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1.
X-Ray-induced absorption changes in Cu-doped lithium niobate crystals (LiNbO3) are investigated. All induced photochromic effects are fully reversible, i.e., illumination with white light annihilates
the absorption changes. With increasing doping level, a decrease in the saturation value of the absorption changes is found.
Changes of the Li concentration of the crystal to a more stoichiometric composition via Li indiffusion further decreases the
photochromic effect. For sufficient X-ray doses, the saturation value is independent of the radiation energy in the measured
range from 50–150 kV. The spectral distribution of the X-ray-induced absorption changes and the slow dark decay indicate that
the additional absorption results from an increase of the Cu+ concentration.
Received: 20 December 2000 / Revised version: 24 January 2001 / Published online: 27 April 2001 相似文献
2.
The impact of protons and copper on the dark conductivity of copper-doped photorefractive lithium niobate crystals is investigated
by observation of the dark decay of holograms. The dark conductivity is significantly smaller than that of iron-doped lithium
niobate. A non-mono-exponential hologram decay is observed, which needs to be considered for multiplexing of holograms.
Received: 25 March 2002 / Published online: 2 May 2002 相似文献
3.
M. Luennemann U. Hartwig G. Panotopoulos K. Buse 《Applied physics. B, Lasers and optics》2003,76(4):403-406
The electrooptic effect in lithium niobate crystals (LiNbO3) for extremely high externally applied electric fields of up to 65 kV/mm is investigated. Homogeneous electrooptic refractive-index
changes of up to 4.8×10-3 are found for ordinarily polarized light. No quadratic electrooptic effect is observed. An upper bound for the quadratic
electrooptic coefficient of |s13|≤2.3×10-21 m2/V2 is determined. Electrooptic, angular, and wavelength tuning of the Bragg condition of a thermally fixed hologram are demonstrated.
Received: 29 October 2002 / Revised version: 14 January 2003 / Published online: 26 March 2003
RID="*"
ID="*"Corresponding author. E-mail: ml@uni-bonn.de 相似文献
4.
M. H. Abdallah Y. Ramaden S. A. Jawad M. Hassan M. S. Ahmad A. M. Zihlif 《Applied Physics A: Materials Science & Processing》1995,60(5):437-440
The effect of annealing on the electrical properties and the refractive index of red mercuric iodide (HgI2) single crystals is investigated. The ac-impedance and phase angle were measured in the frequency range from 100 Hz to 10 kHz at different annealing temperatures. The ac-conductivity, dielectric constants, loss tangent and the refractive index as a function of frequency are determined. The results are discussed in terms of structural changes taking place as a result of the heat treatment of the HgI2 single crystals. 相似文献
5.
Photorefractive properties of highly-doped lithium niobate crystals in the visible and near-infrared 总被引:5,自引:0,他引:5
Light-induced refractive-index changes, bulk-photovoltaic current densities, and photoconductivities of photorefractive iron-doped
lithium niobate crystals (iron concentrations between 0.02 and 0.17 wt. %) are investigated in detail using visible and near-infrared
light. It turns out that the one-center model predicts the material performance correctly for small iron concentrations (cFe<0.06 wt. % Fe2O3), only. A strong increase of the photoconductivity for higher doping levels limits the space-charge fields. Refractive-index
changes up to 7×10-4 for green and 2.8×10-4 for near-infrared ordinarily polarized light are obtained. The corresponding hologram multiplexing numbers are 11 for green
and 5 for near-infrared light.
Received: 18 November 1998 / Revised version: 8 January 1999 / Published online: 7 April 1999 相似文献
6.
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
7.
Poling dynamics of lithium niobate crystals 总被引:2,自引:0,他引:2
Ferroelectric domain reversal via electric field poling of congruently melting lithium niobate (LiNbO3) crystals is investigated. An electro-optic interferometric observation technique reveals spatial and temporal dynamics of
the poling process. Starting from seeds, the domains grow until the entire crystal has a switched polarization. During the
switching process the boundaries are preferentially aligned along the crystallographic axes. The coercive field between two
sequenced domain inversions is transiently reduced after a poling event, and recovers exponentially with a time constant of
about half a minute. No light-induced change of the recovery time constant, neither with green nor with ultraviolet light,
is observed. The results are of relevance for domain engineering of LiNbO3 crystals.
