共查询到20条相似文献,搜索用时 0 毫秒
1.
W. Królikowski 《Applied physics. B, Lasers and optics》1997,65(4-5):541-544
Received: 11 April 1997/Revised version: 22 May 1997 相似文献
2.
D.G. Papazoglou N.C. Deliolanis A.G. Apostolidis E.D. Vanidhis 《Applied physics. B, Lasers and optics》2000,71(6):841-848
We study the diffraction efficiency of volume phase gratings in Bi12GeO20, when the grating vector, lying on a (111) plane, is at an angle with respect to the crystallographic direction. An external
bias field parallel to the direction is applied during recording, thus, the recording conditions depend on the grating vector
orientation. The basic parameters determining the diffraction efficiency are the grating vector orientation, the rotatory
power and the field-induced linear birefringence (primary and secondary). Analytic expressions for the diffraction efficiency
have been obtained by taking into account all the above-mentioned parameters, provided that linearly polarized light is incident
on the crystal. In this configuration, the influence of the secondary electro-optic effect (inverse piezoelectric and photoelastic
effects) to the diffraction efficiency is actually stronger than the influence of the primary effect. Experimental results
are given.
Received: 3 January 2000 / Revised version: 6 June 2000 / Published online: 13 September 2000 相似文献
3.
We propose an experimental method for the determination of the electro-optic coefficients of photorefractive crystals. Using
anisotropic properties of the crystal and using the response of the crystal to different polarization states of the incident
light, it is possible to determine the ratio between various electro-optic coefficients by measuring the gain in a two-wave
mixing set-up. The accuracy of the measurements is estimated and the obtained electro-optic coefficients for a Ba0.77Ca0.23TiO3 crystal show good agreement with corresponding values already known from the literature.
Received: 24 January 2000 / Revised version: 23 May 2000 / Published online: 16 August 2000 相似文献
4.
3 by photorefractive forward four-wave mixing. The intensity of a signal beam is amplified by a factor up to 3000. We show
that heating of the crystal by absorption of the pump light influences the gain because of the thermo-optic effect. Thus both,
amplification and generation can be controlled by the intensities of the pump beams.
Received: 23 January 1998 相似文献
5.
A model of deep and shallow traps has been applied in order to explain the temporal development of the signal wave amplification
as well as the pump wave depletion in two-wave-mixing experiments in the crystal Ba0.23Ca0.77TiO3 (BCT). The intensities of the outgoing waves have been studied at different intensities of the incident waves during the
first 500 s before the beams have reached their stable states. On the basis of the obtained temporal dependences of the intensities,
some material parameters of the crystal have been estimated, like excitation cross sections from the deep and shallow traps
(valence levels) into the conduction band, recombination rates from the conduction band into the valence levels, absolute
and redistributed charge densities of the deep and shallow traps, and modulations of the absorption and refractive indices.
Received: 26 May 2000 / Revised version: 26 September 2000 / Published online: 21 February 2001 相似文献
6.
Exceptionally high values of photorefractive gain coefficient of up to 100 cm-1 have been observed in Fe-doped and Fe/Tb-doped crystals of photorefractive lithium niobate. It is believed that these are
the highest observed coefficients of any crystalline photorefractive medium. Accurate measurements of gain coefficient have
been possible for the first time by using a specially cut triangular crystal which allows the use of short interaction lengths
and the complete elimination of surface reflections by having the beams incident at Brewster’s angle. Experimental results
are consistent with a simple model of photorefractive beam coupling up until the onset of noise which is observed to deplete
the pump for interaction lengths longer than 1 mm.
Received: 28 September 1998 / Revised version: 8 January 1999 / Published online: 31 March 1999 相似文献
7.
P. Pogany H.J. Eichler A. Hermerschmidt Z.G. Zhang 《Applied physics. B, Lasers and optics》1999,68(5):917-921
The power of several coherent laser beams can be transferred into a single diffraction-limited signal beam by photorefractive
coupling. The efficiency of the power transfer is investigated experimentally in the case of two pump beams. Two different
geometrical arrangements, one with overlapping (simultaneous) and the other with separate (sequential) pump beams are compared
in a BaTiO3:Ce crystal, with diffusion-driven photorefraction. We measured about the same power transfer efficiency in both arrangements
for strong signal beams, but the efficiency was higher in the sequential arrangement for weak signals. A simple theoretical
model of the power transfer process based on the standard linear two-wave-mixing theory is presented and the observed stationary
beam-coupling behavior for different pump-to-signal intensity ratios is found to be in qualitative agreement with the theoretical
predictions.
