共查询到20条相似文献,搜索用时 796 毫秒
1.
L. M. Kovachev L. I. Pavlov L. M. Ivanov D. Y. Dakova 《Journal of Russian Laser Research》2006,27(3):185-203
We have investigated the evolution of picosecond and femtosecond optical pulses governed by the amplitude vector equation
in the optical and UV domains. We have written this equation in different coordinate frames, namely, in the laboratory frame,
the Galilean frame, and the moving-in-time frame and have normalized it for the cases of different and equal transverse and
longitudinal sizes of optical pulses or modulated optical waves. For optical pulses with a small transverse size and a large
longitudinal size (optical filaments), we obtain the well-known paraxial approximation in all the coordinate frames, while
for optical pulses with relatively equal transverse and longitudinal sizes (so-called light bullets), we obtain new non-paraxial
nonlinear amplitude equations. In the case of optical fields with low intensity, we have reduced the nonlinear amplitude vector
equations governing the light-bullet evolution to the linear amplitude equations. We have solved the linear equations using
the method of Fourier transform. An unexpected new result is the relative stability of light bullets and the significant decrease
in the diffraction enlargement of light bullets with respect to the case of long pulses in the linear propagation regime. 相似文献
2.
We show that small negative fourth-order dispersion can arrest spatiotemporal collapse of ultrashort pulses with anomalous dispersion in a planar waveguide with pure Kerr nonlinearity, resulting in (2 + 1)D optical bullets. Similarly to solitons, these bullets undergo elastic collisions. Since these bullets can self-trap from noisy Gaussian input beams and propagate without any power losses, this result may be used to realize experimentally stable, nondissipative optical bullets. 相似文献
3.
W. B. Fraga J. W. M. Menezes C. S. Sobrinho A. C. Ferreira G. F. Guimar?es A. W. Lima Jr. A. F. G. F. Filho H. H. B. Rocha K. D. A. Sabóia F. T. Lima J. M. S. Filho A. S. B. Sombra 《Optical and Quantum Electronics》2009,41(2):121-130
In this paper, we have presented a numerical analysis of the stability of optical bullets (2 + 1), or spatiotemporal solitons (2 + 1), in a planar waveguide with cubic–quintic nonlinearity. The optical spatiotemporal solitons are the result of the balance between the nonlinear parameters, of dispersion (dispersion length, L D) and diffraction (diffraction length, L d) with temporal and spatial auto-focusing behavior, respectively. With the objective of ensure the stability and preventing the collapse or the spreading of pulses, in this study we explore the cubic–quintic nonlinearity with the optical fields coupled by cross-phase modulation and considering several values for the non linear parameter α We have shown the existence of stable light bullets in planar waveguide with cubic–quintic nonlinearity through the study of spatiotemporal collisions of the light bullets. 相似文献
4.
Lehner T Auby N 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(2):1996-2005
The nonlinear propagation of ultrashort laser pulses launched into the air is investigated. The formation of optical light "bullets," or spatially localized structures, has been experimentally observed recently. Their stability is shown as due to the occurrence of a dynamical balance between two opposite nonlinear effects: an optical focusing Kerr effect balanced by a defocusing self-induced multiphoton partial ionization of the neutral gas. Characteristics of the "bullets" are predicted analytically and confirmed numerically. They are found to be in agreement with observations. 相似文献
5.
Propagation of two- and three-dimensional ultimately short optical pulses (light bullets) in a medium exhibiting modulated refractive index and containing carbon nanotubes with a metallic type of conductivity is investigated theoretically. The dynamics of such pulses is demonstrated as a function of Bragg medium parameters. It is confirmed that the pulses are influenced by the state of the medium. 相似文献
6.
Three-Dimensional Extremely Short Optical Pulses of Airy in a Photonic Crystal with Carbon Nanotubes
Optics and Spectroscopy - The problem of the propagation dynamics of three-dimensional optical Airy pulses (light bullets) in a photonic crystal with carbon nanotubes is considered. It is... 相似文献
7.