Received: 6 February 2003 / Published online: 9 April 2003
RID="*"
ID="*"Corresponding author. Fax: +49-228/734038, E-mail: wengler@physik.uni-bonn.de 相似文献
8.
M. R. R. Gesualdi C. Jacinto T. Catunda M. Muramatsu V. Pilla 《Applied physics. B, Lasers and optics》2008,93(4):879-883
In this work, the light-induced lens effect due to thermal and/or photorefractive processes was studied in pyroelectric (undoped
and Fe2+-doped) lithium niobate crystals (LiNbO3) using thermal lens spectrometry with a two-beam (pump–probe) mode-mismatched configuration. The measurements were carried
out at two pump beam wavelengths (514.5 and 750 nm) to establish a full understanding of the present effects in this material
(thermal and/or photorefractive). We present an easy-to-implement method to determine quantitative values of the pyroelectric
coefficient (dP
s/dT), its contribution to the thermal effect and other thermo-optical parameters like thermal diffusivity (D), thermal conductivity (K) and temperature coefficient of the optical path length change (ds/dT). These measurements were performed in LiNbO3 and LiNbO3:Fe (0.1 ppm Fe2+) crystals with c axis along the direction of laser propagation. 相似文献
9.
M. Abarkan M. Aillerie J. P. Salvestrini M. D. Fontana E. P. Kokanyan 《Applied physics. B, Lasers and optics》2008,92(4):603-608
We report the optical and dielectric properties in hafnium (Hf)-doped lithium niobate (LN) crystals. We investigated samples
of congruent composition with various doping concentration varying from 0 to 8 mol%. The clamped and unclamped values of the
electro-optic coefficient r
22 of Hf-doped LN and the corresponding dielectric permittivity as well, have been experimentally determined and compared with
the results obtained in undoped congruent LN crystals. We show that the electro-optic and dielectric properties are only slightly
affected by the introduction of hafnium ions, and therefore Hf-doped LN has the advantage of low photorefractive damage compared
with the undoped congruent LN. 相似文献
10.
A new approach to the intrinsic and extrinsic defect subsystems, considering them as one integrated functional system, is
developed for complex oxides. The strong interrelation of these subsystems becomes especially apparent when concentrations
of both defect classes are comparable. A new parameter, reflecting the total intrinsic defect concentration, is introduced
to determine the degree of crystal imperfection. The necessity of at least two calibrated samples – congruent and regularly
ordered crystals – is substantiated. The accuracy by which the parameter can be determined can serve as a criterion in comparison
of different methods of crystal characterisation. A procedure for crystal calibration by several physical characteristics
is illustrated. Such a heuristic generalisation of the concept of mutual correlation of the whole defect system and the material
only became possible on the basis of experimental and theoretical study of large numbers of LiNbO3 crystals. The spectra of EPR, NMR, ENDOR, and other properties of crystals with different compositions, diverse modifiers
(K, Mg,...), and various probe impurities have been analysed. It is found that crystals with vanishingly small concentration
of intrinsic defects offer extraordinary informative opportunities. Their micro- and macroscopic properties are discussed.
The developed ideas have a general character; therefore they should also be valid for other non-stoichiometric complex oxides.
Received: 3 December 1998 / Revised version: 15 February 1999 / Published online: 12 April 1999 相似文献
11.
T. Töpfer J. Hein J. Philipps D. Ehrt R. Sauerbrey 《Applied physics. B, Lasers and optics》2000,71(2):203-206
In this paper we report on measurements of the nonlinear refractive index n2 at 1047 nm of various fluoride-phosphate laser glasses relative to fused silica using degenerate four-wave mixing. We find
good agreement with empirical estimates obtained from the d-line linear refractive index and the Abbe number for pure fluoride-phosphate
glasses. Significant increase of n2 is observed when adding sulfate and niobium oxide to the glass composition offering tailorable nonlinear properties for glasses
employed in short pulse laser oscillators.
