Next-nearest-neighbor resonance coupling and exceptional singularities in degenerate optical microcavities

Abstract

We report a specially configured non-Hermitian optical microcavity, imposing spatially imbalanced gain-loss profile, to host an exclusively proposed next nearest neighbor resonances coupling scheme. Adopting 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 (EP s); where at least two coupled resonances coalesce. We establish adiabatic flip-of-states phenomena 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 system parameter plane. Encountering such multiple EP s, the robustness of flip-of-states phenomena have been analyzed via continuous tuning of coupling parameters along a special hidden singular line which connects all the EP s in the cavity. Such a numerically devised cavity, incorporating the exclusive next neighbor coupling scheme, have been designed for the first time to study the unconventional optical phenomena in the vicinity of EP s.

Higher-order topological degeneracies and progress towards unique successive state switching in a four-level open system

“…In addition to EP4, we also explore the simultaneous existence of EP2s and EP3s in the same system and establish the possibility of the simultaneous existence of different orders of EPs in a particular system. Similar to 1D exceptional-line con-nects which connects multiple number of EP2s [20,21], we corroborate the relation of the perturbation parameters with the coupling control parameters, we formulate a 3D EP4region within which multiple locations that could be labeled as EP4 coexist. The chiral behavior of state-exchange around the E4 has also been established.…”

“…3(b). Such unconventional state-dynamics in the complex eigenvalue plane proves that the identified second-order singularity between E 1 and E 2 behaves as an EP2 [5,12,13,[20][21][22][23][24]. In Fig.…”

“…In presence of EPs, the exotic physical phenomena have been widely investigated in a wide range of open systems like atomic [12,13] and molecular [14] spectrum, microwave cavities [15], Bose-Einstein [16] and Bose-Hurburrd [17] systems, etc. Apart from these non-optical systems, the unconventional physical aspects of EPs have been mainly studied in various photonic systems like lasers [18,19], optical microcavities [20][21][22] and planar [23,24] and coupled [25][26][27] waveguides, photonic crystals [28,29], etc. Using optical gain-loss as nonconservative elements, such photonic sys- * somiit@rediffmail.com tems provide a leading platform to meet a wide range of contemporary technological applications like unidirectional light transmission [30], topological energy transfer [31], asymmetric mode switching/conversion [23][24][25][26], resonance scattering [32], cross-polarization mode coupling [29,33], lasing and antilasing [18,19], ultra-sensitive optical sensing [34][35][36][37], optical isolation with enhanced nonreciprocal effect [38,39], stopping of light [40] etc.…”

Third-order exceptional point and successive switching among three states in an optical microcavity

“…Now, during such encirclement, if we consider dynamical (i.e., time or length-scale dependent) parametric variation around an EP2, then the system behavior which follows the adiabaticity otherwise, breaks down yielding the chiral dynamics with timeasymmetric population transfer between the coupled states [9]. Such unique topological features of EPs have been exploited in-depth to meet a wide range of technological challenges like, asymmetric-mode-conversion [10][11][12][13][14], topological state-switching [15][16][17], lasing-control [18], unidirectional propagation with enhanced nonreciprocity [19,20], sensitivity enhancement [21][22][23], etc.…”

Exotic light dynamics around a fourth order exceptional point

“…The non-trivial topological behavior alongside different order of single or multiple EPs can be explored by an adiabatic encirclement process with a quasi-static variation of coupling parameters along a closed loop. Such an EP encirclement scheme results in the adiabatic permutation among the corresponding coupled states where they successively exchange their own identities [7,9,14,22,36,[38][39][40]. During such an EP-aided state-flipping, one of the eigenstates acquire an additional ±π phase at the end of the encirclement process [8,41].…”