Self-trapped Light Beams Research Articles

3-D Spiraling Self-Trapped Light Beams in Photochemical Systems.

A pair of visible laser beams self-trap and spiral about each other as they propagate through polymer gels undergoing two different photochemical reactions. When launched into gels that undergo photopolymerization of methacrylate substituents or photo-oxidation of iodide anion, two non-coplanar (skewed) Gaussian beams collide and spiral about each other as they advance through the evolving medium. In the absence of chemical reactions, the linearly polarized beams broaden naturally and propagate along their original, straight-pathed trajectories. By contrast, refractive index gradients generated by the photochemical reactions elicit self-trapping and introduce an attractive interaction between the self-trapped beams. The self-trapped beams spiral about each other when this mutual attraction perfectly counterbalances their original tendency to diverge away from each other. These findings show that the photochemically mediated interactions of incident optical fields within the gel medium impart a helical trajectory and angular velocity to the self-trapped beam pair.

Accessible Light Bullets via Synergetic Nonlinearities

We introduce a new form of stable spatiotemporal self-trapped optical packets stemming from the interplay of local and nonlocal nonlinearities. Pulsed self-trapped light beams in media with both electronic and molecular nonlinear responses are addressed to prove that spatial and temporal effects can be decoupled, allowing for independent tuning. We numerically demonstrate that (3 + 1)D light bullets and antibullets, i.e., bright and dark temporal solitons embedded in stable (2 + 1)D nonlocal spatial solitons, can be generated in reorientational media under experimentally feasible conditions.

Nematicons: Optical Spatial Solitons in Nematic Liquid Crystals

Nematicons are self-trapped light beams in nematic liquid crystalline systems. Thanks to their optically nonlinear, saturable, nonlocal and nonresonant response, they enable light to self-confine and guide additional optical signals, making them an ideal testbed for applications in all-optical information processing.

CYLINDRICAL TM-MODES IN A HOMOGENEOUS SELF-FOCUSING DIELECTRIC

This paper deals with the mathematical analysis of self-trapped light beams in a homogeneous medium which has a self-focusing dielectric response. We consider modes where the electromagnetic fields have a cylindrical symmetry and the magnetic field is transverse to the direction of propagation. The main results establish a range of wavelengths for which such guided modes exist. The behavior of the power of the beam as the wavelength approaches its extreme values is also determined. The existence of self-trapped modes is established using a variational principle. Bounds on the wavelength and the power are obtained directly from the associated quasilinear eigenvalue problem.

TE and TM families of self-trapped beams

TE and TM families of self-trapped light beams with circular cross section are examined. First, trapped TE/sub 0m/ modes with rotational symmetry are investigated analytically using a variational technique to obtain approximate analytical expressions for the field profiles and modal propagation constants. It is shown that trapped TE/sub 0m/ modes are unstable; they diffract below the critical trapping powers and focus to thin rings above the critical trapping powers. It is demonstrated that there exists a class of self-trapped beams with rotational symmetry, TM/sub 0m/ modes which can be trapped in the self-induced circular waveguides over a continuous range of power values, in contrast to TE/sub 0m/ modes trapped only at critical powers. Furthermore, the lowest order TM type of beam is found to be stable. >

Moment theory of self-trapped laser beams with nonlinear saturation

The moment theory of the quasi-optical equation is used to obtain simple analytical expressions for the relation between beam radius and power of stationary self-trapped light beams in passive nonlinear media with saturation of the index of refraction. In addition, the stability of these self-trapped beams is determined.

On noncircularly symmetric self-trapped light beams

Self-trapping solutions of the nonlinear scalar wave equation with arbitrary transverse symmetry (e.g., elliptical) do not exist.

Vectorial theory of self-trapped light beams

Nonlinear optical media may support self-trapped “filaments” with transverse electric (TE), transverse magnetic (TM), or hybrid (HE and EH) field configurations. The divergence of the electric field vanishes in a certain class of configurations thereby introducing a simple criterion for their existence. The HE 11, TE 0 q and TM 0 q filaments, distinguished by a high degree of symmetry, are discussed in detail. Of these, only the TE 0 q type allows for well-defined modes consisting of tubular beams of light.

Interaction of Self-trapped Light Beams

PRELIMINARY experiments have been carried out on the interaction of two self-trapped light beams in water. The 200 MW, 20 nsec output from a Q-switched ruby laser* was split by prisms and focused into a glass cell containing water to form two self-trapped beams (Fig. 1). Photographs were taken using the light scattered sideways from these beams.

Narrow optical waveguides and instabilities induced in liquids

Self-trapped light beams having a 4μ diameter, a power density ⩾ 4GW/cm 2, and a 0.5 nsec duration are observed in liquids. Instability effects, saturation in stimulated scattering processes, and the origin of the intensity-dependent refractive index are discussed.