scholarly journals Bound states in the continuum and strong phase resonances in integrated Gires-Tournois interferometer

Nanophotonics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 83-92 ◽  
Author(s):  
Dmitry A. Bykov ◽  
Evgeni A. Bezus ◽  
Leonid L. Doskolovich
Keyword(s):  
Bound States ◽  
Resonance Effect ◽  
Wave Model ◽  
Slab Waveguide ◽  
Strong Phase ◽  
Practical Applications ◽  
Wide Range ◽  
On Chip ◽  
The Continuum ◽  
Phase Resonance

AbstractPhotonic bound states in the continuum (BICs) are eigenmodes with an infinite lifetime, which coexist with a continuous spectrum of radiating waves. BICs are not only of great theoretical interest but also have a wide range of practical applications, e.g. in the design of optical resonators. Here, we study this phenomenon in a new integrated nanophotonic element consisting of a single dielectric ridge terminating an abruptly ended slab waveguide. This structure can be considered as an on-chip analog of the Gires-Tournois interferometer (GTI). We demonstrate that the proposed integrated structure supports high-Q phase resonances and robust BICs. We develop a simple but extremely accurate coupled-wave model that clarifies the physics of BIC formation and enables predicting BIC locations. The developed model shows that the studied BICs are topologically protected and describes the strong phase resonance effect that occurs when two BICs with opposite topological charges annihilate.

scholarly journals Bound states in the continuum and high-Q resonances supported by a dielectric ridge on a slab waveguide

2018 ◽  
Vol 6 (11) ◽  
pp. 1084 ◽  
Author(s):  
Evgeni A. Bezus ◽  
Dmitry A. Bykov ◽  
Leonid L. Doskolovich
Keyword(s):  
Bound States ◽  
Slab Waveguide ◽  
High Q ◽  
The Continuum

scholarly journals Displacement-mediated bound states in the continuum in all-dielectric superlattice metasurfaces

PhotoniX ◽  
2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Tan Shi ◽  
Zi-Lan Deng ◽  
Qing-An Tu ◽  
Yaoyu Cao ◽  
Xiangping Li
Keyword(s):  
Bound States ◽  
Relative Displacement ◽  
Localized States ◽  
Practical Applications ◽  
High Q ◽  
Magnetic Mode ◽  
Toroidal Mode ◽  
Resonance Coupling ◽  
Field Symmetry ◽  
The Continuum

AbstractBound states in the continuum (BICs) are localized states coexisting with extended waves inside the continuous spectrum range, which have infinite lifetimes without any radiation. To extract high-Q quasi-BIC resonances from the symmetry-protected BIC for practical applications, symmetry-breaking approaches are usually exploited, either by slightly breaking the excitation field symmetry or structure symmetry. Here, we introduce an all-dielectric superlattice metasurface that can symmetry-compatibly convert BIC states into high-Q quasi-BIC modes based on the guided-mode resonance coupling by relative displacement tuning. The metasurface is composed of a superlattice of multiple nanobeams, supporting both magnetic mode and toroidal mode with large tunability. Both modes can interact with the incident continuum by mediating the displacement between nanobeams, which empowers dual asymmetric Fano resonances with high Q-factors. The bandwidth of the toroidal mode under y-polarized incidences and that of the magnetic mode under x-polarized incidences can be readily tuned by the local displacement between nanobeams in each unit cell. Such displacement-mediated BIC resonance is promising for various applications such as bio-molecule sensing and low threshold lasing.

scholarly journals Displacement-mediated bound states in the continuum in all-dielectric superlattice metasurfaces

2021 ◽  
Author(s):  
Tan Shi ◽  
Zilan Deng ◽  
Qing-An Tu ◽  
Yaoyu Cao ◽  
Xiangping Li
Keyword(s):  
Bound States ◽  
Relative Displacement ◽  
Localized States ◽  
Practical Applications ◽  
High Q ◽  
Magnetic Mode ◽  
Toroidal Mode ◽  
Resonance Coupling ◽  
Field Symmetry ◽  
The Continuum

Abstract Bound states in the continuum (BICs) are localized states coexisting with extended waves inside the continuous spectrum range, which have infinite lifetimes without any radiation. To extract high-Q quasi-BIC resonances from the symmetry-protected BIC for practical applications, symmetry-breaking approaches are usually exploited, either by slightly breaking the excitation field symmetry or structure symmetry. Here, we introduce an all-dielectric superlattice metasurface that can symmetry-compatibly convert BIC states into high-Q quasi-BIC modes based on the guided-mode resonance coupling by relative displacement tuning. The metasurface is composed of a superlattice of multiple nanobeams, supporting both magnetic mode and toroidal mode with large tunability. Both modes can interact with the incident continuum by mediating the displacement between nanobeams, which empowers dual asymmetric Fano resonances with high Q-factors. The bandwidth of the toroidal mode under TE-polarized incidences and that of the magnetic mode under TM-polarized incidences can be readily tuned by the local displacement between nanobeams in each unit cell. Such displacement-mediated BIC resonance is promising for various applications such as bio-molecule sensing and low threshold lasing.

scholarly journals Observation of miniaturized bound states in the continuum with ultra-high quality factors

2021 ◽  
Author(s):  
Zihao Chen ◽  
Xuefan Yin ◽  
Jicheng Jin ◽  
Zhao Zheng ◽  
Zixuan Zhang ◽  
...  
Keyword(s):  
Bound States ◽  
Photonic Band Gap ◽  
Light Trapping ◽  
Vertical Direction ◽  
Three Dimensions ◽  
Quality Factors ◽  
High Quality ◽  
Potential Applications ◽  
On Chip ◽  
The Continuum

