Degenerate four-wave mixing in the presence of nonuniform pump wave fronts

We derive the set of coupled equations that describes the process of degenerate four-wave mixing in the presence of spatially nonuniform pump-beam wave fronts. We investigate the influence of phase mismatch between plane-wave pump beams on the efficiency and on the fidelity of the phase-conjugation process, and we furnish, in the near-collinear geometry, the expression of the spatial degree of coherence of the phase-conjugate wave in terms of those of the input signal and of the pump beams

Nonparaxial spatial solitons and propagation-invariant pattern solutions in optical Kerr media

We investigate nonlinear propagation in the presence of the optical Kerr effect by relying on a rigorous generalization of the standard parabolic equation that includes nonparaxial and vectorial terms. We show that, in the (1+1)-D case, both soliton and propagation-invariant pattern solutions exist (while the standard hyperbolic-secant function is not a solution)

An exact transverse Helmholtz equation

We derive an exact equation for the transverse component of the electric field propagating along a given longitudinal z direction in the presence of an isotropic refractive-index distribution n(x,y)

Nonparaxial dark solitons in optical Kerr media

We show that the nonlinear equation that describes nonparaxial Kerr propagation, together with the already reported bright-soliton solutions, admits of (1 + 1)D dark-soliton solutions. Unlike their paraxial counterparts, dark solitons can be excited only if their asymptotic normalized intensity u²_infinity is below 3/7; their width becomes constant when u²_infinity approaches this value

The case of the oscillating party balloon: A simple toy experiment requiring a not-so-simple interpretation

The intriguing midair oscillations of a party balloon, which occur once its buoyancy is no longer capable of keeping it against the ceiling, is shown to require a rather sophisticated explanation in terms of variable-mass dynamics. The ubiquity of this phenomenon, the accessibility of its actual observation, and the subtlety of its analytic description provide a good opportunity for an interesting zero-cost classroom demonstration

Vectorial nonparaxial propagation equation in the presence of a tensorial refractive-index perturbation

The standard scalar paraxial parabolic (FockLeontovich) propagation equation is generalized to include all-order nonparaxial corrections in the significant case of a tensorial refractive-index perturbation on a homogeneous isotropic background. In the resultant equation, each higher-order nonparaxial term (associated with diffraction in homogeneous space and scaling as the ratio between beam waist and diffraction length) possesses a counterpart (associated with the refractive-index perturbation) that allows one to preserve the vectorial nature of the problem (∇∇· E ≠ 0). The tensorial character of the refractive-index variation is shown to play a particularly relevant role whenever the tensor elements δnxz and δnyz (z is the propagation direction) are not negligible. For this case, an application to elasto-optically induced optical activity and to nonlinear propagation in the presence of the optical Kerr effect is presented

Perfect Optical Solitons: Spatial Kerr Solitons as Exact Solutions of Maxwell's Equations

We prove that spatial Kerr solitons, usually obtained in the frame of nonlinear Schroedinger equation valid in the paraxial approximation, can be found in a generalized form as exact solutions of Maxwell's equations. In particular, they are shown to exist, both in the bright and dark version, as linearly polarized exactly integrable one-dimensional solitons, and to reduce to the standard paraxial form in the limit of small intensities. In the two-dimensional case, they are shown to exist as azimuthally polarized circularly symmetric dark solitons. Both one and two-dimensional dark solitons exhibit a characteristic signature in that their asymptotic intensity cannot exceed a threshold value in correspondence of which their width reaches a minimum subwavelength value.Comment: 19 pages, 11 figure. Submitted for publication on Josa