Transverse ‘‘bouncing’’ of polarized laser beams in sodium vapor

Holzner, R.; Eschle, P.; Aw, McCord; Dm, Warrington

doi:10.1103/physrevlett.69.2192

Cited by 21 publications

(7 citation statements)

References 4 publications

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“…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. Within this parameter range, however, self-trapped beams cannot only propagate with an invariant cross section, but it is even possible that beams with different polarizations bounce off each other [34].…”

Section: ~ Dieter Suter and Tilo Blasbergmentioning

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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Section: ~ Dieter Suter and Tilo Blasbergmentioning

confidence: 99%

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

1993

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“…Furthermore the model assumes the magnetic fields to be homogeneous whereas we measured residual ac and dc magnetic stray fields of about A3 mG along the beam path through the cell, using a 3-axis magnetic-field sensor (MAG-03-MC from Bartington). Some of these differences can be removed when the fiull model [14,12] is used. This semiclassical model does include saturation, dsraction, optical pumping, and beam propagation effects and therefore fully accounts for the Gaussian intensity distribution of the laser beams as well as for the nonuniform intensity distribution along the sodium cell.…”

Section: Experimental Result's and Discussionmentioning

confidence: 99%

“…2 we used parameter values, which correspond to an experimental setup described in [12,13]: ao=548 rn-', Ro=l.2X106 S-', yo=2.5X103 s-l, g=2rX7X105 s-* G-l, Po=(3*1) mW input power of u+, cr _, or linearly polarized beams, UJ~ =(230&10) pm beam waist at the input window of the sodium vapor cell, L =(6i5ztO. 11 cm length of the sodium vapor cell, rzN8 =(2.5*0.5) X lOi mm3 density of sodium atoms at T =2OO'C cell temperature, n& = (8311) X lO24 mm3 density of argon atoms at p ~250 Torr buffer gas pressure, and F=( l.OkO.…”

Section: Calcula'i'ionsmentioning

confidence: 99%

Large frequency shifts of absorption profiles due to the combination of optical pumping, light shift, and magnetic fields in sodium vapor

et al. 1994

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The absorption profiles of left-hand and right-hand circularly polarized laser light propagating through sodium vapor are asymmetric and considerably frequency shifted if small static magnetic fields are present. Using an analytical model we show how optical pumping "enhances" the laser-induced light shift from the kilohertz to the gigahertz range. We compare the analytical results with experimental data obtained from the homogeneously broadened Na D 1 , transition.

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“…The laser beam is spatially filtered to have a residual astigmatism of less than 1%. viation from cylindrical symmetry has developed, it is drastically amplified by the effect of mutual beam deflection already described in [8].…”

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confidence: 96%

Self-induced planar and cylindrical splitting of a laser beam in sodium vapor

et al. 1994

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An almost linearly polarized laser beam focused into a sodium vapor cell may split into different patterns ranging from two spots to a spot and a ring of opposite circular polarization. The patterns are controlled by static magnetic fields of the order of the earth s field. The behavior is explained, allowing for a longitudinal component of the dielectric polarization in the paraxial wave equation. Numerical results reveal the delicate balance between light shift, inhuence of the magnetic field, and the creation of ground-state orientation by the competing polarization components.PACS number(s): 42.50.Ne, 42.50. 6y, 42.65.An

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Transverse ‘‘bouncing’’ of polarized laser beams in sodium vapor

Cited by 21 publications

References 4 publications

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

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

Large frequency shifts of absorption profiles due to the combination of optical pumping, light shift, and magnetic fields in sodium vapor

Self-induced planar and cylindrical splitting of a laser beam in sodium vapor

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