Abstract Eigenstate coalescence in non-Hermitian systems is widely observed diverse scientific domains encompassing optics and open quantum systems. Recent investigations have revealed that adiabatic encircling of exceptional points (EPs) leads to a nontrivial Berry phase addition an exchange eigenstates. Based on these phenomena, we propose this work exhaustive classification framework for EPs physical In contrast previous classifications only incorporate the eigenstate effect, our proposed...

We investigate lasing characteristics of a Limaçon-shaped InGaAsP semiconductor microcavity laser. When the cavity is pumped with dc current, laser generates directional emissions. Near threshold series modes equidistantly spaced resonant frequencies emit. From mode spacing we confirm emission whispering gallery-type resonance modes. As injection current increases, single becomes dominant emission. The quality factor obtained near threshold, which larger than 22 000.

One of the interesting features open quantum and wave systems is non-Hermitian degeneracy called an exceptional point, where not only energy levels but also corresponding eigenstates coalesce. We demonstrate that such a can appear in optical microdisk cavities by deforming boundary extremely weakly. This surprising finding explained semiclassical theory dynamical tunneling. It shown points come nearly degenerated pairs, originating from different symmetry classes modes. A spatially local...

The moiré superlattice of misaligned atomic bilayers paves the way for designing a new class materials with wide tunability. In this work, we propose photonic analog based on dielectric resonator quasi-atoms. sharp contrast to van der Waals weak interlayer coupling, realize strong coupling regime in superlattice, characterized by cascades robust flat bands at large twist-angles. Surprisingly, find that these are non-trivial band topology, origin which is pattern arrangement. physical...

We explore the decay rates of optical modes in asymmetric microcavities with mixed phase space across a wide range wavelengths that extend deep into semiclassical, i.e., short-wavelength limit. Implementing an efficient numerical method, we computed 1000000 eigenmodes and discovered certain form sequential separate branches increasing wavenumber eventually merge smooth curves. The analysis localization properties Husimi distributions reveals each branch corresponds to periodic orbit closed...

Unpinned Dirac points (DPs) are nodal point degeneracies that occur at generic momentum lacking high symmetry, often exhibiting characteristics typically forbidden by symmetry. While this phenomenon has been observed in solid-state materials, the formation of unpinned DPs photonic crystals not extensively studied. This study presents a novel approach to achieving two-dimensional ``defected crystals"-photonic superlattices created modifying size or refractive index dielectric disks specific...

A striking signature of the non-Hermitian physics in open systems is existence exceptional points (EPs) parameter space. In contrast to a conventional degeneracy, an EP involves not only coalescence eigenvalues but simultaneously that corresponding eigenstates as well. Here, we study EPs optical microdisk cavities with concentrically layered refractive index profile. For double-layered cavity show two coalescing modes. triple-layered verify and discuss emergence involving three modes single cavity.

Fermi resonance is a phenomenon of quantum mechanical superposition, which most often occurs between normal and overtone modes in molecular systems that are nearly coincident energy. We find scarred resonances deformed dielectric microcavities the very resonance, is, pair quasinormal interact with each other due to coupling generated through an avoided crossing. Then number difference modes, consequence equals periodic orbits, whereby localized on orbits. derive relation orbits confirm it...

Recently, it has been shown numerically and by a semiclassical approach [Phys. Rev. Lett. 120, 093902 (2018)] that second-order exceptional points can appear in the spectrum of weakly deformed microdisk resonators coupling optical modes with different angular momentum. Here, we use perturbation theory for weak boundary deformations to derive an effective non-Hermitian Hamiltonian from which obtain analytical formulas describe formation such systems. The is extended third-order confirmed full...

Open quantum and wave systems can exhibit non-Hermitian degeneracies called exceptional points, where both the eigenvalues corresponding eigenstates coalesce. Previously, such points have been investigated in dielectric microcavities terms of optical modes which are well confined inside cavity. However, beside these so-called “internal modes” with a relatively high quality factor, there exists another kind mode “external modes,” large decay rate almost zero intensity In present paper, we...

A large number of different types second-order non-Hermitian degeneracies called exceptional points (EPs) were found in various physical systems depending on the mechanism coupling between eigenstates. We show that these EPs can be hybridized to form higher-order EPs, which preserve original properties initial before hybridization. For a demonstration, we hybridize chiral and supermode where former latter are results intra-disk inter-disk mode an optical system comprised two Mie-scale...

