/2 level has been estimated to be 6% only, thus the excitation of levels lower than 4
S
3/2 is expected to populate efficiently the 4
I
13/2 level. 相似文献
15.
J.F. Philipps T. Töpfer H. Ebendorff-Heidepriem D. Ehrt R. Sauerbrey 《Applied physics. B, Lasers and optics》2001,72(4):399-405
Er3+ emission and lasing properties at 1.5 μm were studied in fluoride phosphate glasses (FP20) with different doping concentrations
as well as in a commercial phosphate glass (Kigre QX). Emission decay behaviour at 1 μm and 1.5 μm was examined with respect
to energy transfer between ytterbium and erbium. Emission cross-sections were determined using the reciprocity and Füchtbauer–Ladenburg
methods. Gain spectra were calculated for the glasses and related to differences in the tuning curves and lasing properties.
The temperature rise due to the quantum defect was determined via the ratios of green upconversion luminescence for different
pump powers. The results from the laser and tuning experiments indicate that the FP20 glass offers good possibilities in broadband
amplification and the generation of ultrashort pulses.
Received: 24 August 2000 / Revised version: 27 October 2000 / Published online: 7 February 2001 相似文献
16.
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
17.
In this paper, we report the near-infrared luminescence from the Er3+/Yb3+, Tm3+/Yb3+, Er3+/Tm3+ and Nd3+ ions-doped TeO2-ZnO-B2O3-Li2O-Na2O glasses for optical amplification. The X-ray diffraction (XRD) and differential scanning calorimetry (DSC) profiles of the host glass matrix have been carried out. From the DSC thermogram, glass transition (Tg), crystallization (Tc) and melting (Tm) temperatures have been evaluated. The near-infrared spectra of Er3+/Yb3+, Tm3+/Yb3+, Er3+/Tm3+ and Nd3+ ions-doped glasses have shown full-width at half-maxima (FWHM) around 58, 127, 87 and 35 nm, respectively. These glasses with better thermal stability and broad near-infrared emissions should have potential applications in broadly tunable laser sources and broadband optical amplification at low-loss telecommunication windows. 相似文献
18.
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
19.
Spectroscopic characterization of a Tm3+:SrGdGa3O7 crystal 总被引:2,自引:0,他引:2
W. Ryba-Romanowski S. Gołvab I. Sokólska G. Dominiak-Dzik J. Zawadzka M. Berkowski J. Fink-Finowicki M. Baba 《Applied physics. B, Lasers and optics》1999,68(2):199-205
3 O7 crystal have been recorded at room temperature and at approximately 8 K. Room-temperature luminescence lifetimes of 1D2, 1G4, 3H4, and 3F4 states have been measured for Tm concentration ranging from [%at.]0.5 to [%at.]9. Based upon these data the crystal field
splitting of luminescent states has been derived and radiative transitions rates have been evaluated. Strong self-quenching
of luminescence originating in the 1G4 and 3H4 states has been found in this activator–host combination. Peak emission cross section of the potential laser transition at
1800 nm was determined to be 3.9×10-21 cm2 and the gain coefficient versus wavelength was estimated and discussed.
Received: 14 April 1998/Revised version: 10 August 1998 相似文献
20.
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