Polarization Singularities of Photonic Quasicrystals in Momentum Space

Che, Zhiyuan; Zhang, Yanbin; Liu, Wenzhe; Zhao, M. G.; Wang, Jiajun; Zhang, Wenjie; Guan, Fang; Liu, Xiaohan; Liu, Wei; Shi, Lei; Zi, Jian

doi:10.1103/physrevlett.127.043901

Cited by 30 publications

(14 citation statements)

References 68 publications

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“…We have discussed the merits of BICs with topological charges −2 at Γ, and more flexible schemes can be devised if one considers BICs with topological charges larger than 2 (see, e.g., ref. 49 ). Merging BICs with robust Q factors (Supplementary Section V ) can boost light-matter interaction, such as nonlinear and quantum effects, and improve the performance of optoelectronic devices.…”

Section: Discussionmentioning

confidence: 99%

Merging bound states in the continuum by harnessing higher-order topological charges

et al. 2022

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Bound states in the continuum (BICs) can confine light with a theoretically infinite Q factor. However, in practical on-chip resonators, scattering loss caused by inevitable fabrication imperfection leads to finite Q factors due to the coupling of BICs with nearby radiative states. Merging multiple BICs can improve the robustness of BICs against fabrication imperfection by improving the Q factors of nearby states over a broad wavevector range. To date, the studies of merging BICs have been limited to fundamental BICs with topological charges ±1. Here we show the unique advantages of higher-order BICs (those with higher-order topological charges) in constructing merging BICs. Merging multiple BICs with a higher-order BIC can further improve the Q factors compared with those involving only fundamental BICs. In addition, higher-order BICs offer great flexibility in realizing steerable off-Γ merging BICs. A higher-order BIC at Γ can split into a few off-Γ fundamental BICs by reducing the system symmetry. The split BICs can then be tuned to merge with another BIC, e.g., an accidental BIC, at an off-Γ point. When the in-plane mirror symmetry is further broken, merging BICs become steerable in the reciprocal space. Merging BICs provide a paradigm to achieve robust ultrahigh-Q resonances, which are important in enhancing nonlinear and quantum effects and improving the performance of optoelectronic devices.

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Section: Discussionmentioning

confidence: 99%

Merging bound states in the continuum by harnessing higher-order topological charges

et al. 2022

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“…The topological property guarantees the robustness of BIC against change of system's parameters. Recently, modulating polarization of light and exploring polarization singularities using PhCS has been of greet interest due to abundant polarization features emerging in momentum space [17][18][19][20] . To overcome the limit of only linearly polarized resonance around BIC, the in-plane inversion symmetry of square PhCS is broken into trapezoid and triangle, which causes the V point at BIC decomposed into two circular polarized states (C points) and equator lines on the Poincaré sphere (L lines) 10,21 .…”

Section: Introductionmentioning

confidence: 99%

Arbitrarily polarized bound states in the continuum with twisted photonic crystal slabs

Qin

Liu

et al. 2023

Light Sci Appl

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Arbitrary polarized vortex beam induced by polarization singularity offers a new platform for both classical optics and quantum entanglement applications. Bound states in the continuum (BICs) have been demonstrated to be associated with topological charge and vortex polarization singularities in momentum space. For conventional symmetric photonic crystal slabs (PhCSs), BIC is enclosed by linearly polarized far fields with winding angle of 2π, which is unfavorable for high-capacity and multi-functionality integration-optics applications. Here, we show that by breaking σz-symmetry of the PhCS, asymmetry in upward and downward directions and arbitrarily polarized BIC can be realized with a bilayer-twisted PhCS. It exhibits elliptical polarization states with constant ellipticity angle at every point in momentum space within the vicinity of BIC. The topological nature of BIC reflects on the orientation angle of polarization state, with a topological charge of 1 for any value of ellipticity angle. Full coverage of Poincaré sphere (i.e., $$- {{\pi \over 4}} \le \chi \le {{\pi \over 4}}$$ − π 4 ≤ χ ≤ π 4 and $$- {{\pi \over 2}} \le \psi \le {{\pi \over 2}}$$ − π 2 ≤ ψ ≤ π 2 ) and higher-order Poincaré sphere can be realized by tailoring the twist angles. Our findings may open up new avenues for applications in structured light, quantum optics, and twistronics for photons.

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“…[19,20] With the coupling between leaky resonances and guided modes, photonic BICs are actually vortex centers or polarization singularities in the momentum space. [21] Recently, based on the topological polarization singularities of symmetry-protected and accidental BICs, [22,23] researchers have developed more and more fascinating optical effects such as merging BICs, [24,25] topological protected charges when varying the geometric parameters, [19] generation and annihilation of BICs, [26] chiral BICs generation, [27,28] parity-time symmetry-induced BIC, [29] and enhanced nonlinear generation. [30,31] The abundant optical resonances and mode interactions supported by the optical nanostructures further enable the multidimensional manipulation of optical waves from near field to far field.…”

Section: Introductionmentioning

confidence: 99%

Design Strategies and Applications of Dimensional Optical Field Manipulation Based on Metasurfaces

Liu

Ansari

et al. 2023

Advanced Materials

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Recent rapid progress in metasurfaces is underpinned by the physics of local and nonlocal resonances and the modes coupling among them, leading to tremendous applications such as optical switching, information transmission, and sensing. In this review paper, an overview of the recent advances in a broad range of dimensional optical field manipulation based on metasurfaces categorized into different classes based on design strategies is provided. This review starts from the near‐field optical resonances of artificial nanostructures and discusses the far‐field optical wave manipulation based on fundamental mechanisms such as mode generation and mode coupling. The recent advances in optical field manipulation based on metasurfaces in different optical dimensions such as phase and polarization are summarized, and newly‐developed dimensions such as the orbital angular momentum and the coherence dimensions resulting from phase modulation are discussed. Then, the recent achievements of multiplexing and multifunctional metasurfaces empowered by multidimensional optical field manipulation for optical information transmission and integrated applications are reviewed. Finally, the paper concludes with a few perspectives on emerging trends, possible directions, and existing challenges in this fast‐developing field.

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Polarization Singularities of Photonic Quasicrystals in Momentum Space

Cited by 30 publications

References 68 publications

Merging bound states in the continuum by harnessing higher-order topological charges

Merging bound states in the continuum by harnessing higher-order topological charges

Arbitrarily polarized bound states in the continuum with twisted photonic crystal slabs

Design Strategies and Applications of Dimensional Optical Field Manipulation Based on Metasurfaces

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