Category Institute of Spectroscopy – Russian Academy of Sciences

Entries 2 Total

Unbreakable PT-symmetry of solitons supported by inhomogeneous defocusing nonlinearity

Aug 27, ’14 8:59 PM

Yaroslav V. Kartashov, Boris A. Malomed, Lluis Torner

We consider bright solitons supported by a symmetric inhomogeneous defocusing nonlinearity growing rapidly enough toward the periphery of the medium, combined with an antisymmetric gain-loss profile. Despite the absence of any symmetric modulation of the linear refractive index, which is usually required to establish a PT-symmetry in the form of a purely real spectrum of modes, we show that the PT-symmetry is never broken in the present system, and that the system always supports stable bright solitons, fundamental and multi-pole ones. Such phenomenon is connected to non-linearizability of the underlying evolution equation. The increase of the gain-losses strength results, in lieu of the PT-symmetry breaking, in merger of pairs of different soliton branches, such as fundamental and dipole, or tripole and quadrupole ones. The fundamental and dipole solitons remain stable for all values of the gain-loss coefficient.

http://arxiv.org/abs/1408.6174
Optics (physics.optics); Pattern Formation and Solitons (nlin.PS)

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PT-symmetry in optics beyond the paraxial approximation

Aug 13, ’14 8:51 PM

Changming Huang, Fangwei Ye, Yaroslav V. Kartashov, Boris A Malomed, Xianfeng Chen

The concept of the PT-symmetry, originating from the quantum field theory, has been intensively investigated in optics, stimulated by the similarity between the Schr\”odinger equation and the paraxial wave equation that governs the propagation of light in a guiding structure. We go beyond the bounds of the paraxial approximation and demonstrate, using the solution of the Maxwell’s equations for light beams propagating in deeply subwavelength waveguides and periodic lattices with “balanced” gain and loss, that the PT symmetry may stay unbroken in this setting. Moreover, the PT-symmetry in subwavelength optical structures may be restored after being initially broken upon the increase of gain and loss. Critical gain/loss levels, at which the breakup and subsequent restoration of the PT symmetry occur, strongly depend on the scale of the structure.

http://arxiv.org/abs/1408.2630
Optics (physics.optics); Pattern Formation and Solitons (nlin.PS)

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