The problem of dynamics of propagation of extremely short optical pulses (light bullets) with a Bessel cross section in inhomogeneous medium of carbon nanotubes has been considered. It is numerically shown that the optical pulse propagation is stable and steady. 相似文献
8.
We demonstrate the realization of intense Airy-Airy-Airy (Airy(3)) light bullets by combining a spatial Airy beam with an Airy pulse in time. The Airy(3) light bullets belong to a family of linear spatiotemporal wave packets that do not require any specific tuning of the material optical properties for their formation and withstand both diffraction and dispersion during their propagation. We show that the Airy(3) light bullets are robust up to the high intensity regime, since they are capable of healing the nonlinearly induced distortions of their spatiotemporal profile. 相似文献
9.
Physics of the Solid State - The theoretical problem of propagation dynamics of ultrashort optical pulses (light bullets) in a medium with inhomogeneous density of carbon nanotubes is considered.... 相似文献
10.
We demonstrate that propagation direction and velocity of optical pulses can be controlled independently in the structures with multiscale modulation of the refractive index in transverse and longitudinal directions. We reveal that, in arrays of waveguides with phase-shifted Bragg gratings, the refraction angle does not depend on the speed of light, allowing for efficient spatial steering of slow light. In this system, both spatial diffraction and temporal dispersion can be designed independently, and we identify the possibility for self-collimation of slow light when spatial diffraction is suppressed for certain propagation directions. We also show that broadening of pulses in space and time can be eliminated in nonlinear media, supporting the formation of slow-light optical bullets that remain localized irrespective of propagation direction. 相似文献
11.
Mads Peter Srensen Moysey Brio Garry M. Webb Jerome V. Moloney 《Physica D: Nonlinear Phenomena》2002,170(3-4):287-303
We present a numerical study of Maxwell’s equations in nonlinear dispersive optical media describing propagation of pulses in one Cartesian space dimension. Dispersion and nonlinearity are accounted for by a linear Lorentz model and an instantaneous Kerr nonlinearity, respectively. The dispersion relation reveals various asymptotic regimes such as Schrödinger and KdV branches. Existence of soliton-type solutions in the Schrödinger regime and light bullets containing few optical cycles together with dark solitons are illustrated numerically. Envelope collapse regimes of the Schrödinger equation are compared to the full system and an arrest mechanism is clearly identified when the spectral width of the initial pulse broadens beyond the applicability of the asymptotic behavior. We show that beyond a certain threshold the carrier wave steepens into an infinite gradient similarly to the canonical Majda–Rosales weakly dispersive system. The weak dispersion in general cannot prevent the wave breaking with instantaneous or delayed nonlinearities. 相似文献
12.
T. Konishi H. Furukawa Y. Ichioka K. Nakagawa M.R. Melloch D.D. Nolte 《Optical and Quantum Electronics》2001,33(7-10):1063-1076
To realize an ultra-fast spatio-temporal photonic interface system, we propose direct time–space conversion of ultra-fast pulses based on the interferometric time-of-flight cross correlation technique using a fast optical addressable spatial light modulator (OA-SLM). We show preliminary experiments using transverse-field photorefractive MQW devices as an OA-SLM compatible with ultra-fast pulses. 相似文献
14.
Minardi S Eilenberger F Kartashov YV Szameit A Röpke U Kobelke J Schuster K Bartelt H Nolte S Torner L Lederer F Tünnermann A Pertsch T 《Physical review letters》2010,105(26):263901
We report the first experimental observation of three-dimensional light bullets, excited by femtosecond pulses in a system featuring quasi-instantaneous cubic nonlinearity and a periodic, transversally modulated refractive index. Stringent evidence of the excitation of light bullets is based on time-gated images and spectra which perfectly match our numerical simulations. Furthermore, we reveal a novel evolution mechanism forcing the light bullets to follow varying dispersion or diffraction conditions, until they leave their existence range and decay. 相似文献
15.
