共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
S. Balasubramanian I. Lahiri Y. Ding M.R. Melloch D.D. Nolte 《Applied physics. B, Lasers and optics》1999,68(5):863-869
The photorefractive response to an applied electric field is measured in a photorefractive quantum well, providing evidence
in favor of the nonlinear transport in the device due to the hot electrons. The reduced mobility of the hot electrons limits
the drift length, and thereby limits fringe overshoot. Thus the nonlinear transport prevents the slowing down of the grating
writing rate for increasing fields which is common in bulk photorefractives. The photorefractive phase shift in transverse-field
photorefractive quantum wells is measured as a function of the frequency offset between two laser writing beams that generate
moving gratings. The two-wave mixing passes through a maximum at an optimum frequency which depends on the magnitude and the
sign of the applied dc electric field. The phase shift associated with the moving grating adds or subtracts from the static
phase shift induced by hot-electron transport in the semiconductor quantum wells, depending on the sign of the field and the
sign of the dominant photocarriers. We observe a linear relationship between the roll-off frequency and the power of the writing
beams.
Received: 26 November 1998 / Revised version: 22 January 1999 / Published online: 12 April 1999 相似文献
3.
This paper presents experimental evidence that orthogonally crossed dark soliton stripes form quasi-two-dimensional spatial
solitons with a soliton constant equal to that of singly charged optical vortices. Besides the pairs of oppositely charged
optical vortex solitons, the snake instability of the dark formation at moderate saturation is found to lead to generation
of steering mixed edge–screw phase dislocations with zero total topological charges.
Received: 26 October 1998 / Revised version: 19 January 1999 / Published online: 12 May 1999 相似文献
4.
A. Dreischuh G.G. Paulus F. Zacher I. Velchev 《Applied physics. B, Lasers and optics》1999,69(2):113-117
This paper presents arguments for the existence and dynamics of one-dimensional odd dark beams of finite length in bulk Kerr
nonlinear media. Their characteristic mixed edge–screw phase dislocations force them to steer in space. The modulational stability
of these dark beams and one possible interaction scheme are discussed.
Received: 26 October 1998 / Revised version: 19 January 1999 / Published online: 12 May 1999 相似文献
5.
K.T. Stoychev M.T. Primatarowa K. Marinov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):301-304
Effects of the exciton and polariton dispersions and the nonlinear exciton and photon interactions on the properties of polariton
solitons in molecular crystals are investigated. Higher-order terms and phase-modulation (chirp) are taken into account. Bright-
and dark-soliton solutions of the resulting modified nonlinear Schr?dinger (NLS) equation are presented. Nonlinearity- and
dispersion-induced critical points on the polariton dispersion curve are obtained, separating regions with different solutions.
Received 2 October 2001 / Received in final form 23 May 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: Stoychev@issp.bas.bg 相似文献
6.
E. Ahouzi C. Iemmi S. Ledesma V. Lashin K. Chalasinska-Macukov J. Campos M. J. Yzuel 《Applied physics. B, Lasers and optics》1997,64(3):331-338
We study an experimental setup to perform pattern recognition by correlation methods. This setup implements the Pure Phase
Correlation (PPC) method, let us say, it only takes into account the phase distributions of the Fourier transform of the scene
and the target. An experimental study of a PPC method is presented. A phase measurement interferometric technique is used
to extract the phase of the Fourier transform of the correlation function. Some aspects related to the intermodulation are
examined. Experimental PPC with improved discrimination capability obtained with binary masks is also considered. The experiments
are carried out with segmented scenes and with multiobject scenes.
Received: 22 March 1996/Revised version: 17 July 1996 相似文献
7.
In this paper, we derived the Z-scan formula for a photorefractive crystal sample under an external applied electric field.
The far-field diffraction pattern of a Gaussian beam wavefront through a photorefractive crystal is calculated by considering
spatial-phase perturbation induced by the space-charge field. The photorefractive drift nonlinearities and correspondingly,
the electro-optic coefficients r
33, r
13, (r
23) and the characteristic ratio n
3
e
r
33/n
3
o
r
13 for a cerium-doped Sr0.61Ba0.39Nb2O6 crystal are determined from the Z-scan experiments. Z-scan with enhanced sensitivity is also realized by measuring the normalized
transmittance at the off-axis position in the far field. A deviation between the off-axis Z-scan experimental results and
the theoretical prediction is discussed too.
