Exceptional points in a passive strip waveguide
Exceptional points (EPs) in non-Hermitian systems have attracted significant interest due to their unique behaviors, including novel wave propagation and radiation. While EPs have been explored in various photonic systems, their integration into standard photonic platforms can expand their applicabi...
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| Format: | Article |
| Language: | English |
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De Gruyter
2025-03-01
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| Series: | Nanophotonics |
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| Online Access: | https://doi.org/10.1515/nanoph-2024-0701 |
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| _version_ | 1849310620108718080 |
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| author | Hasanli Shamkhal Hasan Mehedi Yoon Hyejin Lee Seungyong Kim Sangsik |
| author_facet | Hasanli Shamkhal Hasan Mehedi Yoon Hyejin Lee Seungyong Kim Sangsik |
| author_sort | Hasanli Shamkhal |
| collection | DOAJ |
| description | Exceptional points (EPs) in non-Hermitian systems have attracted significant interest due to their unique behaviors, including novel wave propagation and radiation. While EPs have been explored in various photonic systems, their integration into standard photonic platforms can expand their applicability to broader technological domains. In this work, we propose and experimentally demonstrate EPs in an integrated photonic strip waveguide configuration, exhibiting unique deep wave penetration and uniform-intensity radiation profiles. By introducing the second-order grating on one side of the waveguide, forward and backward propagating modes are coupled both directly through second-order coupling and indirectly through first-order coupling via a radiative intermediate mode. To describe the EP behavior in a strip configuration, we introduce modified coupled-mode equations that account for both transverse and longitudinal components. These coupled-mode formulas reveal the formation of EPs in bandgap closure, achieved by numerically optimizing the grating’s duty cycle to manipulate the first- and second-order couplings simultaneously. Experimental observations, consistent with simulations, confirm the EP behavior, with symmetric transmission spectra and constant radiation profiles at the EP wavelength, in contrast to conventional exponential decay observed at detuned wavelengths. These results demonstrate the realization of EPs in a widely applicable strip waveguide configuration, paving the way for advanced EP applications in nonlinear and ultrafast photonics, as well as advanced sensing technologies. |
| format | Article |
| id | doaj-art-ea352af2ab864e07a6db41d3daae78a3 |
| institution | Kabale University |
| issn | 2192-8614 |
| language | English |
| publishDate | 2025-03-01 |
| publisher | De Gruyter |
| record_format | Article |
| series | Nanophotonics |
| spelling | doaj-art-ea352af2ab864e07a6db41d3daae78a32025-08-20T03:53:41ZengDe GruyterNanophotonics2192-86142025-03-011481301130910.1515/nanoph-2024-0701Exceptional points in a passive strip waveguideHasanli Shamkhal0Hasan Mehedi1Yoon Hyejin2Lee Seungyong3Kim Sangsik4School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of KoreaDepartment of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX79409, USAGraduate School of Quantum Science and Technology, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of KoreaSchool of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of KoreaSchool of Electrical Engineering and Graduate School of Quantum Science and Technology, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of KoreaExceptional points (EPs) in non-Hermitian systems have attracted significant interest due to their unique behaviors, including novel wave propagation and radiation. While EPs have been explored in various photonic systems, their integration into standard photonic platforms can expand their applicability to broader technological domains. In this work, we propose and experimentally demonstrate EPs in an integrated photonic strip waveguide configuration, exhibiting unique deep wave penetration and uniform-intensity radiation profiles. By introducing the second-order grating on one side of the waveguide, forward and backward propagating modes are coupled both directly through second-order coupling and indirectly through first-order coupling via a radiative intermediate mode. To describe the EP behavior in a strip configuration, we introduce modified coupled-mode equations that account for both transverse and longitudinal components. These coupled-mode formulas reveal the formation of EPs in bandgap closure, achieved by numerically optimizing the grating’s duty cycle to manipulate the first- and second-order couplings simultaneously. Experimental observations, consistent with simulations, confirm the EP behavior, with symmetric transmission spectra and constant radiation profiles at the EP wavelength, in contrast to conventional exponential decay observed at detuned wavelengths. These results demonstrate the realization of EPs in a widely applicable strip waveguide configuration, paving the way for advanced EP applications in nonlinear and ultrafast photonics, as well as advanced sensing technologies.https://doi.org/10.1515/nanoph-2024-0701exceptional pointswaveguidephotonic integrated circuitnon-hermitian photonics |
| spellingShingle | Hasanli Shamkhal Hasan Mehedi Yoon Hyejin Lee Seungyong Kim Sangsik Exceptional points in a passive strip waveguide Nanophotonics exceptional points waveguide photonic integrated circuit non-hermitian photonics |
| title | Exceptional points in a passive strip waveguide |
| title_full | Exceptional points in a passive strip waveguide |
| title_fullStr | Exceptional points in a passive strip waveguide |
| title_full_unstemmed | Exceptional points in a passive strip waveguide |
| title_short | Exceptional points in a passive strip waveguide |
| title_sort | exceptional points in a passive strip waveguide |
| topic | exceptional points waveguide photonic integrated circuit non-hermitian photonics |
| url | https://doi.org/10.1515/nanoph-2024-0701 |
| work_keys_str_mv | AT hasanlishamkhal exceptionalpointsinapassivestripwaveguide AT hasanmehedi exceptionalpointsinapassivestripwaveguide AT yoonhyejin exceptionalpointsinapassivestripwaveguide AT leeseungyong exceptionalpointsinapassivestripwaveguide AT kimsangsik exceptionalpointsinapassivestripwaveguide |