https://scholar.dgist.ac.kr/handle/20.500.11750/794 Sat, 04 Apr 2026 20:53:43 GMT 2026-04-04T20:53:43Z https://scholar.dgist.ac.kr/handle/20.500.11750/60115 Title: Incomplete chirality of exceptional points in asymmetric optical microcavity Author(s): Kim, Hyundong; Eom, Youngmin; Lee, Hoyeon; Cho, Yanni; Lee, Seungwoo; Gwak, Sunjae; Yu, Hyeon-Hye; Yi, Chang-Hwan; Kim, Chil-Min Abstract: A chiral exceptional point (EP) in an optical microcavity emerges from the coalescence of even and odd modes with identical azimuthal modal numbers under asymmetric perturbation. While the chirality of such EPs is well understood in circular disks with asymmetrically positioned Rayleigh scatterers, it becomes more intricate in asymmetric microcavities, where the contributing modes can exhibit nontrivial wave morphology according to chaotic deformation. To explore this, we consider a stand-alone microcavity composed of one half ellipse and two quarter ellipses, for which EPs exhibit incomplete chirality. Our analysis reveals that this incomplete chirality originates from prior mode coupling. After the prior mode coupling, only the quasinormal modes within each superposed mode pair that have identical azimuthal modal numbers but opposite parities contribute to the chirality at EPs. Consequently, the chirality of the EP modes remains incomplete, depending on the relative weight of the original mode pair. Finally, we analyze the formation of EPs and their chiral properties in a generic asymmetric microcavity, providing insights into the underlying mechanisms of incomplete chirality. Tue, 30 Sep 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60115 2025-09-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/45978 Title: Maximization of a frequency splitting on continuous exceptional points in asymmetric optical microdisks Author(s): Kim, Hyundong; Gwak, Sunjae; Yu, Hyeon-Hye; Ryu, Jinhyeok; Kim, Chil-Min; YI, Chang-Hwan Abstract: We study a systematic formation of continuous exceptional points (EPs) in a fully-asymmetric optical microdisk. A parametric generation of chiral EP modes is investigated by analyzing asymmetricity-dependent coupling elements in an effective Hamiltonian. It is shown that given the external perturbation, the frequency splitting around EPs is scaled by the fundamental “strength” of EPs [J. Wiersig, Phys. Rev. Res. 4, 023121 (2022)] multiplied by the extra responding strength of the newly added perturbation. Our finding demonstrates that the sensitivity of EP-based sensors can be maximized by carefully examining the continuous formation of EPs. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement. Fri, 31 Mar 2023 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/45978 2023-03-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/17206 Title: Impact of non-Hermitian mode interaction on inter-cavity light transfer Author(s): Yu, Hyeon-Hye; Gwak, Sunjae; Ryu, Jinhyeok; Kim, Hyundong; Kim, Ji-Hwan; Ryu, Jung-Wan; Kim, Chil-Min; Yi, Chang-Hwan Abstract: Understanding inter-site mutual mode interaction in coupled physical systems is essential to comprehend large compound systems, as this local interaction determines the successive multiple inter-site energy transfer efficiencies. In the present study, we demonstrate that only the non-Hermitian coupling can correctly account for the light transfer between two coupled optical cavities. We also reveal that the non-Hermitian coupling effect becomes crucial as the system dimension decreases. Our results provide important insight for handling general-coupled devices in the subwavelength regime. (C) 2022 Chinese Laser Press Sat, 30 Apr 2022 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/17206 2022-04-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/17205 Title: Far-Field Correlations Verifying Non-Hermitian Degeneracy of Optical Modes Author(s): Gwak, S.; Ryu, J.; Kim, H.; Yu, H.-H.; Kim, C.-M.; Yi, C.-H. Abstract: An experimental verification of an exceptional point (EP) in a stand-alone chaotic microcavity is a tough issue because as deformation parameters are fixed the traditional frequency analysis methods cannot be applied any more. Through numerical investigations with an asymmetric Reuleaux triangle microcavity (ARTM), we find that the eigenvalue difference of paired modes can approach near-zero regardless of nonorthogonality of the modes. In this case, for a definite verification of EPs in experiments, wave function coalescence should be confirmed. For this, we suggest the method of exploiting correlation of far-field patterns (FFPs), which is directly related to spatial mode patterns. In an ARTM, we demonstrate that the FFP correlation of paired modes can be used to confirm wave function coalescence when an eigenvalue difference approaches near zero. Sun, 31 Jul 2022 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/17205 2022-07-31T15:00:00Z