共查询到20条相似文献,搜索用时 0 毫秒
1.
C. Weilnau W. Królikowski E.A. Ostrovskaya M. Ahles M. Geisser G. McCarthy C. Denz Y.S. Kivshar B. Luther-Davies 《Applied physics. B, Lasers and optics》2001,72(6):723-727
We review the generation of the recently predicted multi-component spatial optical solitons in a saturable nonlinear bulk
medium. We present numerical simulations for an effectively isotropic model and experimental results for a set of different
combinations of a Gaussian beam co-propagating incoherently with a beam of a more complex internal structure, such as a higher
order transverse laser mode. We discuss the different formation processes and the general properties of a variety of different
dipole-mode composite solitons and expand our investigations to the generation of a quadrupole-mode composite soliton.
Received: 1 December 2000 / Revised version: 12 January 2001 / Published online: 21 March 2001 相似文献
2.
The properties of electromagnetic waves propagating in a semibounded, nonlinear, ferromagnetic medium are investigated. It is shown that under certain conditions the interaction between the spin and electromagnetic waves results in the localization of volume polaritons near the surface. Self-localization of surface polaritons due to the nonlinear properties of the medium occurs thereby. The nonlinear Schrödinger equation for nonlinear surface and volume polaritons is derived, and the conditions under which solitons of these waves exist are determined. The wave intensity required to observe the predicted effects is estimated. 相似文献
3.
4.
Analytical formulae for the optimization of the process of low-power phase modulation in a quadratic nonlinear medium 总被引:1,自引:0,他引:1
We show that using the approximation of fixed intensity analytical formulae, describing the process of induced phase modulation for the beams involved in second-order nonlinear optical processes can be derived. Expressions that allow the optimization of the phase shifts experienced by the fundamental and generated waves are presented for nonlinear quadratic processes, second-harmonic generation and sum-frequency mixing. In the case of seeding at the generated wavelength, the phase shift of the fundamental wave is due to two interactions: (i) a cubic one, based on coupled second-order processes (cascade cubic nonlinearity) and (ii) single quadratic interaction with participation of the seeding wave. By comparison with the exact numerical solution, we defined the input parameters of the beams for which this analytical approach is valid. It is shown that phase shifts exceeding /2 can be correctly predicted using the expressions obtained. 相似文献
5.
The third-order nonlinear susceptibilities
xxx
(3)
(–3; 1, 1, 1) versus concentration are determined for rhodamine 6G, fuchsin, and methylene blue in methanol. Third-harmonic generation of a modelocked Nd-glass laser is applied. The real and imaginary part of the nonlinear susceptibility are measured. A resonance enhancement due to absorption bands is observed. 相似文献
6.
M. V. Belyayev V. P. Chebotayev A. P. Maiorov V. A. Smirnov 《Applied physics. B, Lasers and optics》1986,41(2):131-133
Observation of light scattering on the laser-produced temperature inhomogeneities, the centres of which are connected with some absorbing molecules, is reported. The experimentally observed scattering intensity agrees well theory. 相似文献
7.
E.R. Eliel E.W.M. van der Ham Q.H.F. Vrehen 《Applied physics. B, Lasers and optics》1999,68(3):349-353
Received: 23 December 1998 相似文献
8.
U. Langbein F. Lederer H. -E. Ponath U. Trutschel 《Applied physics. B, Lasers and optics》1985,36(4):187-193
The dispersion relations of TE-polarized nonlinear guided waves (NGW) were investigated in detail. These waves travel along a dielectric slab embedded between two different nonlinear media. A simple relation between the effective nonlinear dielectric constants was established. All dispersion curves exhibit a particular transition point, where one evanescent field maximum changes from a virtual into a real one, and vice versa. Depending on the type of the remaining invariant evanescent field maximum, all NGW's split into two families. The lowest-order membres of every family play a particular role. The power flux supported by a NGW is derived, too.Preliminary results were presented at the XVIth European Congress of Molecular Spectroscopy, Sofia, Bulgaria (1983) 相似文献
9.
U. Langbein F. Lederer H. -E. Ponath U. Trutschel 《Applied physics. B, Lasers and optics》1985,38(4):263-268
The dispersion relations of TE-polarized nonlinear guided waves (NGWs) in a symmetrical slab configuration (linear slab embedded between two identical media with a Kerr nonlinearity) are investigated in detail. Among even and odd NGWs the waveguide can support also NGWs, revealing an asymmetrical field pattern. The excitation of these NGWs requires a minimum guided power flux indicating a bifurcation of the corresponding dispersion curves. 相似文献
10.
We present a numerical model to study the wavefront of a Gaussian laser beam propagated through a nonlinear Kerr media. The model is based on the Gaussian decomposition method. The interaction between a laser beam and a self-focusing or self-defocusing media is discussed from the viewpoint of wavefront distortion. The method is useful for simulation of the wavefront of the beam next to the sample. We also compare our results with those obtained from z-scan method. There is a quite good agreement between data from z-scan method and our results. 相似文献
11.
