Dynamics of self-focusing and self-phase modulation in a parabolic index optical fiber (original) (raw)
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Dynamics of self-focusing and self-phase modulation of elliptic Gaussian laser beam in a Kerr-medium
Pramana, 2000
Using a direct variational technique involving elliptic Gaussian laser beam trial function, the combined effect of non-linearity and diffraction on wave propagation of optical beam in a homogeneous bulk Kerr-medium is presented. Particular emphasis is put on the variation of beam width and longitudinal phase delay with the distance of propagation. It is observed that no stationary self-trapping is possible. The regularized phase is also seen to be always negative.
Optics Express
Beam self-imaging in nonlinear graded-index multimode optical fibers is of interest for many applications, such as implementing a fast saturable absorber mechanism in fiber lasers via multimode interference. We obtain an exact solution for the nonlinear evolution of first and second order moments of a laser beam carried by a graded-index multimode fiber, predicting that the spatial self-imaging period does not vary with power. Whereas the amplitude of the oscillation of the beam width is power-dependent. We have experimentally studied the longitudinal evolution of beam self-imaging by means of femtosecond laser pulse propagation in both the anomalous and the normal dispersion regime of a standard telecom graded-index multimode optical fiber. Light scattering out of the fiber core via visible fluorescence emission and harmonic wave generation permits us to directly confirm that the self-imaging period is invariant with power. Spatial shift and splitting of the self-imaging process under the action of self-focusing are also emphasized.
Light guiding in optical fibers with Kerr-like nonlinearity
Microwave and Optical Technology Letters, 2001
Guiding properties of optical fiber with Kerr-like nonlinearity are studied numerically using the finite-difference beam-propagation method to sol¨e the scalar-wa¨e equation. The nonlinear fiber is shown to support fields with longitudinally in¨ariant radial distributions ha¨ing a mean-squared beam width less than that of the linear fiber mode. The double-mode propagation is shown to be unstable, and tends to con¨ert into single-mode propagation after some distance from the input endface of the fiber. ᮊ
Journal of the Optical Society of America B, 2008
An exact solution describing the self-similar dynamics of partially coherent light beams in nonlinear and noninstantaneous Kerr media is presented and analyzed. The description is based on the Wigner formalism for analyzing the propagation of partially coherent light. The solution for the Wigner distribution corresponds to a transverse beam intensity profile of a parabolic form, and the effects of the partial coherence on the beam dynamics are analyzed. The presence of partial coherence in the parabolic beam is shown to increase the diffraction effect, thus weakening the nonlinear self-focusing and increasing the defocusing rate. In the case of an almost coherent beam and a strongly nonlinear situation in a defocusing medium, the new solution is shown to reduce to a previously given parabolic similarity solution for coherent high intensity beam-pulse propagation.
Stable propagation of pulsed beams in Kerr focusing media with modulated dispersion
Journal of the Optical Society of America B, 2006
We propose the modulation of dispersion to prevent collapse of planar pulsed beams which propagate in Kerr-type self-focusing optical media. As a result, we find a new type of two-dimensional spatio-temporal solitons stabilized by dispersion management. We have studied the existence and properties of these solitary waves both analytically and numerically. We show that the adequate choice of the modulation parameters optimizes the stabilization of the pulse.
Observation of spatial cross-phase modulation effects in a self-defocusing nonlinear medium
Physical Review Letters, 1992
We report on experimental observations of spatial modifications, induced by the Kerr effect, in the profile of a weak probe beam due to a cross-phase modulation from a strong pump beam. The measurements were performed in a self-defocusing nonlinear medium (semiconductor doped glass) where the observation of induced focusing and spatial modulation instability were made possible. The experimental results are in good agreement with numerical simulations.
Optical Beam Propagation in Nonlinear Media
2008
his article addresses several types of optical beams, and their propagation along different media. Initially, the proprieties and the evolution of the Gaussian beam propagating through a homogeneous linear media are studied using the paraxial approximation. The results allow the understanding of more complex beams, e.g., rectangular and hyperbolic secant profiles, which are analyzed using a numerical method based on the Fast Fourier Transform (FFT). Taking into account the properties of the simpler beams, the Hermite – Gaussian high order beams are subsequently studied, using the time independent Schrödinger equation and the solutions of the quantum harmonic oscillator. After this, a brief analysis of the propagation of the Hermite – Gaussian beams through an anisotropic media is done. In the presence of nonlinear media the Gaussian, the Hermite – Gaussian and the existence of spatial solitons are studied, the lately bearing in mind their behavior under the influence of self – focus...
Propagation of ellipitic Gaussian laser beam in a higher order non-linear medium
Optik - International Journal for Light and Electron Optics, 2004
Using a direct variational technique involving elliptic Gaussian laser beam trial function, the combined effect of nonlinearity and diffraction on wave propagation of optical beam in a homogeneous higher order nonlinear medium is presented. Particular emphasis is put to understand the variation of beam width and longitudinal phase delay with the distance of propagation in case of lossless and lossy medium. It is also observed that stationary self-trapping is possible in lossless medium at higher laser intensity where fifth order nonlinearity becomes comparable to third order nonlinearity. The phase is also seen to be always negative.
Propagation of laser vortex beams in a parabolic optical fiber
Optical Technologies for Telecommunications 2009, 2009
We discuss the propagation of monochromatic light vortex beams in a medium with minor nonuniformities of the refractive index. The propagation of the light beams is modeled by two methods -using a paraxial integral operator and through the decomposition in the parabolic medium modes.