Biomedical subjects

Sergey A Ponomarenko

Publications and source records attributed to Sergey A Ponomarenko.

5 recordsLinked to original sources

PubMed2006

Do solitonlike self-similar waves exist in nonlinear optical media?

We show analytically that bright and dark spatial self-similar waves can propagate in graded-index amplifiers exhibiting self-focusing or self-defocusing Kerr nonlinearities. The intensity profiles of the novel waves are identical with those of fundamental bright or dark spatial solitons supported by homogeneous passive waveguides with the same type of nonlinearity. Thus, we reveal a previously unnoticed connection between spatial solitons and self-similar waves. We also suggest that the discovered self-similar waves can be used in a promising scheme for the amplification and focusing of spatial solitons in future all-optical networks.

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PubMed2004

Asymmetric incoherent vector solitons.

We introduce a wide class of partially coherent, partially polarized solitons whose second-order statistical properties include a certain type of reflectional symmetry to be referred to as the specularity. We describe generic properties of such solitons in any noninstantaneous saturable nonlinear media. We derive closed form analytical expressions for the intensity profiles as well as the degree of polarization of specular and antispecular partially coherent solitons supported by logarithmically saturable nonlinear media.

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PubMed2003

Partially coherent vortex beams with a separable phase.

We propose and experimentally implement a method for the generation of a wide class of partially spatially coherent vortex beams whose cross-spectral density has a separable functional form in polar coordinates. We study phase singularities of the spectral degree of coherence of the new beams.

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PubMed2002

Linear superposition principle for partially coherent solitons.

The existence of a linear superposition principle is demonstrated for partially coherent solitons with identical intensity profiles that are supported by the same medium. Since such degenerate partially coherent solitons are generic for saturable as well as for Kerr-like nonlinear media, our results are relevant to any non-instantaneous nonlinear media. The proposed superposition principle suggests a physical interpretation of partially coherent solitons as generalized linear modes of their self-induced waveguides. The power of such a superposition principle is illustrated by identifying soliton structures with controllable coherence properties both in logarithmically saturable and in Kerr-like nonlinear media.

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PubMed2001

Universal structure of field correlations within a fluctuating medium.

We study the structure of the second-order correlation function of scalar wave fields, which are generated by statistically stationary sources, fluctuating within a homogeneous dissipative medium. We derive a closed-form analytical expression for the spectral degree of coherence of the wave field. If the dissipation in the medium is sufficiently small, and the source fluctuations are statistically isotropic, the degree of spatial coherence of the field produced by any such source is shown to be proportional to the imaginary part of the Green's function of the system, with a proportionality factor depending on the dimensionality of the field. The result holds for wave fields in both three and two spatial dimensions, but not in one dimension. We discuss the physical nature of such universal forms of the spectral degree of coherence.

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