Emulating exceptional-point encirclements using imperfect (leaky) photonic components: asymmetric mode-switching and omni-polarizer action

Khurgin, Jacob B.; Sebbag, Yoel; Edrei, Eitan; Zektzer, Roy; Shastri, Kunal; Levy, Uriel; Monticone, Francesco

doi:10.1364/optica.412981

Cited by 27 publications

(18 citation statements)

References 35 publications

(8 reference statements)

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“…These two regimes are separated by the EP, where the eigenvalues coalesce. Structures with a global net loss, e.g., plasmonic [12,38] and leaky [51] waveguides, share many of the same features as non-Hermitian systems with no net loss: the main difference is that eigenvalues are shifted along the positive imaginary axis with respect to the perfectly loss-balanced case. Coupled lossy systems can thus be more rigorously classified as having eigenvalues that are either effective P T -symmetric (EPTS) or effective P T -broken (EPTB), as labelled in Fig.…”

Section: Modesmentioning

confidence: 99%

Influence of non-Hermitian mode topology on refractive index sensing with plasmonic waveguides

Tuniz,

Schmidt,

Kuhlmey

2021

Preprint

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We evaluate the sensing properties of plasmonic waveguide sensors by calculating their resonant transmission spectra in different regions of the non-Hermitian eigenmode space. We elucidate the pitfalls of using modal dispersion calculations in isolation to predict plasmonic sensor performance, which we address by using a simple model accounting for eigenmode excitation and propagation. Our transmission calculations show that resonant wavelength and spectral width crucially depend on the length of the sensing region, so that no single criterion obtained from modal dispersion calculations alone can be used as a proxy for sensitivity. Furthermore, we find that the optimal detection limits occur where directional coupling is supported, where the narrowest spectra occur. Such narrow spectral features can only be measured by filtering out all higher-order modes at the output, e.g., via a single-mode waveguide. Our calculations also confirm a characteristic square root dependence of the eigenmode splitting with respect to the permittivity perturbation at the exceptional point, which we show can be identified through the sensor beat length at resonance. This work provides a convenient framework for designing and characterizing plasmonic waveguide sensors when comparing with experimental measurements.

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Section: Modesmentioning

confidence: 99%

Influence of non-Hermitian mode topology on refractive index sensing with plasmonic waveguides

Tuniz,

Schmidt,

Kuhlmey

2021

Preprint

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“…This setup is per se not restricted to the paraxial approximation, as it may be applied to numerous optical problems [4,9,15,16]. It has turned out to be a fertile ground for a new field of photonics, gaining many fundamental results and application proposals, including sensitivity enhancement [17][18][19][20][21], PT -symmetric lasers [22][23][24], and PT -symmetric optical diodes based on nonreciprocal light propagation [25,26].…”

Section: Introductionmentioning

confidence: 99%

Fundamental issues with light propagation through $\mathcal{PT}$-symmetric systems

Shuklin,

Tserkezis,

Mortensen

et al. 2022

Preprint

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We analyse the emergence of unphysical superluminal group velocities in Su-Schrieffer-Heeger (SSH) parity-time (PT ) symmetric chains, and explore the origins of such a behaviour. By comparing the band structure of an infinite loss-gain SSH chain with that of a one-dimensional Bragg stack, we first exclude insufficient coupling consideration in the tight-binding description as the cause of group-velocity divergence. We then focus on material dispersion, and show that indeed, restoring causality in the description of both the lossy and the gain components resolves the problem and recovers finite group velocities, whose real part can only exceed the speed of light in vacuum when accompanied by a significant imaginary part. Our analysis introduces thus the required practical limits in the performance of common PT -symmetric systems.

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“…1F) ( 9 , 19 – 25 ). Although this chiral behavior has recently been observed in a number of physical systems ( 9 , 20 – 22 , 24 , 26 ), little has been done to exploit this concept to establish a purely topological state in non-Hermitian configurations ( 27 – 29 ).…”

mentioning

confidence: 99%

“…Apart from its counterintuitive behavior, this laser constitutes an adiabatic non-Hermitian cavity that supports a fully topological resonant mode. The implementation of EP encircling with gain additionally avoids the considerable absorption losses that plagued previous reports of chiral state transfer with dissipative elements ( 9 , 20 – 22 , 24 , 26 ). Furthermore, because the topological energy transfer relies solely on the adiabatic encircling of an EP degeneracy and not on the exact shape of the loop, the resulting lasing mode is robust against defects and fabrication imperfections, as well as fluctuations in gain [see the materials and methods ( 30 ), sections 5 and 6].…”

mentioning

confidence: 99%

Topological modes in a laser cavity through exceptional state transfer

Schumer

Liu

Leshin

et al. 2022

Science

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Shaping the light emission characteristics of laser systems is of great importance in various areas of science and technology. In a typical lasing arrangement, the transverse spatial profile of a laser mode tends to remain self-similar throughout the entire cavity. Going beyond this paradigm, we demonstrate here how to shape a spatially evolving mode such that it faithfully settles into a pair of bi-orthogonal states at the two opposing facets of a laser cavity. This was achieved by purposely designing a structure that allows the lasing mode to encircle a non-Hermitian exceptional point while deliberately avoiding non-adiabatic jumps. The resulting state transfer reflects the unique topology of the associated Riemann surfaces associated with this singularity. Our approach provides a route to developing versatile mode-selective active devices and sheds light on the interesting topological features of exceptional points.

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Emulating exceptional-point encirclements using imperfect (leaky) photonic components: asymmetric mode-switching and omni-polarizer action

Cited by 27 publications

References 35 publications

Influence of non-Hermitian mode topology on refractive index sensing with plasmonic waveguides

Influence of non-Hermitian mode topology on refractive index sensing with plasmonic waveguides

Fundamental issues with light propagation through $\mathcal{PT}$-symmetric systems

Topological modes in a laser cavity through exceptional state transfer

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