共查询到20条相似文献,搜索用时 15 毫秒
1.
We investigate the effect of beam coherence on four-wave mixing via reflection gratings in photorefractive media. For the
case of phase conjugation, the results of our theoretical analysis indicate that partial coherence always leads to a drop
of signal gain and phase conjugate reflectivity in non-depleted cases. In general, the mutual coherence of the signal beam
and the pump beam can be enhanced due to the process of wave mixing. The mutual coherence of the phase conjugate beam and
one of the pump beams depends on the beam intensity ratio as well as the optical path difference. This is distinctly different
from the four-wave mixing case with a transmission grating.
Received: 15 October 1999 / Revised version: 26 June 2000 / Published online: 7 February 2001 相似文献
2.
Narrow bandwidth operation of high-power broad-area diode laser using cascaded phase-conjugate injection locking 总被引:1,自引:0,他引:1
H. Horiuchi T. Shimura T. Omatsu O. Matoba K. Kuroda 《Applied physics. B, Lasers and optics》1999,68(5):1021-1025
A broad-area laser is injection-locked by another broad-area laser that is also injection-locked by a single-mode diode laser.
Two double-phase conjugate mirrors of photorefractive BaTaO3 are used to couple the master laser beams to the first slave laser, and the first slave laser output to the second slave
laser. One of the double-phase conjugate mirrors is built up with the beams from two broad-area lasers. Two slave lasers are
oscillating in single longitudinal mode at 808.5 nm and the spectral width is the same as that of the master laser. Final
single-mode output power from the second slave broad-area laser is 840 mW, which is limited by the power of the injection
beam. This work verifies the possibility of the multi-stage cascaded injection locking of high-power diode lasers with phase-conjugate
injection.
Received: 18 November 1998 / Revised version: 29 January 1999 / Published online: 7 April 1999 相似文献
3.
R. Kowarschik L. Wenke T. Baade M. Esselbach A. Kiessling G. Notni K. Uhlendorf 《Applied physics. B, Lasers and optics》1999,69(5-6):435-443
Phase-conjugate mirrors on the basis of photorefractive crystals offer interesting possibilities of application for optical
measurement systems. In this paper we report on the application of phase-conjugate mirrors (PCMs) for optical measurement
techniques. We show different schemes for realizing PCMs and discuss characteristics such as reflectivity, fidelity, and time
behavior.
We demonstrate that two-beam interferometers with PCMs and with a suitable phase-shifting unit in the reference arm have general
advantages compared with conventional systems. It is shown that self-pumped PCMs (SPPCMs) could also be successfully used
for novelty filtering systems comparing a present state of a signal phase with a reference phase. It is found that SPPCMs
can improve both the axial and the lateral resolution of a confocal microscope. A 30% better resolution of the PCM system
is established.
Received: 14 June 1999 / Revised version: 4 October 1999 / Published online: 3 November 1999 相似文献
4.
New experimental results about a reflection-type double-pass confocal microscope with a phase-conjugate mirror are presented.
Exploiting the change of polarization of the light, when it is reflected at the object, gives the possibility to enhance the
axial resolution of the microscope compared to that of the conventional confocal microscope by a factor of 65%. Furthermore,
investigations on the time behavior of the PCM are presented.
Received: 11 January 1999 / Revised version: 25 January 1999 / Published online: 7 April 1999 相似文献
5.
T. Schneider D. Wolfframm R. Mitzner J. Reif 《Applied physics. B, Lasers and optics》1999,68(4):749-751
Received: 13 January 1999 相似文献
6.
M. Goul’kov O. Shinkarenko S. Odoulov E. Krätzig R. Pankrath 《Applied physics. B, Lasers and optics》2001,72(2):187-190
The threshold behavior is studied for a ring-loop coherent oscillator with a photorefractive strontium barium niobate (SBN)
sample. A soft onset of oscillation is revealed and critical slowing down is observed in the temporal development of light-induced
scattering below the threshold, thus pointing to a similarity with a second-order phase transition.
Received: 10 July 2000 / Published online: 20 September 2000 相似文献
7.
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
8.
We present the numerical results of the photorefractive two-wave mixing in the presence of an incoherent beam by considering
the influence of the ratios of the intensities and the light-excitation cross sections of the incoherent beam to the coherent
beams on the space-charge field and the effective coupling coefficient. The results show that the incoherent beam can control
the intensity of the coherent beams effectively. The experimental results agree with the theory well. One application is demonstrated
to obtain the positive and negative coherent replicas of an incoherent image. The coherent images have a resolution of 80.6 line
pairs/mm.
Received: 2 March 1999 / Revised version: 26 July 1999 / Published online: 20 October 1999 相似文献
9.
