Observation of reflectionless absorption due to spatial Kramers–Kronig profile

Ye, Dexin; Cao, Cheng; Zhou, Tianyi; Huangfu, Jiangtao; Zheng, Guoan; Ran, Lixin

doi:10.1038/s41467-017-00123-4

Cited by 57 publications

(37 citation statements)

References 30 publications

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“…The use of optical circulators with high isolation ratios is another approach. Recently, a novel technique based on Kramers-Kronig relation was also proposed to eliminate reflections [47]. We plan to explore these different design strategies in future work.…”

Section: Appendix Appendix A: Eliminating Reflection From Input Portmentioning

confidence: 99%

Sensing with Exceptional Surfaces in Order to Combine Sensitivity with Robustness

et al. 2019

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Exceptional points (EPs) are singularities that arise in non-Hermitian physics. Current research efforts focus only on systems supporting isolated EPs characterized by increased sensitivity to external perturbations, which makes them potential candidates for building next generation optical sensors. On the downside, this feature is also the Achilles heel of these devices: they are very sensitive to fabrication errors and experimental uncertainties. To overcome this problem, we introduce a new design concept for implementing photonic EPs that combine the robustness required for practical use together with their hallmark sensitivity. Particularly, our proposed structure exhibits a hypersurface of Jordan EPs (JEPs) embedded in a larger space, and having the following peculiar features: (1) A large class of undesired perturbations shift the operating point along the exceptional surface (ES), thus leaving the system at another EP which explains the robustness;(2) Perturbations due to back reflection/scattering force the operating point out of the ES, leading to enhanced sensitivity. Importantly, our proposed geometry is relatively easy to implement using standard photonics components and the design concept can be extended to other physical platforms such as microwave or acoustics. * ganainy@mtu.edu 1 arXiv:1810.09417v1 [physics.optics]

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Section: Appendix Appendix A: Eliminating Reflection From Input Portmentioning

confidence: 99%

Sensing with Exceptional Surfaces in Order to Combine Sensitivity with Robustness

et al. 2019

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“…A fascinating property of such media is that they are one-way or bidirectionally reflectionless, whatever the angle of incidence. Such a property, besides extending our comprehension of the fundamental phenomenon of reflection, may offer new ways for the design of antireflection surfaces and thin materials with efficient light absorption [86,87]. Ongoing research in this area can be found in Refs.…”

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confidence: 99%

Parity-time symmetry meets photonics: A new twist in non-Hermitian optics

Longhi

2017

EPL

312

211

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In the past decade, the concept of parity-time (PT ) symmetry, originally introduced in non-Hermitian extensions of quantum mechanical theories, has come into thinking of photonics, providing a fertile ground for studying, observing, and utilizing some of the peculiar aspects of PT symmetry in optics. Together with related concepts of non-Hermitian physics of open quantum systems, such as non-Hermitian degeneracies (exceptional points) and spectral singularities, PT symmetry represents one among the most fruitful ideas introduced in optics in the past few years. Judicious tailoring of optical gain and loss in integrated photonic structures has emerged as a new paradigm in shaping the flow of light in unprecedented ways, with major applications encompassing laser science and technology, optical sensing, and optical material engineering. In this perspective, I review some of the main achievements and emerging areas of PT -symmetric and non-Hermtian photonics, and provide an outline of challenges and directions for future research in one of the fastest growing research area of photonics.

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“…The scheme succeeds not only in rendering invisible a passively scattering object, characterized by a real susceptibility (with neither gain nor losses), but also for arbitrary complex-valued scattering functions ( , ). The procedure turns out to be more flexible than the spatial KK transform, while also allowing to form objects with topologically complex shapes at higher dimensions as opposed to previous demonstrations 36,37 . Moreover, following an iterative chain of generalized Hilbert transforms, we propose the invisibility on demand with additional constraints, i.e.…”

Section: Discussionmentioning

confidence: 95%

Invisibility on demand based on a generalized Hilbert transform

et al. 2018

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Designing invisible objects without the usage of extreme materials is a long-sought goal for photonic applications. Invisibility techniques demonstrated so far typically require high anisotropy, gain and losses, while also not being flexible. Here we propose an invisibility approach to suppress the scattering of waves from/to given directions and for particular frequency ranges, i.e. invisibility on demand. We derive a Born approximationbased generalized Hilbert transform for a specific invisibility arrangement relating the two quadratures of the complex permittivity of an object. The theoretical proposal is confirmed by numerical calculations, indicating that near-perfect invisibility can be attained for arbitrary objects with low-index contrast. We further demonstrate the cases where the idea can be extended to high-index objects or restricted to within practical limits by avoiding gain areas. The proposed concept opens a new route for the practical implementation of complex-shaped objects with arbitrarily suppressed scatterings determined on demand.Full invisibility, or cloaking, was proposed using transformation optics or, equivalently, conformal mapping 1,2 . The idea is elegant and fascinating; however, it can hardly cross the limits of science fiction, since the complexity of the required metamaterials severely limit practical realizations. Therefore, actual cloaking schemes generally scarify the perfect wavefront reconstruction or operate under a narrow bandwidth, as for instance in carpet cloaking 3-7 , plasmonic cloaking 8,9 , or mantle cloaking with thin patterned metasurfaces 10 , metallic scatterer 11 or dielectric coating 12 based cloaking, among others 13,14 .A completely different approach to the concept of invisibility, referred as "unidirectional invisibility", relays on systems described by non-Hermitian Hamiltonians 15-17 . The concept is based on the property of an object to be invisible when probed by a wave from one side only. Such effect is accomplished by specific complex-modulated potentials (in optical terms: specific refraction index and gain/loss distributions), that allow suppressing the scattering of radiation from an object.Unidirectional invisibility was first proposed for parity-time (PT) symmetric periodical systems (defined by symmetric index modulations accompanied by anti-symmetric gain/loss distributions), close to so-called PT-symmetry breaking point. Initially proposed for narrow frequency bands (due to the resonances of the periodic structure), and for particular incidence directions 18-20 , the idea was extended to broad band radiation (both in frequency and in propagation direction) also by considering non-PT-symmetric potentials 21-25 .More recently, "unidirectional invisibility" has been related to the more general class of non-Hermitian potentials fulfilling the spatial Kramers-Kronig (KK) relations 26 . In the same way as the causality in time imposes KK relations in frequency, analogously, the KK theory may be directly extended to attain unidirectional invisibility...

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Observation of reflectionless absorption due to spatial Kramers–Kronig profile

Cited by 57 publications

References 30 publications

Sensing with Exceptional Surfaces in Order to Combine Sensitivity with Robustness

Sensing with Exceptional Surfaces in Order to Combine Sensitivity with Robustness

Parity-time symmetry meets photonics: A new twist in non-Hermitian optics

Invisibility on demand based on a generalized Hilbert transform

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