arXiv subjects

Khalil Sabour

Publications and source records attributed to Khalil Sabour.

4 recordsLinked to original sources

arXiv2026

Thresholdless corner vortex solitons in fractal Sierpi\'nski topological insulators

Quantized vortices are ubiquitous in physics, spanning superconductivity, astrophysics, superfluid condensed matter systems, and nonlinear optics. Yet embedding vorticity into topologically protected nonlinear states has remained a major challenge, with all previously observed corner solitons in higher-order topological insulators (HOTIs) exhibiting only trivial phase distributions. Here, we report on the first realization of stable topological corner vortex solitons in a photonic fractal HOTI. Using an array of laser-written waveguides in the shape of Sierpi\'nski gasket with a controllable distortion, we design linear topological vortex modes, from which nonlinear corner vortex solitons bifurcate. Moreover, we demonstrate that these solitons exhibit exceptional robustness across a broad power range and, unlike vortex solitons in topologically trivial lattices, form without a power threshold. Our results introduce the angular momentum degree of freedom into the physics of topological corner modes, opening prospects for topologically protected vortex-based photonics.

physics.optics↗

arXiv2026

Polariton Topological Insulators with Disclinations

We introduce polariton topological insulator on aperiodic array of microcavity pillars with disclination. This unique dissipative and nonlinear topological system can have discrete rotational symmetry not achievable in structures constructed on periodic arrays that qualitatively affects the structure of topological modes. In such system resonant optical pump can be used for selective excitation of topological states forming on the disclination core in the center, while imposing vorticity on the pump profile allows to excite not only the simplest disclination states, but also vortex-carrying disclination states. Strong repulsive nonlinearity of polaritonic system leads to increasing with pump amplitude tilt of the resonance curves and bistability, with rich possibilities for control of shapes of nonlinear disclination states within topological gap by pump frequency detuning. Stability analysis predicts remarkable robustness of both vortex-free and vortex-carrying nonlinear disclination states in this system. We show that when topological charge of the pump exceeds maximal allowed charge in the disclination array with a given discrete rotational symmetry, the stationary states form that contain vortex clusters in their phase distributions. Our results extend the concept of topo-logical insulators with disclinations to the realm of nonlinear resonantly driven systems and show that rich bistability effects in them can be observed even for excited vortex-carrying topological states with different topological charges allowed by discrete rotational symmetry of the system.

physics.optics↗

arXiv2025

Fractal Polariton Topological Insulator

We introduce higher order polariton topological insulator (HOTI) realized with fractal array of microcavity pillars arranged into Sierpinski gasket-like geometry. This system exhibiting self similarity in different generations, can support localized modes either in the external or multiple internal corners depending on the controllable distortion introduced into first generation structure. Nonlinear corner modes can be selectively excited in this dissipative system using resonant optical pumping. Strong polariton-polariton interactions lead to tilt of the resonance curves and bistability as the pump amplitude increases, allowing control over corner state profiles. Linear stability analysis illustrates dynamical stability of such states. Our results show how nontrivial topology manifests itself in self similar, aperiodic structures and indicate that fractal geometry may bring qualitatively new localization scenarios in polariton HOTIs.

physics.optics↗

arXiv2024

Topological solitons in coupled Su-Schrieffer-Heeger waveguide arrays

We investigate the formation of multipole topological solitons at the edges of two and three coupled parallel Su-Schrieffer-Heeger (SSH) waveguide arrays. We show that independent variations of waveguide spacing in the unit cells (dimers) in coupled waveguide arrays result in the emergence at their edges of several topological edge states with different internal symmetry. The number of emerging edge states is determined by how many arrays are in topologically nontrivial phase. In the presence of nonlinearity, such edge states give rise to families of multipole topological edge solitons with distinct stability properties. Our results illustrate that coupling between quasi-one-dimensional topological structures substantially enriches the variety of stable topological edge solitons existing in them.

physics.optics↗