D.Z. Anderson V. Damiao D. Popovic Z. Popovic S. Romisch A. Sullivan 《Applied physics. B, Lasers and optics》2001,72(6):743-748
Suppression of an optical carrier from an RF modulated laser beam of wavelength 532 nm is performed using two-beam coupling
in photorefractive barium titanate. A theoretical analysis reveals that perfect suppression can be achieved at a specific
modulation strength, which depends on the gain and intensity ratio between the two beams. The experiments achieve a maximum
of -72.9±2.4 dB carrier suppression at the theoretically ideal modulation strength, and -61.0±2.4 dB for small modulation
strengths.
Received: 29 November 2000 / Revised version: 2 February 2001 / Published online: 27 April 2001 相似文献
10.
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
11.
In this paper we present an analysis of the three-valence model of photorefraction. The basic equations of the model are studied
and solved to find zero- and first-order solutions in the steady state, including expressions for the space-charge field and
the effective trap density. The intensity dependence of the solutions for the population densities and space-charge field
are analysed and discussed for varying proportions of the different valence states in the material, and the influence of some
important material parameters considered. The possible applications of these results to the experimental characterisation
of three-valence-state materials are discussed and some comparisons are made between the three-valence and the two-independent-centre
models of photorefraction.
Received: 17 November 1998 / Revised version: 8 January 1999 / Published online: 31 March 1999 相似文献
12.
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
13.
P. Zhang S. Liu C. Lou Y. Gao J. Zhao J. Xu Z. Chen 《Applied physics. B, Lasers and optics》2009,95(3):559-563
We theoretically and experimentally demonstrate that a nonconventionally biased photorefractive crystal can support hybrid
nonlinearity, i.e., coexistence of self-focusing and self-defocusing nonlinearities under an identical bias condition. It
is revealed that the nonlinearity experienced by a one-dimensional (stripe) beam can be switched between self-focusing and
self-defocusing solely by changing the beam orientation. For a two-dimensional beam, the hybrid nonlinearity leads to unusual
nonlinear beam dynamics with enhanced anisotropy and nonlocality. 相似文献
14.
P. Jullien F. Bezançon P. Mathey S. Odoulov 《Applied physics. B, Lasers and optics》2000,71(2):197-201
The strength of the transient parametric scattering in BaTiO3 is shown to be strongly dependent on the initial conditions of the sample illumination. It is shown that the effect can be
explained by a considerable increase of the seeding radiation intensity after pre-exposure of the sample to the ordinarily
polarized pump beam.
Received: 27 March 2000 / Published online: 16 June 2000 相似文献
15.
Jinhai Si Yougui Wang Qiguang Yang Peixian Ye Hongjian Tian Qingfu Zhou Huijun Xu 《Applied physics. B, Lasers and optics》1997,64(6):663-665
′ ,4′′,4′′′-tetrasulfonato-phthalocyanine/N-butyl-N′-methylanthraquinone-4,4′-bipyridinum dibromide assembly (ZnTsPc-V-AQ), was observed to be enhanced by ten times when the sample was optically pumped
by a 355 nm pump beam. The enhancement of the nonlinearity was found to be due predominantly to the charge transfer between
the two monomers of the supramolecule after optical excitation.
Received: 2 July 1996 相似文献
16.
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
17.
An incomplete correlation is discovered between the phase conjugate reflectivity in Feinberg’s Cat conjugator generating a
train of regular pulses with the cw incident pump wave and inhibited specular reflectivity from the sample. The frequency
chirp within every spike of conjugate wave is shown to affect the efficiency of the secondary phase conjugator generating
auxiliary waves in the direction of Fresnel reflection of the incident wave.
Received: 25 November 1998 / Revised version: 11 January 1999 / Published online: 31 March 1999 相似文献
18.
60 at 1.064 μm is determined by the optical Kerr effect in toluene solution. Values of -6.5×10-33 esu and 2.0×10-32 esu for the real and imaginary parts of γ, respectively, are obtained. Based on the experimental results and symmetry constraint,
it is concluded that a three-level model is not adequate to describe the third-order nonlinearity of C60. It is also inferred that the non-resonant γ of C60 should be positive in sign, which is in agreement with reported off-resonant measurements of γ of C60 by third-harmonic generation.
Received: 3 September 1997/Revised version: 1 December 1997 相似文献
19.
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
20.
Impurity levels, light-induced and thermo-induced charge transfer processes in Rh-doped and Ce-doped photorefractive BaTiO3 were studied. The thermal depths and optical transitions of these impurity levels in the crystals were determined by using
such methods as light-induced absorption, thermo-induced absorption, and grating dark decay. The origins of these impurity
levels were discussed. We demonstrated, for the first time to our knowledge, that thermo-induced absorption spectroscopy is
a useful and complementary technique for investigating the impurity levels in photorefractive crystals. With this technique,
the deep impurity level generated by Ce in BaTiO3:Ce was revealed and identified.
Received: 7 July 1999 / Revised version: 24 September 19999 / Published online: 2 February 2000 相似文献