arXiv subjects

Ioannis Kiorpelidis

Publications and source records attributed to Ioannis Kiorpelidis.

5 recordsLinked to original sources

arXiv2026

Optical Tautochrone and Squeezing Dynamics in Nonuniform Lattices

We present exact analogies between the tautochrone problem of classical mechanics and the squeezed states of quantum optics to optical lattices. Both phenomena emerge in the same physical system, that of waveguide arrays with nonuniform couplings. Extension to two dimensions yields Lissajous-type trajectories and multidirectional tautochrone focusing. Furthermore, we investigate the impact of Kerr nonlinearity and show that it determines the diffraction behavior, namely coherent-state-like or squeezed propagation. These quantum inspired classical lattices highlight the role of the coupling coefficients to beam engineering and light control in complex media.

physics.optics↗

arXiv2025

Scaling of pseudospectra in exponentially sensitive lattices

One of the important features of non-Hermitian Hamiltonians is the existence of a unique type of singularities, the so-called exceptional points (EPs). When the corresponding systems operate around such singularities, they exhibit ultrasensitive behavior that has no analog in conservative systems. An alternative way to realize such ultra-sensitivity relies on asymmetric couplings. Here we provide a comprehensive analysis based on pseudospectra, that shows the origin of exponential sensitivity, without relying on topological zero modes or the localization of all eigenstates (skin effect), but on the underlying extreme lattice non-normality. In particular, we consider four different types of lattices (Hatano-Nelson, Sylvester-Kac, non-Hermitian Su-Schrieffer-Heeger and a non-Hermitian random lattice) and identify the conditions for exponential sensitivity as a function of the lattice size. Complex and structured pseudospectra reveal the signatures of exponential sensitivity both on the eigenvalue spectra and on the underlying dynamics. Our study, may open new directions on studies related to the exploitation of non-normality for constructing ultra-sensitive systems that do not rely on the existence of EPs.

physics.optics↗

arXiv2025

Robustness of perfect transmission resonances to asymmetric perturbation

We investigate the impact of asymmetric perturbations on the perfect transmission resonances (PTRs) of one-dimensional finite periodic systems. With no perturbations, the scattering region consists of $N$ identical cells, and the transmission spectrum exhibits at least $N-1$ PTRs in each pass band of the Bloch dispersion of the unit cell. By introducing a perturbation, the periodic structure is broken, which \textit{a priori} results in the elimination of all PTRs. However, we demonstrate that PTRs can still arise under asymmetric perturbations when the unperturbed system possesses mirror symmetry, utilizing the $\mathcal{PT}$ symmetry of the unperturbed reflectionless eigenvalue problem. We also reveal an intriguing connection between two seemingly independent PTRs that lies in the symmetry of the unperturbed unit cell: If one PTR is preserved, then a dual one is necessarily also preserved. Our findings offer insights for the design of, for example, a robust antireflection setup at multiple wavelengths or all-optical diode devices.

quant-ph↗

arXiv2024

Transient amplification in stable Floquet media

The Mathieu equation occurs naturally in the description of vibrations or in the propagation of waves in media with time-periodic refractive index. It is known to lead to exponential parametric instability in some regions of the parameter space. However, even in the stable region the matrix that propagates the initial conditions forward in time is non-normal and therefore it can result in transient amplification. By optimizing over initial conditions as well as initial time we show that significant transient amplifications can be obtained, going beyond the one simply stemming from adiabatic invariance. Moreover, we explore the monodromy matrix in more depth, by studying its $ε$-pseudospectra and Petermann factors, demonstrating that is the degree of non-normality of this matrix that determines the global amplifying features. In the context of wave propagation in time-varying media, this transient behavior allows us to display arbitrary amplification of the wave amplitude that is not due to exponential parametric instability.

cond-mat.other↗

arXiv2021

Disorder-induced topological phase transition in a 1D mechanical system

We numerically investigate the topological phase transition induced purely by disorder in a spring-mass chain. We employ two types of disorders - chiral and random types - to explore the interplay between topology and disorder. By tracking the evolution of real space topological invariants, we obtain the topological phase diagrams and demonstrate the bilateral capacity of disorder to drive topological transitions, from topologically nontrivial to trivial and vice versa. The corresponding transition is accompanied by the realization of a mechanical Topological Anderson Insulator. The findings from this study hint that the combination of disorder and topology can serve as an efficient control knob to manipulate the transfer of mechanical energy.

physics.app-ph↗