Optical Beams In Media Research Articles

Dynamics of Airy beams in nonlinear media

The dynamics of truncated Airy beams in optical media with Kerr nonlinearity is studied in the framework of the nonlinear Schr\odinger (NLS) model. It is demonstrated that an intense Airy beam with zero total momentum can generate static solitons, as well as moving solitons. The parameters of these solitons are calculated using the Zakharov-Shabat scattering problem associated with the NLS equation. It is found that solitons take the main part of the initial power, while only a small fraction of the power is transformed into a self-accelerating linear packet. The threshold parameters of the Airy beam for the soliton formation are obtained. It is shown that the threshold for the formation of the first static soliton is also a threshold of the solitonless regime.

Mutual repulsion of optical beams in media with nonlocal nonlinearity

Mutual repulsion of optical beams in media with nonlocal nonlinearity

Bistable Helmholtz solitons in cubic-quintic materials

We propose a nonlinear Helmholtz equation for modeling the evolution of broad optical beams in media with a cubic-quintic intensity-dependent refractive index. This type of nonlinearity is appropriate for some semiconductor materials, glasses, and polymers. Exact analytical soliton solutions are presented that describe self-trapped nonparaxial beams propagating at any angle with respect to the reference direction. These spatially symmetric solutions are, to the best of our knowledge, the first bistable Helmholtz solitons to be derived. Accompanying conservation laws (both integral and particular forms) are also reported. Numerical simulations investigate the stability of the solitons, which appear to be remarkably robust against perturbations.

Optical Beams in Media with Spatial Dispersion

We theoretically predict a novel phenomenon of thediffraction-free propagation of the paraxial optical beam in theisotropic or cubic linear medium with spatial dispersion. Underthe weak spatial dispersion condition, the paraxial wave equationis derived, in which there is the diffraction term with thecoefficient Γ that depends on the compensationbetween the classic diffraction and spatial dispersion. Near theexciton dipole absorption line, we can have Γ = 0, then thebeam propagates diffraction-freely, and its shape keepsunchangeable. Discussed are also the physical mechanism and thepossible experimental candidates of crystals for the phenomenon.

Collision of solitary waves in media with a second-order nonlinearity.

We consider the collision behavior of self-trapped optical beams in media with a quadratic nonlinearity. It is found that the solitary waves behave similarly to true solitons above a critical velocity. Below this velocity they merge and form oscillating states.

NON-LAGRANGIAN NONLINEARITY AND COHERENT OPTICAL WAVE MIXING PROCESSES

Interaction of optical beams in media with diagonal-bipolar nonlinearity is theoretically investigated. It is shown that the nonlinearity is not Lagrangian and allows processes violating energy flux conservation law. Conditions for energy exchange to take place are found. Probe beam amplification in the field of counterpropagating pumps and wavefront conjugation are investigated to exhibit some remarkable features. Coherent interaction of waves of different frequencies through recording static gratings is shown to lead also to energy exchange processes owing to non-Lagrangian character of nonlinearity.

Wave-kinetic numerical approach to propagation of optical beams

A new method is proposed for calculating the propagation of optical beams in media with slowly (and possibly randomly) varying refractive indices. It utilizes the conservation of the Wigner distribution function in the Liouville approximation along the beam trajectories and discretizes this quantity into a number of four-dimensional Gaussians so that each one retains its Gaussian character along the trajectories. The irradiance is then obtained by analytical integration of wave-vector coordinates over a sum of Gaussians. Conditions are specified for the region of applicability.

Spiral self-trapping propagation of optical beams in media with cubic nonlinearity

A new (three-dimensional) type of self-trapped beam connected with the rotation of the field phase is obtained. It is shown that the field intensity is ring-shaped, and the field distribution has a rotating spiral character, its parameters being expressed through constants of the motion. Existence conditions for such spiral-like beams are indicated.

The application of Gaussian beam. Formalism to optical propagation in nonlinear media

The nonlinear propagation problem of optical beams in media with an intensity dependent indices of refraction is solved in the case of a fundamental gaussian beam. This solution is made possible by assuming everywhere along the propagation path a quadratic index profile. The quadratic constant is obtained self-consistently from the second term in a Taylor expansion of the local gaussian intensity. The solution constitutes an extension of the well known ABCD formalism to nonlinear propagation.