Next-nearest-neighbor resonance coupling and exceptional singularities in degenerate optical microcavities
01 Oct 2017-Journal of The Optical Society of America B-optical Physics (Optical Society of America)-Vol. 34, Iss: 10, pp 2050-2058
TL;DR: In this article, the effect of interplay between the proposed resonance interactions and the incorporated non-Hermiticity in the microcavity is analyzed drawing a special attention to the existence of hidden singularities, namely exceptional points (EPs), where at least two coupled resonances coalesce.
Abstract: We report a specially configured open optical microcavity, imposing a spatially imbalanced gain–loss profile, to host an exclusively proposed next-nearest-neighbor resonance coupling scheme. Adopting the scattering matrix (S-matrix) formalism, the effect of interplay between such proposed resonance interactions and the incorporated non-Hermiticity in the microcavity is analyzed drawing a special attention to the existence of hidden singularities, namely exceptional points (EPs), where at least two coupled resonances coalesce. We establish adiabatic flip-of-state phenomenon of the coupled resonances in the complex frequency plane (k-plane), which is essentially an outcome of the fact that the respective EP is being encircled in the system parameter plane. Encountering such multiple EPs, the robustness of flip-of-states phenomena has been analyzed via continuous tuning of coupling parameters along a special hidden singular line which connects all the EPs in the cavity. Such a numerically devised cavity, incorporating the exclusive next neighbor coupling scheme, has been designed for the first time to study the unconventional optical phenomena in the vicinity of EPs.
Citations
More filters
TL;DR: In this paper, the dynamical encirclement of non-Hermitian EPs has been studied in a non-hermitian system with state-flipping and peculiar phase accumulation features.
Abstract: Exceptional points (EPs) in non-Hermitian systems have recently attracted considerable attention owing to unique state-flipping and peculiar phase accumulation features. The dynamical encirclement ...
35 citations
TL;DR: In this paper, the authors studied the simultaneous interactions between three successive coupled states via avoided-resonance-crossing (ARC) phenomena, and identified two EP2s near two ARC regimes.
Abstract: One of the most intriguing topological features of open systems is that they exhibit exceptional point (EP) singularities. Apart from the widely explored second-order EPs (EP2s), the exploration of higher-order EPs in any system requires more complex topology, which is still a challenge. Here, we encounter a third-order EP (EP3) with the simultaneous presence of multiple second-order EPs in a simple fabrication feasible gain-loss assisted trilayer optical microcavity. Using the scattering-matrix formalism, we study the simultaneous interactions between three successive coupled states via avoided-resonance-crossing (ARC) phenomena, and we identify two EP2s near two ARC regimes. Such an occurrence of two EP2s inside a closed two-dimensional parametric space associated with an unbalanced gain-loss profile leads to the functionality of a cube-root branch point, i.e., an EP3. Following an adiabatic variation of two control parameters around the embedded EP3 in the presence of two identified EP2s, we present a robust successive-state-conversion mechanism among three coupled states. The proposed scheme indeed opens up a unique platform to manipulate light in integrated photonic devices.
20 citations
Cites background from "Next-nearest-neighbor resonance cou..."
...[16] A....
[...]
...Such unique topological features of EPs have been exploited in-depth to meet a wide range of technological challenges like, asymmetric-mode-conversion [10–14], topological state-switching [15–17], lasing-control [18], unidirectional propagation with enhanced nonreciprocity [19, 20], sensitivity enhancement [21–23], etc....
[...]
TL;DR: In this paper, an all-lossy dual-mode planar waveguide structure is proposed for topological control of light signals, where the topological properties of an EP are achieved by patterning the longitudinal loss profile only.
Abstract: Recent technological advances have boosted research related to $e\phantom{\rule{0}{0ex}}x\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ $p\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}s$ (EPs), singularities arising in non-Hermitian quantum mechanics that once seemed purely mathematical. Device-level implementation of EPs has been primarily in gain-loss-balanced toroidal optical microcavities, but too much gain can cause such a system to become unstable. This study proposes an all-lossy dual-mode planar waveguide structure, in which the topological properties of an EP are achieved by patterning the longitudinal loss profile only. This scheme needs no active pumping, is accessible to many conventional optical elements, and offers a platform for topological control of light signals.
16 citations
TL;DR: In this paper, a 1D planar optical waveguide with transverse distribution of inhomogeneous loss profile, which exhibits an exceptional point (EP), is presented, where the interaction between them in the vicinity of the EP is controlled by proper adjustment of the inhomogeneity in attenuation profile only.