Received: 10 November 1998 / Revised version: 22 December 1998 / Published online: 24 March 1999 相似文献
8.
M.Y. Goulkov T. Granzow U. Dörfler T. Woike M. Imlau R. Pankrath 《Applied physics. B, Lasers and optics》2003,76(4):407-416
We study light-induced scattering (beam-fanning) in the photorefractive crystal SBN:Ce as a function of the polar structure
of the crystal. The spatial structure of the beam-fanning is measured at different externally applied electric fields, and
an optical hysteresis is found in the scattering. It is shown that the scattering hysteresis results from a polarization hysteresis
typical for ferroelectrics in the polar phase. New information about primary scattering in SBN is obtained, and a corresponding
model of its origin is proposed. It is shown that the intensity and angular distribution of the primary scattering strongly
depend on the polar structure of the crystal and can be affected by the subsequent action of an external field and coherent
illumination.
Received: 27 August 2002 / Revised version: 19 December 2002 / Published online: 26 March 2003
RID="*"
ID="*"Corresponding author. E-mail: mirco.imlau@uni-osnabrueck.de 相似文献
9.
N.C. Deliolanis A.G. Apostolidis E.D. Vanidhis D.G. Papazoglou 《Applied physics. B, Lasers and optics》2002,75(1):67-73
We study the influence of the application of an external electric field on the grating formed in (1-10) and (111)-cut photorefractive
sillenite crystals. Optimum conditions for application of the bias field are examined, taking into account the shift of the
grating orientation for maximum diffraction efficiency along the crystal depth. The contribution of the piezoelectric effect
is considered both in the electro-optic tensor and space charge field calculations. An analysis on the diffractive properties
under these optimum conditions shows an increase of 30% in maximum diffraction efficiency in Bi12GeO20, and experimental verification for this is provided.
Received: 5 November 2001 / Revised version: 18 April 2002 / Published online: 8 August 2002 相似文献
10.
S.M. Shandarov N.I. Nazhestkina O.V. Kobozev A.A. Kamshilin 《Applied physics. B, Lasers and optics》1999,68(5):1007-1012
The space-charge-field formation in a photorefractive crystal illuminated by a one-dimensional light pattern is studied when
an alternating square-wave electric field is applied to the crystal. We derive the general nonlinear equation for the time-averaged
distribution of the space-charge field and employ the simplified versions of this equation to analyze the space-charge-field
formation in the case of a Gaussian beam and interference light pattern. The borders of the applicability of simplified equations
and analytic expressions to describe a self-action of light beams and the large modulation effects under two-beam coupling
are estimated from the numerical calculations.
Received: 18 November 1998 / Revised version: 26 January 1999 / Published online: 12 April 1999 相似文献
11.
We have demonstrated efficient amplification of near-infrared, 0.83-μm and 1.06-μm light, in a photorefractive ring resonator
using Rh:BaTiO3. The optical power oscillating inside the ring exceeded the pump power by a factor of up to 2.34. The sensitivity of a ring
resonator to nanometer changes in its length was characterised using a piezo-mirror.
Received: 30 November 2000 / Revised version: 24 January 2001 / Published online: 20 April 2001 相似文献
12.
The first observation of optical hexagons in a medium with dominating photovoltaic charge transport – in LiNbO3:Fe – is reported. The optimum conditions for hexagon observation are revealed and discussed. The dynamics of hexagon formation
are also studied.
Received: 9 February 2000 / Published online: 8 March 2000 相似文献
13.
Molecular orientations and photorefractive effects of C60-doped nematic liquid crystals were investigated with layer-structured liquid crystal cells where a nematic phase was injected.
Regardless of the surface treatments of the layers, liquid crystals injected with nematic phase showed a higher degree of
director orientation and photorefractivity than those injected with an isotropic phase. The nematic alignment of liquid crystals
in an untreated cell is generated by a capillary flow of liquid crystal during the nematic injection. However, it was observed
that the grating formation was delayed a little longer with injection of nematic phase than with injection of isotropic phase.
Received: 11 March 2002 / Revised version: 22 April 2002 / Published online: 12 July 2002 相似文献
14.
F. Wang Z. Chen Z. Huang Q. Gong Y. Chen H. Chen 《Applied physics. B, Lasers and optics》1998,67(2):207-210
-1 and an index grating amplitude of about 4.3×10-3 were obtained. Furthermore, high solubility of the dye in PVK and high stability of the photorefractive composite were also
exhibited.