Received: 27 December 1999 / Published online: 24 March 2000 相似文献
12.
Influence of optical-damage-resistant dopants on the nonlinear optical properties of lithium niobate
Using the chemical-bond method, nonlinear optical properties of lithium niobate containing different dopants are calculated.
In crystals with stoichiometric composition the second order nonlinear susceptibility decreases approximately linearly with
increasing dopant concentration. Among the dopants studied – Mg, Zn and In – this behaviour is most highly expressed for In
doping. In contrast to that, congruently grown crystals show a different behaviour; only a weak dependence on the dopant concentration
is found for, for example, Mg-doped material.
Received: 24 October 2000 / Published online: 21 March 2001 相似文献
13.
P. Ganguly D. C. Sen S. Datt J. C. Biswas S. K. Lahiri 《Fiber and Integrated Optics》1996,15(2):135-147
A generally applicable method to simulate the two-dimensional profiles of Ti-concentration and refractive index of Ti:LiNbO3, waveguides is presented. The influence of the fabricational parameters on the refractive index profiles has been studied in detail. The model parameters are extracted from the available experimental data. The computed values of surface refractive index change agree closely with the experimental results. The model is also extended for coupled waveguides. 相似文献
14.
S. Loheide S. Riehemann E. Krätzig 《Applied Physics A: Materials Science & Processing》1994,58(4):343-347
Beam-coupling is investigated in a nominally pure tetragonal potassium Tantalate-Niobate (KTN) crystal as a function of external electric field, spatial frequency and light wavelength. The variation of these parameters leads to a change of the direction of energy transfer between the two recording beams. The experimental results can be consistently described by a one-center charge-transport model taking into account electron and hole contributions to photoconductivity and space-charge limitations due to the available trap density. 相似文献
15.
S. Mailis P.T. Brown C.L. Sones I. Zergioti R.W. Eason 《Applied Physics A: Materials Science & Processing》2002,74(2):135-137
Modification of the chemical etching behaviour of undoped congruent z-cut lithium niobate single crystals is achieved by pre-illumination
of the –z face of the crystal with sub-ps ultraviolet laser radiation at 248 nm, at energy fluences below the threshold for
ablation. A systematic study of the effect of the energy fluence and total exposure on the etch frustration is presented.
Received: 23 July 2001 / Accepted: 28 September 2001 / Published online: 20 December 2001 相似文献
16.
We demonstrate a new method of electrical fixing of waveguiding channels in strontium-barium niobate. The method is applicable
to both bulk material and planar SBN waveguides. Waveguiding is achieved for extraordinarily polarized light. We suggest that
the fixing is based on a partial depoling of the crystal rather than on internal electric fields.
Received: 29 January 2001 / Published online: 27 April 2001 相似文献
17.
1 L) and the relative strength (x) of PCG compared with PRG in two cases: (i) when g1L>0 and x>1 so that there exists either pure PRG or PRG dominates over PCG, and (ii) when g1L<0 and x<-1 so that there exists either pure PCG or PCG dominates over PRG. The threshold condition g1L>(g1L)Th=2x(1+1/R) with R>1 and the effective coupling strength, g2L=g1L/x>0 with 1<x<-1, need to be satisfied for the bistability. Possible regions of bistability affect the position
of the region for the intensity ratio (m) of the incident beams where two branched multiple solutions exist and hysteresis
in the gain is expected. Gain solutions are found to be single valued without bistability when g2L<0. A comparison between the mixed grating gain and pure PRG/PCG gains with the occurance of bistability is presented and
interpreted physically.
Received: 9 January 1996/Revised version: 17 September 1996 相似文献
18.
Transmittance measurements were carried out for LiF thin films directly after preparation, then one day, one week, four weeks
and six weeks later. The aging effect on the optical properties of the film was thus studied. This showed that the aged LiF
films have refractive indices larger than those of fresh films. 相似文献
19.
J.-H. Jia Y. Wang Z.-X. Chen L.-D. Zhang 《Applied Physics A: Materials Science & Processing》1997,65(4-5):383-385
Received: 5 June 1997/Accepted: 30 July 1997 相似文献
20.