Abstract Light trapping is a constant pursuit in photonics because of its importance in science and technology. Many mechanisms have been explored, including the use of mirrors made of materials or structures that forbid outgoing waves, and bound states in the continuum that are mirror-less but based on topology. Here we report a compound method, combing mirrors and bound states in the continuum in an optimized way, to achieve a class of on-chip optical cavities that have high quality factors and small modal volumes. Specifically, light is trapped in the transverse direction by the photonic band gap of the lateral hetero-structure and confined in the vertical direction by the constellation of multiple bound states in the continuum. As a result, unlike most bound states in the continuum found in photonic crystal slabs that are de-localized Bloch modes, we achieve light-trapping in all three dimensions and experimentally demonstrate quality factors as high as Q = 1.09×106 and modal volumes as low as V = 3.56 μm3 in the telecommunication regime. We further prove the robustness of our method through the statistical study of multiple fabricated devices. Our work provides a new method of light trapping, which can find potential applications in photonic integration, nonlinear optics and quantum computing.

scholarly journals Graphene perfect absorber with loss adaptive Q-factor control function enabled by quasi-bound states in the continuum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sangjun Lee ◽  
Joohyung Song ◽  
Sangin Kim
Keyword(s):  
Bound States ◽  
Control Function ◽  
Incident Angle ◽  
Leakage Rate ◽  
Slab Waveguide ◽  
Monolayer Graphene ◽  
Perfect Absorber ◽  
Coupling Condition ◽  
Perfect Absorption ◽  
The Continuum

AbstractNumerous device structures have been proposed for perfect absorption in monolayer graphene under single-sided illumination, all of which requires the critical coupling condition, i.e., the balance between the loss of graphene and the leakage rate of the device. However, due to the difficulty of the precise control of the quality of synthesized graphene and unwanted doping in graphene transferred to the substrate, the loss of graphene is rather unpredictable, so that the perfect absorption is quite difficult to achieve in practice. To solve this problem, we designed a novel perfect absorber structure with a loss adaptive leakage rate control function enabled by the quasi-bound states in the continuum (BIC) and numerically demonstrated its performance. Our designed device is based on a slab-waveguide grating supporting both the quasi-BIC and the guided-mode resonance (GMR); the quasi-BIC with an adjustable leakage rate controlled by an incident angle is responsible for absorption, while the GMR works as an internal mirror. Since the proposed device scheme can have an arbitrarily small leakage rate, it can be used to implement a perfect absorber for any kind of ultrathin absorbing media. Due to the simple structure avoiding an external reflector, the device is easy to fabricate.

scholarly journals Topological polarization singularities in metaphotonics

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wenzhe Liu ◽  
Wei Liu ◽  
Lei Shi ◽  
Yuri Kivshar
Keyword(s):  
Bound States ◽  
Mie Theory ◽  
Optical Vortices ◽  
Wave Optics ◽  
Scalar Wave ◽  
Practical Applications ◽  
Field Patterns ◽  
Phase Singularities ◽  
Topological Charges ◽  
The Continuum

Abstract Polarization singularities of vectorial electromagnetic fields locate at the positions where properties of polarization ellipses are not defined. First observed for conical diffraction in 1830s, polarization singularities have been studied systematically with the underlying concepts being reshaped and deepened by many pioneers of wave optics. Here we review the recent results on the generation and observation of polarization singularities in metaphotonics. We start with the discussion of polarization singularities in the Mie theory, where both electric and magnetic multipoles are explored from perspectives of local and global polarization properties. We then proceed with the discussion of various photonic-crystal structures, for which both near- and far-field patterns manifest diverse polarization singularities characterized by the integer Poincaré or more general half-integer Hopf indices (topological charges). Next, we review the most recent studies of conversions from polarization to phase singularities in scalar wave optics, demonstrating how bound states in the continuum can be exploited to generate directly optical vortices of various charges. Throughout our paper, we discuss and highlight several fundamental concepts and demonstrate their close connections and special links to metaphotonics. We believe polarization singularities can provide novel perspectives for light-matter manipulation for both fundamental studies and their practical applications.

A New Detector System For The HB5 Stem Instrument

1985 ◽  
Vol 43 ◽  
pp. 134-135
Author(s):  
J.M. Cowley
Keyword(s):  
Dark Field ◽  
Detector System ◽  
Electron Holography ◽  
Small Specimen ◽  
Bright Field ◽  
Multiple Images ◽  
Practical Applications ◽  
Wide Range ◽  
Diffraction Patterns ◽  
Operational Modes

The HB5 STEM instrument at ASU has been modified previously to include an efficient two-dimensional detector incorporating an optical analyser device and also a digital system for the recording of multiple images. The detector system was built to explore a wide range of possibilities including in-line electron holography, the observation and recording of diffraction patterns from very small specimen regions (having diameters as small as 3Å) and the formation of both bright field and dark field images by detection of various portions of the diffraction pattern. Experience in the use of this system has shown that sane of its capabilities are unique and valuable. For other purposes it appears that, while the principles of the operational modes may be verified, the practical applications are limited by the details of the initial design.

Bound states in the continuum in double-hole array perforated in a layer of photonic crystal slab

2019 ◽  
Vol 12 (12) ◽  
pp. 125002 ◽  
Author(s):  
Suxia Xie ◽  
Changzhong Xie ◽  
Song Xie ◽  
Jie Zhan ◽  
Zhijian Li ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Bound States ◽  
Hole Array ◽  
Photonic Crystal Slab ◽  
The Continuum
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