Received: 22 July 1996/Revised version: 7 October 1996 相似文献
8.
H.C. Pedersen P.M. Johansen D.J. Webb E.V. Podivilov 《Applied physics. B, Lasers and optics》1999,68(5):967-970
By using an alternative setup for photorefractive parametric oscillation in which wave mixing between the recording beams
is avoided it has become possible to make more detailed comparisons with the space-charge wave theory. In the present paper
we compare the experimental features of longitudinal parametric oscillation observed in a crystal of Bi12SiO20 with the theoretical predictions.
Received: 24 November 1998 / Revised version: 13 January 1999 / Published online: 7 April 1999 相似文献
9.
D. Neshev A. Dreischuh G.G. Paulus H. Walther 《Applied physics. B, Lasers and optics》2001,72(7):849-854
Numerical simulations on the evolution of step-screw and edge-screw optical phase dislocations in bulk saturable self-defocusing
nonlinear media are presented, with emphasis on their ability to induce steering waveguides for signal beams (pulses). Two
schemes for directional coupling of such signals, both ensuring a reasonable coupling-to-cross-talk efficiency ratio, are
investigated. The parameters useful for performance optimization of the couplers are discussed.
Received: 19 July 2000 / Revised version: 5 February 2001 / Published online: 27 April 2001 相似文献
10.
V.V. Shepelevich Y. Hu A. Firsov E. Shamonina K.H. Ringhofer 《Applied physics. B, Lasers and optics》1999,68(5):923-929
Simple analytical expressions for the dependence of the maximum gain on the polarization angle of the interacting light waves
and the crystal thickness are obtained for two-wave mixing in a cubic optically active piezoelectric crystal. By applying
the theory to Bi12SiO20 and Bi12TiO20 crystals, the optimum gain is found also with respect to the grating orientation. The r?le of the (inverse) piezoelectric
effect is investigated.
Received: 23 November 1998 / Revised version: 8 January 1999 / Published online: 7 April 1999 相似文献
11.
We show that in crystals of symmetry 3m (lacking optical activity) two regimes are possible for two-wave mixing in the longitudinal geometry: one regime is similar
to ordinary two-wave mixing where energy exchange is always in the same direction whereas the other one is oscillatory with
energy transfer in both directions.
Received: 27 November 1998 / Revised version: 18 February 1999 / Published online: 12 April 1999 相似文献
12.
A. Apolonskii S. Baluschev U. Hinze E. Tiemann B. Wellegehausen 《Applied physics. B, Lasers and optics》1997,64(4):435-442
In a double-Λ level configuration of Na2 molecules, involving rotational–vibrational levels of the X, A and B bands, continuous resonant frequency mixing ω4=ω1−ω2+ω3 is demonstrated. A DCM dye laser at 661 nm (λ1) pumps a molecular Raman laser at 746 nm (λ2) in a sodium heatpipe, which is used to generate the molecular vapour. In the same heatpipe, both fields are mixed with the
radiation of an argon-ion laser at 514 nm (λ3) to generate up-converted laser radiation at 473 nm (λ4). For laser powers of 200 mW (λ1), 700 mW (λ2, internal power) and 140 mW (λ3), an output power of 120 μW (λ4) has been achieved. Dependences of the generated radiation on the pump fields (powers and detunings) and polarization features
are presented; influences of coherent coupling and population transfer mechanisms are discussed.
Received: 7 October 1996 相似文献
13.
