Kaleidoscopic spatial instability: Bifurcations of optical transverse solitary waves

Grantham, J. W.; Gibbs, H. M.; Khitrova, G.; Valley, J. F.; Xu, Jinghui

doi:10.1103/physrevlett.66.1422

Cited by 46 publications

(13 citation statements)

References 17 publications

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“…We observed ring structures, splitting of the beam into two partial beams, as well as more complicated structures. These instabilities resemble closely the kaleidoscopic spatial instabilities which Grantham et al observed by introducing aberrations into the beam [33]. They indicate that the stabilization of the self-trapped beam by the saturation process and t.he nonlinear response of the medium is effective only in a limited parameter range.…”

Section: ~ Dieter Suter and Tilo Blasbergsupporting

confidence: 63%

Stabilization of transverse solitary waves by a nonlocal response of the nonlinear medium

1993

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Optical pumping of atomic vapors can lead to self-focusing of resonant laser beams. The saturation of the optical pumping process at low intensity allows the study of transverse solitons in the form of selftrapped laser beams, using low-power cw lasers. The long lifetime of the optically pumped atoms allows the atomic diffusion to transport the excitation away from the interaction region. Numerical simulations show that the resulting nonlocal response of the medium represents an important mechanism that stabilizes the self-trapped beam. The theoretical predictions are confirmed by experimental results from sodium vapor. PACS number(s): 42.65.Jx, 42.5O.Rh Self-focusing of laser beams in nonlinear optical media [1][2][3] is one of the best examples of spontaneous formation of (spatially) localized structures due to nonlinear processes. Self-focusing occurs if the total index of refraction increases with the laser intensity, as in many Kerr media. Laser beams with Gaussian intensity profiles then induce a refractive index profile, which has the same effect as a convex lens, thereby counteracting the normal effect of diffraction. When the two effects cancel each other, the beam can propagate without diffraction; it is then said to be self-trapped [4,5]. Since both the Kerr effect leading to self-focusing and the opposing tendency of light to diffract are indirectly proportional to the cross-sectional area of the beam, the selftrapped state is unstable in ideal three-dimensional Kerr media [3,6]. If the laser intensity is below a critical intensity that depends on the nonlinearity of the medium, the beam diffracts as usual. Above the critical intensity, the beam self-focuses to an area of the dimension of the optical wavelength [7], unless damage to the material stops the process [2]. At the critical intensity, the beam can propagate without diffracting, but arbitrarily small perturbations cause it to fall into either of the two other regimes. In two-dimensional systems, such as planar waveguides, self-trapped beams can be stable and lead to nondiffracting beams [8-l0]. In analogy to other stable, localized solutions of nonlinear wave equations, such self-trapped beams have been called "spatial solitary waves" or "transverse solitons." While Derrick's theorem [6] precludes the existence of stable, time-independent solutions of nonlinear wave equations that are localized in more than one spatial dimension, it is well known [3] that laser beams can be self-trapped in three-dimensional media, when the index of refraction does not increase indefinitely with intensity, but saturates before the material suffers laser-induced damage. In such a medium, the laser beams can become localized in the two transverse dimensions. In general, its diameter is not time independent, but shows characteristic oscillations that reflect the competing effects of selffocusing and diffraction [3, 1 1,12]. This saturation effect had already been proposed as the relevant mechanism for the formation of the small-scale filaments that tend to form ...

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Section: ~ Dieter Suter and Tilo Blasbergsupporting

confidence: 63%

Stabilization of transverse solitary waves by a nonlocal response of the nonlinear medium

1993

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“…This regime valid for larger optical thickness will be considered in this letter. Note that in contrast to past observation of pattern formation in hot atomic vapors [19,20] the instabilities based on the coupling to the atomic motion do not require non linear optical response of the atoms.…”

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confidence: 81%

Observation of a Cooperative Radiation Force in the Presence of Disorder

et al. 2010

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We show that static and oscillating photon bubbles can be excited by diffused light in the laser cooled matter confined in a magneto-optical trap (MOT). The bubble instability is due to the coupling between the radiation field and the mean field oscillations of the ultra-cold gas, and it can provide a source for low frequency turbulence. We consider a diffusion dominated regime, which can be described by a radiation transport equation, coupled with the mean field equations for the cold atom gas. A perturbative analysis shows the occurrence of two different regimes with either oscillating or purely growing bubbles. This work could also be useful to understand similar processes in astrophysics.

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“…This may be done via an 552 H.-G. Purwins et al 5a. R 2 Alkali vapours in an extended cells Figure 47(a) [283][284][285][286][287][288][289] Stat. pattern in the laboratory system Self-focussing One or more entering beams with vanishing and nonvanishing vorticity Along optical axis: rotation, clusters, fusion, breakup into many spots, interaction of LSs D % 50 mm additional dye cell at position 3 that in turn is pumped by an external laser 4 [260].…”

Section: Saturable Absorbersmentioning

confidence: 99%