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In non-Hermitian coulped-resonator networks, the eigenvectors of degenerate eigenmodes may become parallel due to the singularity at so-called Exceptional Points (EP). To exploit the parametric sensitivity at EPs, an important problem is,…

Quantum Physics · Physics 2019-01-31 Re-Bing Wu , Yu Zheng , Qi-Ming Chen , Yu-xi Liu

We present a transmission line theory of exceptional points of degeneracy (EPD) in coupled-mode guiding structures, i.e., a theory that illustrates the characteristics of coupled electromagnetic modes under a special dispersion degeneracy…

Optics · Physics 2017-09-15 Mohamed A. K. Othman , Filippo Capolino

Exceptional points (EPs) are remarkable spectral degeneracies in a non-Hermitian system's parameter space, where both eigenvalues and eigenstates coalesce. Here, we show that in non-Hermitian molecular chiral systems the position of EPs in…

Quantum Physics · Physics 2025-12-02 Nicola Mayer , Alexander Löhr , Nimrod Moiseyev , Misha Ivanov , Olga Smirnova

Modelocked frequency comb lasers have always operated with a single pulse circulating in the laser cavity. This meant that each laser technology had an associated limit on pulse repetition rate. Achieving higher rates required different…

Optics · Physics 2025-07-02 Kevin F. Lee , Jacob Lampen , Peng Li , Jie Jiang , Martin E. Fermann

Optical frequency combs are an essential tool for precision metrology experiments ranging in application from remote spectroscopic sensing of trace gases to the characterization and comparison of optical atomic clocks for precision…

We experimentally demonstrate and theoretically explain the onset of optical frequency combs in a simple cavity-enhanced second-harmonic-generation system, exploiting second-order nonlinear interactions. Two combs are simultaneously…

Exceptional points (EPs) are singularities of energy levels in non-Hermitian systems. In this Letter, we demonstrate the surface of EPs on a magnon polariton platform composed of coupled magnons and microwave photons. Our experiments show…

Mesoscale and Nanoscale Physics · Physics 2019-12-11 Xufeng Zhang , Kun Ding , Dafei Jin , Xianjing Zhou , Jing Xu

Optical frequency combs have the potential to improve the precision of the radial velocity measurement of celestial bodies, leading to breakthroughs in such fields as exoplanet exploration. For these purposes, the comb must have a broad…

Instrumentation and Methods for Astrophysics · Physics 2023-06-06 Keisuke Nakamura , Ken Kashiwagi , Sho Okubo , Hajime Inaba

Exceptional points (EP) are non-Hermitian spectral degeneracies where both eigenvalues and their corresponding eigenvectors coalesce. Recently, EPs have attracted a lot of attention as a means to enhance the responsivity of sensors, via the…

Applied Physics · Physics 2022-02-22 Rodion Kononchuk , Jizhe Cai , Fred Ellis , Ramathasan Thevamaran , Tsampikos Kottos

Exceptional points (EPs) are singular points on a parameter space at which some eigenvalues (scattering poles) and their corresponding eigenmodes coalesce. This study shows the existence of second- and third-order EPs in cylindrical elastic…

Classical Physics · Physics 2023-04-26 Kei Matsushima , Yuki Noguchi , Takayuki Yamada

We investigate the rich physics of photonic molecule lasers using a non-Hermitian dimer model. We show that several interesting features, predicted recently using a rigorous steady state ab-initio laser theory (SALT), can be captured by…

Optics · Physics 2015-06-19 Ramy El-Ganainy , Mercedeh Khajavikhan , Li Ge

Optical frequency comb devices have unlocked new capabilities in telecommunications, sensing, and metrology. Yet, precise in situ control of the comb spectral envelope remains extremely challenging. By introducing mode coupling with…

Exceptional points (EPs) represent non-Hermitian degeneracies where eigenvalues and eigenvectors coalesce, giving rise to enhanced sensitivity and critically damped dynamics. We demonstrate that when an EP coincides with a dissipative phase…

Quantum Physics · Physics 2026-04-14 Jongjun M. Lee

Optical frequency comb, as a spectrum made of discrete and equally spaced spectral lines, is a light source with essential applications in modern technology. Cavity optomechanical systems were found to be a feasible candidate for realizing…

Optics · Physics 2024-08-13 Xin Gu , Jinlian Zhang , Shulin Ding , Xiaoshun Jiang , Bing He , Qing Lin

Exceptional points (EP) featuring enhanced responsivity and rich dynamics have attracted extensive attentions in device developments and sensing applications. However, it remains debated whether employing EP systems is beneficial in…

Optical frequency combs establish a rigid phase-coherent link between microwave and optical domains and are emerging as high-precision tools in an increasing number of applications. Frequency combs with large intermodal spacing are employed…

A numerical algorithm is proposed to explore in a systematic way the trajectories of the eigenvalues of non-Hermitian matrices in the parametric space and exploit this in order to find the locations of defective eigenvalues in the complex…

Computational Physics · Physics 2020-04-08 Benoit Nennig , Emmanuel Perrey-Debain

Non-Hermitian classical and open quantum systems near an exceptional point (EP) are known to undergo strong deviations in their dynamical behavior under small perturbations or slow cycling of parameters as compared to Hermitian systems.…

Quantum Physics · Physics 2021-02-19 Stefano Longhi

Flat band and non-Hermitian are both significant conceptions in modern physics. In this study, we delve into the behaviours of flat bands in non-Hermitian systems, focusing on the interplay between the flat band and its dispersive…

Classical Physics · Physics 2025-01-06 Dongyi Wang , Ruoyang Zhang , Chinghua Lee , Kun Ding , Guancong Ma

Higher-order exceptional points (EPs), which appear as multifold degeneracies in the spectra of non-Hermitian systems, are garnering extensive attention in various multidisciplinary fields. However, constructing higher-order EPs still…