Comparison between c-cut and a-cut Nd:YVO4 microchip lasers passively Q-switched with a Cr4+:YAG saturable absorber is experimentally made. The lower emission cross section of the c-cut Nd:YVO4 crystal can enhance the passive Q-switching effect to produce a peak power 10 times higher than that obtained with the a-cut
crystal. The experimental result further reveals that a c-cut Nd:YVO4 crystal is a very convenient material for short-pulse (sub-nanosecond) and high-peak-power (>10 kW) lasers.
Received:10December2001/Revisedversion:22January2002 / Published online: 14 March 2002 相似文献
12.
We observed circular white-light dark spatial solitons in photovoltaic self-defocusing LiNbO3:Fe crystal using an ordinary incandescent lamp as light source (a line source) with the filament of the bulb parallel to the crystalline c axis. Besides the above condition, the formation of the elliptic soliton needs an additive condition that the crystalline c axis is parallel to the minor axis of dark elliptic spot. 相似文献
13.
We found the dispersion relations for TM-polarized nonlinear waves guided by a dielectric film of thicknessd bounded on one side by a nonlinear uniaxial medium characterized by a dielectric tensor
xx
=
y
=
c
,
zz
=
c
+
c
|E
z
|2,
c
>0 (self-focusing medium),E
z
being the electric-field component perpendicular to the surfaces. Numerical calculations are given for the power dependence of the propagation wave vector. For sufficiently larged/ (: wavelength) we have found regions with multiple solutions corresponding to the same power flow. This suggests possible applications to optical devices. 相似文献
14.
Y. H. Ja 《Applied physics. B, Lasers and optics》1984,33(1):51-56
A theoretical study is presented of a special case of stationary energy transfer in degenerate two-wave mixing in a reflection geometry. The two interacting beams consist of a beam and its first-order internal reflection component created at the boundary of a nonlinear medium. Numerical results obtained from the computer calculations are presented as graphs. It is found that, under suitable conditions, this phenomenon can be used to eliminate the multiple internal reflections. 相似文献
15.
Wave front of a light pulse is shown to be unstable as it propagates through a resonant saturable absorber, if its frequency
is higher than the resonance frequency of the absorber. When ΔωT
2∼1, a small-scale transverse instability with the dimension of (λl
abs)1/2 grows rapidly. Its growth-rate is of the order of the small-signal-absorption length of the medium. 相似文献
16.
The coexistence of bistability and repetitive passive Q-switching of a CO2 laser with a gaseous saturable absorber has been investigated experimentally. With CH3F as the saturable absorber bistability has been observed simultaneously with passive Q-switching, whereas with CH3OH either one of these phenomena can only exist, as demonstrated for the first time. The measured features of both systems can be explained qualitatively by rate-equation theory. 相似文献
17.
When the relative phase of a surface nonlinear polarizability is measured by interference techniques, the resultant interferogram may be of lower contrast than that expected for ideal waves. It is shown, both theoretically and experimentally that this degradation arises from the multimode character of the pulsed lasers used. Differences between longitudinal and transverse mode effects are demonstrated. The laser coherence time may be deduced from the fringe degradation caused by longitudinal modes. 相似文献
18.
The dispersion relation for the plasmon at the interface of a metal and a nonlinear Kerr medium is studied by applying a semi-analytic theory established in the literature. Explicit analytical results are obtained and are compared to those from a certain approximate treatment appeared in the literature. It is found that for large electric field strengths, both the dispersion relation and the surface plasmon frequency from the approximate treatment deviate significantly from those obtained in the exact approach, especially for the case with a negative Kerr susceptibility. 相似文献
19.
We consider gravitational instability of saline boundary layers, observed at the subsurface of salt lakes. This boundary layer is the result of the convective transport induced by the evaporation at the horizontal surface of a confined porous medium. When this upward transport is balanced by salt dispersion, a steady state boundary layer is formed. However, this boundary layer can be unstable when perturbed. This results in complex groundwater motion and density fields. The aim of this paper is to investigate the existence of finite amplitude solutions describing these resulting patterns (both the number of solutions and their structure), their stability, and their dependency on the system Rayleigh and Péclet numbers. For this purpose we construct a low-dimensional dynamical system (a reduced model) by projecting the nonlinear model equations onto a relatively small set of eigenfunctions of the problem linearized at criticality. The Galerkin projection approach is complicated by the fact that the problem under consideration is non-self-adjoint due to the existing evaporation. This implies that the eigenfunctions do not form an orthogonal set and therefore the adjoint eigenfunctions are used for the projection. The reduced model is constructed in such a way that it is capable of providing solutions in the strongly nonlinear regime as well. Convergence of these solutions towards the fully nonlinear model results is shown by means of direct numerical simulations. Further, the reduced model seems to partly capture the complex nonlinear behavior as seen in Hele-Shaw experiments by Wooding et al. [R.A. Wooding, S.W. Tyler, I. White, P.A. Anderson, Convection in groundwater below an evaporating salt lake: 2. evolution of fingers or plumes, Water Resour. Res. 33 (6) (1997) 1219-1228]. The physical transition mechanism that explains the occurrence of some observed bifurcation types is presented as well. 相似文献
20.
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