R.V. Litvinov 《Applied physics. B, Lasers and optics》2002,75(8):853-860
The steady-state two-wave interaction in a cubic crystal of the symmetry group 3m with the non-local photorefractive response in the absence of an external electric field is considered for the case of arbitrary
interaction orientation with respect to the crystallographic coordinate system and for arbitrary intensities and polarization
states of incident light waves. The self-diffraction problem is described on the basis of four coupled-wave equations in terms
of the complex scalar amplitudes of components of the light waves with orthogonal linear polarization. The derived conservation
laws are valid for the non-linear dependency of the photorefractive-grating amplitude on the modulation coefficient of the
interference light pattern. It follows from these laws that the two non-unidirectional energy fluxes can form the total energy
exchange between the two interacting light waves. A set of independent conservation laws allows us to decouple the coupled-wave
equations and to obtain their analytical solution, at least, in the form of quadrature formulae. For example, such a solution
is derived for the case of linearly polarized incident light waves and for the linearized dependency of the photorefractive-grating
amplitude on the modulation coefficient. The explicit analytical expressions for the scalar amplitudes are obtained for the
transversal electro-optic configuration of interaction. The possibility of polarization-state transformation of light waves
without energy exchange between them is shown.
Received: 30 July 2002 / Published online: 11 December 2002
RID="*"
ID="*"Corresponding author. Fax: +7-3822/414321, E-mail: litvinov@ed.rk.tusur.ru 相似文献
14.
Steady-state and time-resolved off-Bragg-angle diffraction experiments are used to determine the structure and the dynamics
of photorefractive gratings induced by interband photoexcitation. In potassium niobate, we identify in such gratings basically
a two-layer structure. Close to the surface, we find a space-charge electric field generated by a charge modulation stored
directly in the bands. This grating component is typically 50 μm thick, the amplitude of the refractive index modulation is
larger than 10-4, and the response time is a few μs for resonant intensities of 100 mW cm-2. This component is also robust under non-resonant illumination. Deeper in the crystal, a second holographic layer extends
over a few hundreds of μm, its amplitude is smaller, and its slower response time is in the ms range. The mutual phase shift
between the grating components is also determined.
Received: 23 November 1998 / Revised version: 14 January 1999 / Published online: 12 April 1999 相似文献
15.
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
16.
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
17.
We develop a phenomenological model of the double-phase-conjugate mirror grating formation based on geometrical considerations.
We show that the grating develops from one lateral side of the interaction zone towards the other side. This model is confirmed
by the behaviour of different configurations of a 2-zone double-phase-conjugate mirror. Finally, we obtained stable operation
in InP:Fe, this made it possible to implement a 1×8 switch between single-mode fibres at telecom wavelength with 12% global
efficiency and 200 ms reconfiguration time.
Received: 6 November 1998 / Revised version: 18 February 1999 / Published online: 7 April 1999 相似文献
18.
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
19.
V. G. Ostroumov F. Heine S. Kück G. Huber V. A. Mikhailov I. A. Shcherbakov 《Applied physics. B, Lasers and optics》1997,64(3):301-305
An intracavity frequency-doubled 10%Nd : LaSc3(BO3)4 (Nd : LSB) laser was investigated in different resonator configurations and in different operation modes under continuous
wave (cw) and quasi-cw laser-diode pumping. With a Cr4+ : YAG passive modulator and a KTP crystal the second-harmonic output power at 531 nm amounted to 190 mW in Q-switched TEM00 mode at 750 mW of pump power. In a sandwich resonator, when all the optical elements were in direct contact with each other,
0.8 W of green output power was obtained in cw mode under 2.7 W of pump power with a slope efficiency of 44%. In the same
setup under fiber-coupled diode-laser array pumping (5.6 W of incident power), 1.2 W of green output power was achieved in
cw mode and 1.4 W in quasi-cw mode.
Received: 30 April 1996/Revised version: 1 July 1996 相似文献
20.
M. Weber F. Rickermann F. Abbing G. von Bally 《Applied physics. B, Lasers and optics》1999,68(5):1069-1072
A holographic double-exposure interferometer for quasi real-time analysis is realized, utilizing a photorefractive BTO:Cd
crystal for hologram recording. Heating of the crystal reduces the time required to reach the steady-state working situation.
Light-induced absorption losses are reduced by heating as well. Additionally, the diffraction efficiency is increased by this
method. A sixfold increase in the light intensity of the reconstructed interferogram is achieved.
Received: 2 December 1998 / Revised version: 28 January 1999 / Published online: 7 April 1999 相似文献