Abstract: We report a 1D planar optical waveguide with transverse distribution of inhomogeneous loss profile, which exhibits an exceptional point (EP). The waveguide hosts two leaky resonant modes; where the interaction between them in the vicinity of the EP is controlled by proper adjustment of the inhomogeneity in attenuation profile only. We study the adiabatic dynamics of propagation constants of the coupled modes by quasi-static encirclement of control parameters around the EP. Realizing such an encirclement with the inhomogeneous loss distribution along the direction of light propagation, we report the breakdown of adiabatic evolution of two coupled modes through the waveguide in presence of an EP. Here, during conversion the output mode is irrespective of the choice of input excited mode but depends on the direction of light transportation. This topologically controlled, robust scheme of asymmetric mode conversion in the platform of the proposed all-lossy waveguide structure may open up an extensive way-out for implementation of state-transfer applications in chirality driven waveguide-based devices.
14 citations
References
More filters
TL;DR: It is demonstrated that a dynamical encircling of an exceptional point is analogous to the scattering through a two-mode waveguide with suitably designed boundaries and losses, and mode transitions are induced that transform this device into a robust and asymmetric switch between different waveguide modes.
Abstract: Physical systems with loss or gain have resonant modes that decay or grow exponentially with time. Whenever two such modes coalesce both in their resonant frequency and their rate of decay or growth, an 'exceptional point' occurs, giving rise to fascinating phenomena that defy our physical intuition. Particularly intriguing behaviour is predicted to appear when an exceptional point is encircled sufficiently slowly, such as a state-flip or the accumulation of a geometric phase. The topological structure of exceptional points has been experimentally explored, but a full dynamical encircling of such a point and the associated breakdown of adiabaticity have remained out of reach of measurement. Here we demonstrate that a dynamical encircling of an exceptional point is analogous to the scattering through a two-mode waveguide with suitably designed boundaries and losses. We present experimental results from a corresponding waveguide structure that steers incoming waves around an exceptional point during the transmission process. In this way, mode transitions are induced that transform this device into a robust and asymmetric switch between different waveguide modes. This work will enable the exploration of exceptional point physics in system control and state transfer schemes at the crossroads between fundamental research and practical applications.
776 citations
TL;DR: So-called exceptional points, degenerate quantum states, allow higher energy splitting under the same perturbation conditions, greatly improving the detection sensitivity of sensors as mentioned in this paper, and thus improving the performance of sensors.
Abstract: So-called exceptional points, degenerate quantum states, allow higher energy splitting under the same perturbation conditions, greatly improving the detection sensitivity of sensors.
708 citations
TL;DR: A microwave cavity experiment where exceptional points (EPs), which are square root singularities of the eigenvalues as function of a complex interaction parameter, are encircled in the laboratory and one of the Eigenvectors undergoes a sign change which can be discerned in the field patterns.
Abstract: We report on a microwave cavity experiment where exceptional points (EPs), which are square root singularities of the eigenvalues as function of a complex interaction parameter, are encircled in the laboratory. The real and imaginary parts of an eigenvalue are given by the frequency and width of a resonance and the eigenvectors by the field distributions. Repulsion of eigenvalues--always associated with EPs--implies frequency anticrossing (crossing) whenever width crossing (anticrossing) is present. The eigenvalues and eigenvectors are interchanged while encircling an EP, but one of the eigenvectors undergoes a sign change which can be discerned in the field patterns.
628 citations
TL;DR: In this article, a physical realization of scattering by -symmetric potentials is provided, for an electromagnetic wave travelling along a planar slab waveguide filled with gain and absorbing media in contiguous regions.
Abstract: A physical realization of scattering by -symmetric potentials is provided: we show that the Maxwell equations, for an electromagnetic wave travelling along a planar slab waveguide filled with gain and absorbing media in contiguous regions, can be approximated in a parameter range by a Schrodinger equation with a -symmetric scattering potential.
459 citations
TL;DR: In this paper, a general theory of sensors based on the detection of splittings of resonant frequencies or energy levels operating at so-called exceptional points is presented, where the complex-square-root topology near such non-Hermitian degeneracies has a great potential for enhanced sensitivity.
Abstract: A general theory of sensors based on the detection of splittings of resonant frequencies or energy levels operating at so-called exceptional points is presented. Exploiting the complex-square-root topology near such non-Hermitian degeneracies has a great potential for enhanced sensitivity. Passive and active systems are discussed. The theory is specified for whispering-gallery microcavity sensors for particle detection. As example, a microdisk with two holes is studied numerically. The theory and numerical simulations demonstrate a sevenfold enhancement of the sensitivity.
327 citations