Received: 7 January 1998/Revised version: 7 April 1998 相似文献
15.
We present investigations of the etalon effect in sillenite photorefractive crystals with a pulsed frequency-doubled Nd:YAG
laser and show its influence on two- and four-wave mixing. In four-wave mixing the etalon effect allows changes of the diffraction
efficiency by more than 80%. Results are supported by theoretical considerations.
Received: 15 April 1998/Revised version: 19 June 1998 相似文献
16.
The influence of an external field on photorefractive recording in Sn2P2S6 (SPS) crystals is studied. A large gain factor of more then 15 cm-1 is achieved for a grating spacing of 12 μm at λ=0.9 μm. For an applied field exceeding ±200 V/cm a switching of the beam
coupling direction is detected, exhibiting a pronounced hysteresis.
Received: 25 October 2000 / Revised version: 18 January 2001 / Published online: 21 March 2001 相似文献
17.
G.M. Gibson G.A. Turnbull M. Ebrahimzadeh M.H. Dunn H. Karlsson G. Arvidsson F. Laurell 《Applied physics. B, Lasers and optics》1998,67(5):675-677
4 (PPKTP). We generated 12 μW of radiation tunable around 1.6 μm by difference-frequency mixing of the outputs of a frequency-doubled
Nd:YLF laser at 523 nm (240 mW) and a tunable Ti:sapphire laser near 760 nm (340 mW). A temperature tuning rate of 0.73 nm/°C
for the generated wavelength and a FWHM temperature acceptance bandwidth of 6.9 °C cm was observed. The effective d33 coefficient was estimated to be ∼5 pm/V.
Received: 02 September 1998 相似文献
18.
Transmission behavior in a photorefractive polymer film 总被引:2,自引:0,他引:2
When a p-polarized beam propagates through a high-performance photorefractive polymer composite, poly dimethyl-4-(4′-nitrophenylazo)benzene, its transmission behavior is influenced by three effects: the electroabsorption, the photorefractive
coupling with the reflected beam from the rear surface, and the amplified scattering. From the measurements on the incidence
angle dependence as well as the applied-electric-field dependence of the three effects, some conclusions are obtained. At
a small incidence angle with a low applied electric field, both the amplified scattering and the electroabsorption are small
whereas the coupling between the incident beam and the reflected beam plays a principal role. At a large incidence angle or
with a high poling electric field, the transmission is influenced mainly by the amplified scattering and the electroabsorption.
A poling electric field asymmetric loss to the amplification scattering is also observed.
Received: 18 November 1998 / Revised version: 10 February 1999 / Published online: 12 April 1999 相似文献
19.
M. Weber G. von Bally A. Shumelyuk S. Odoulov 《Applied physics. B, Lasers and optics》2002,74(1):29-33
Reflection photorefractive gratings recorded by nearly counterpropagating light waves in the near infrared are studied in
tin hypothiodiphosphate. The ratios are established for certain electrooptic tensor components responsible for reflection
grating recording, and the Debye screening length is evaluated. Reflection holograms of binary objects are recorded.
Received: 26 June 2001 / Revised version: 3 September 2001 / Published online: 29 November 2001 相似文献
20.
Generation of 840 mW of red light by frequency doubling a diode-pumped 1342 nm Nd:YVO4 laser with periodically-poled LiTaO3 总被引:1,自引:0,他引:1
J.L. He G.Z. Luo H.T. Wang S.N. Zhu Y.Y. Zhu Y.B. Chen N.B. Ming 《Applied physics. B, Lasers and optics》2002,74(6):537-539
We report an efficient generation of red light in a periodically-poled LiTaO3 (PPLT) crystal by extracavity single-pass frequency doubling of a diode-pumped, Q-switched Nd:YVO4 laser at 1342 nm. The sample used in the experiment is 20 mm in length and 14.77 μm in period. An average power of 840 mW
of the 671 nm red light is obtained with a 808 nm pump of 12.3 W, the overall optical-to-optical efficiency being 6.8%. The
measured effective nonlinear coefficient of the sample is ∼3.8 pm/V. The high conversion efficiency and output power demonstrate
that the periodically-poled crystal serving as a frequency conversion device may be used in practice to construct an all-solid-state
red laser based on an extracavity single-pass quasi-continuous scheme.
Received: 17 September 2001 / Revised version: 23 January 2002 / Published online: 8 May 2002 相似文献