Interactions between optical bullets with different velocities in the three-dimensional cubic-quintic complex Ginzburg-Landau equation 下载免费PDF全文
By using the three-dimensional complex Ginzburg--Landau
equation with cubic--quintic nonlinearity, this paper numerically
investigates the interactions between optical bullets with different
velocities in a dissipative system. The results reveal an
abundance of interesting behaviours relating to the velocities of
bullets: merging of the optical bullets into a single one at small
velocities; periodic collisions at large velocities and
disappearance of two bullets after several collisions in an
intermediate region of velocity. Finally, it also reports that an
extra bullet derives from the collision of optical bullets when
optical bullets are at small velocities but with high
energies. 相似文献
16.
R. A. Ganeev 《Optics and Spectroscopy》2016,120(5):766-772
Various laser-produced metal plasmas were used for high-order sum and difference harmonic generation using the mixing of tunable mid-infrared pulses from optical parametric amplifier and 810 nm ultrashort pulses. We show that, regardless of non-optimal spatio-temporal overlap of two sources of radiation in the plasmas, the application of proposed technique allows a significant growth of harmonic yield and broadening of the number of different combinations of interacting waves in the extreme ultraviolet region, which could be useful for observation of the resonance induced enhancement of some frequency components. 相似文献
17.
In quadratic nonlinear media with normal dispersion and nonvanishing group velocity mismatch between fundamental wave and second-harmonic pulses, the wave packets of two harmonics can be locked together in propagation in the form of walking X-shaped light bullets. The output wave packets are developed into X-shaped light bullets with significant group delay time due to mutual dragging and significant shifting in spatiotemporal spectrum due to delayed nonlinear phase shift. We also show that spontaneously generated phase-front tilting can balance the dragging force induced by group velocity mismatch and lead to zero-velocity walking X-shaped light bullets. 相似文献
18.
S. V. Sazonov 《Journal of Experimental and Theoretical Physics》2014,119(3):423-437
Soliton-like regimes of propagation of broadband terahertz pulses in a system of tunnel junctions have been theoretically studied taking into account the effect of quantum states higher in energy. This study has been performed beyond the approximation of slowly varying amplitudes standard for quasimonochromatic signals. It has been shown that the role of higher lying states is fundamentally important and is not reduced only to correction effects. Previously unknown soliton-like regimes of propagation, as well as the corresponding dynamics of a medium, have been analyzed. Nonlinear refraction processes have been taken into account. Conditions for self-focusing and defocusing of pulses have been revealed. A new type of localized terahertz “bullets” with sharp boundaries at a nonequilibrium initial population of tunneling states has been predicted. The main difference of these bullets from those previously considered in an optical range is that diffraction does not affect the formation of the former. In this case, the focusing effect caused by a tunneling transition is compensated by the defocusing effect of transitions to higher lying states under the conditions of applicability of the geometrical optics approximation. 相似文献
19.
Naum K. Berger 《Optics Communications》2010,283(7):1397-1405
We propose a method for the measurement of periodic optical waveforms based on the use of an electrooptic phase modulator placed in an optical Fabry-Perot or ring resonator. Significant broadening of the modulation spectrum extends the recently developed method of periodic modulation for pulse characterization into femtosecond scales. We numerically demonstrate the characterization of a 300-fs optical pulse. We also present a technique based on the temporal fractional Talbot effect for restoration of the pulse phase profile. After fast linear processing, subpicosecond pulses will be observed on the screen of a real-time oscilloscope. This complete characterization of optical pulses is entirely linear and therefore highly sensitive and simple in implementation. 相似文献
20.
We consider the paraxial model for a nonlinear resonator with a saturable absorber beyond the mean-field limit. For accessible parametric domains we observe total radiation confinement and the formation of 3D localized bright structures. Different from freely propagating light bullets, here the self-organization proceeds from the resonator feedback, combined with diffraction and nonlinearity. Such "cavity" light bullets can be independently excited and erased by appropriate pulses, and once created, they endlessly travel the cavity round-trip. 相似文献