Self-focussing in a vapour of two-state atoms

Boshier, M. G.; Sandle, W. J.

doi:10.1016/0030-4018(82)90251-6

Cited by 41 publications

(12 citation statements)

References 9 publications

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“…However, for E 0 = 0.006 mJ, we already have a pulse focused around z ≈ 0.15 m with the peak on-axis fluence over an order of magnitude greater than its initial (z = 0) value, despite absorption (panel (b), blue curve). The overall behavior is very similar to that found for laser propagation in a medium of resonant two-level atoms [11], where the nonlinear refractive index and saturable absorption were both found to contribute to self-focusing. (Note however, that those results were derived for CW beams and ionization completely absent.…”

Section: A Pulse Self-focusing and Self-channelingsupporting

confidence: 77%

“…At this point however, the medium is rendered almost transparent. All this means that we have a hybrid system -around the pulse edge, where intensity is small, we may expect phenomena familiar from resonant nonlinear optics [11][12][13][14]. On the other hand, around the pulse center where intensity is large we may expect processes similar to the ones encountered in filamentation studies [2,3,5,15].…”

Section: Introductionmentioning

confidence: 94%

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Propagation of ultrashort resonant ionizing laser pulses in rubidium vapor

Demeter

2019

Phys. Rev. A

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We investigate the propagation of ultra-short laser pulses in atomic rubidium vapor. The pulses are intensive enough to ionize the atoms and are directly resonant with the 780 nm D2 line. We derive a relatively simple theory for computing the nonlinear optical response of atoms and investigate the competing effects of strong resonant nonlinearity and ionization in the medium using computer simulations. A nonlinear self-channeling of pulse energy is found to produce a continuous plasma channel with complete ionization. We evaluate the length, width and homogeneity of the resulting plasma channel for various values of pulse energy and initial focusing to identify regimes optimal for applications in plasma-wave accelerator devices such as that being built by the AWAKE collaboration at CERN. Similarities and differences with laser pulse filamentation in atmospheric gases are discussed.

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Section: A Pulse Self-focusing and Self-channelingsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 94%

Propagation of ultrashort resonant ionizing laser pulses in rubidium vapor

Demeter

2019

Phys. Rev. A

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“…Specifically, we consider light propagation in two-state homogeneously broadened atomic vapor [21,22]. Such medium may exhibit a strong saturation as well as nonlocality.…”

Section: Saturation-mediated Stabilizationmentioning

confidence: 99%

Stabilization of dipole solitons in nonlocal nonlinear media

Kartashov

Torner

2008

Phys. Rev. A

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We address the stabilization of dipole solitons in nonlocal nonlinear materials by two different approaches. First, we study the properties of such solitons in thermal nonlinear media, where the refractive index landscapes induced by laser beams strongly depend on the boundary conditions and on the sample geometry. We show how the sample geometry impacts the stability of higherorder solitons in thermal nonlinear media and reveal that dipole solitons can be made dynamically stable in rectangular geometries in contrast to their counterparts in thermal samples with square cross-section. Second, we discuss the impact of the saturation of the nonlocal nonlinear response on the properties of multipole solitons. We find that the saturable response also stabilizes dipole solitons even in symmetric geometries, provided that the input power exceeds a critical value.

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“…Subsequent work by other groups improved the understanding of these experiments by treating the atomic medium as an ensemble of two-level atoms [15][16][17][18]. Yabuzaki, Hori, and Kitano [ 19] suggested that optical pumping with circularly polarized light should cause self-focusing at even lower power.…”

mentioning

confidence: 99%

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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Self-focussing in a vapour of two-state atoms

Cited by 41 publications

References 9 publications

Propagation of ultrashort resonant ionizing laser pulses in rubidium vapor

Propagation of ultrashort resonant ionizing laser pulses in rubidium vapor

Stabilization of dipole solitons in nonlocal nonlinear media

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

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