In an elliptic In${}_{x}$Ga${}_{1\ensuremath{-}x}$AsP microcavity laser, various scarlike modes are experimentally observed. Below the lasing threshold, a bouncing-ball, triangle, double, and triple bow-tie mode spontaneously emit. Above lases alone. Our numerical analysis reveals that is not caused by regular islands in phase space due to Goos-H\"anchen shift, but unstable periodic orbits light emission assisted quasiperiodic orbit.

We investigate the impact of local dynamics on chaos-assisted tunneling in a highly deformed microcavity whose classical ray exhibits small measure trapezoidal-shaped orbit (TSO) stability islands main chaotic sea. These two classically completely decomposed regions phase space can support resonance modes their own respectively. Using numerical and wave analyses, we show that emission characteristics TSO mode are determined by near islands. The other high-Q modes, hand, governed usual...

It was reported that Q spoiling in a chaotic microcavity is caused by chaos [PRL, 75, 2682 (1995)] and chaos-assisted tunneling [Nature 385, 45 (1997)]. However, even when cavity slightly deformed not to exhibit broad region phase space, high modes are spoiled. We find this the transition of whispering gallery mode (WGM) scarred resonance WGM interacts with its pair quasi-normal through an avoided crossing. prove induces quadrupole dielectric showing factors obtained from Husimi functions...

Chirality of a resonance localized on an islands chain is studied in deformed Reuleaux triangular-shaped microcavity, where clockwise and counter traveling rays are classically separated. A period-5 exhibits chiral emission due to the asymmetric cavity shape. experimentally proved InGaAsP multi-quantum-well semiconductor laser by showing that experimental characteristics well coincide with wave dynamical ones.

We report a new type of dynamical tunneling, which is mediated by resonant torus, i.e., nonisolated periodic orbit. To elucidate the phenomenon, we take an open elliptic cavity and show that pair resonances localized on two classically disconnected tori tunnel through torus when they interact with each other. This so-called torus-assisted tunneling verified using Husimi functions, corresponding actions, function distributions, standard deviations actions.

We study the frequency splitting of nearly degenerate optical modes in weakly deformed microdisks. The analysis is restricted to even- and odd-parity cavities with a mirror-reflection symmetry. explained semiclassical approach by dynamical tunneling (resonance-assisted tunneling) between clockwise- counterclockwise-propagating waves. derive predictions for splittings which are good agreement full numerical calculations. Two deformations studied detail, ellipse quadrupole, representing...

We elucidate that Fermi resonance ever plays a decisive role in dynamical tunneling chaotic billiard. Interacting with each other through an avoided crossing, pair of eigenfunctions are coupled channels for tunneling. In this case, the islands chain and its unstable periodic orbit, which equals quantum number difference eigenfunctions. This phenomenon is confirmed quadrupole billiard relation resonance.

A formation of second-order non-Hermitian degeneracies, called exceptional points (EPs), in a chaotic oval-shaped dielectric microdisk is studied. Different symmetric optical modes localized on stable period-3 orbit coalesce to form chiral EPs. Unlike circular perturbed by two scatterers (CTS), our proposed system requires only one scatterer build The positions for counterpropagating EP are far distant from another and almost steady against varying sizes contrast the CTS case. Our results...

We study a systematic formation of continuous exceptional points (EPs) in fully-asymmetric optical microdisk. A parametric generation chiral EP modes is investigated by analyzing asymmetricity-dependent coupling elements an effective Hamiltonian. It shown that given the external perturbation, frequency splitting around EPs scaled fundamental "strength" [J. Wiersig, Phys. Rev. Res.4, 023121 (2022)10.1103/PhysRevResearch.4.023121] multiplied extra responding strength newly added perturbation....

We report directional single mode emission in an InGaAsP semiconductor microcavity laser, which is composed of a circle and isosceles trapezoid. When exciting whole cavity, the laser generates without hopping two directions over wide range continuous injection currents. In spectrum, it confirmed from equidistant spacing that scar becomes lasing above threshold. A numerical analysis boundary element method shows far-field pattern resonance agrees well with experiment.

In an elliptic billiard, we find avoided level crossings taking place over wide ranges, which are of a Demkov type for generations eigenfunctions localized on islands chain and its pair unstable periodic orbit. For proof the existence crossings, first, show that quantized eigenvalue orbit, obtained by Einstein-Brillouin-Keller quantization rule, passes eigenvalues bouncing-ball modes orbit after so pairs sequentially generated. Next, using perturbed Hamiltonian, off-diagonal elements in...

We find unidirectional emission in a cardioid-shaped microcavity laser. When deformation parameter is well adjusted, rays starting around period-5 unstable periodic orbit emit unidirectionally. To confirm the direction, we fabricate laser by using an InGaAsP semiconductor and investigate characteristics. excited current injection with dc current, resonances localized on