scholarly journals Bound states in the continuum in open acoustic resonators

2015 ◽  
Vol 780 ◽  
pp. 370-387 ◽  
Author(s):  
A. A. Lyapina ◽  
D. N. Maksimov ◽  
A. S. Pilipchuk ◽  
A. F. Sadreev
Keyword(s):  
Bound States ◽  
Three Dimensional ◽  
Life Time ◽  
Three Dimensions ◽  
Destructive Interference ◽  
Acoustic Resonators ◽  
Coupled Mode ◽  
Resonant Modes ◽  
Axisymmetric Duct ◽  
The Continuum

We consider bound states in the continuum (BSCs) or embedded trapped modes in two- and three-dimensional acoustic axisymmetric duct–cavity structures. We demonstrate numerically that, under variation of the length of the cavity, multiple BSCs occur due to the Friedrich–Wintgen two-mode full destructive interference mechanism. The BSCs are detected by tracing the resonant widths to the points of the collapse of Fano resonances where one of the two resonant modes acquires infinite life-time. It is shown that the approach of the acoustic coupled mode theory cast in the truncated form of a two-mode approximation allows us to analytically predict the BSC frequencies and shape functions to a good accuracy in both two and three dimensions.

RETARDATION EFFECTS IN COVARIANT THREE-DIMENSIONAL BOUND STATE WAVE FUNCTIONS

2005 ◽  
Vol 14 (06) ◽  
pp. 931-947 ◽  
Author(s):  
F. PILOTTO ◽  
M. DILLIG
Keyword(s):  
Bound States ◽  
Three Dimensional ◽  
Bound State ◽  
Relative Energy ◽  
Wave Functions ◽  
Three Dimensions ◽  
State Wave ◽  
Scalar Diquark ◽  
Bound State Wave Function ◽  
Retardation Effects

We investigate the influence of retardation effects on covariant 3-dimensional wave functions for bound hadrons. Within a quark-(scalar) diquark representation of a baryon, the four-dimensional Bethe–Salpeter equation is solved for a 1-rank separable kernel which simulates Coulombic attraction and confinement. We project the manifestly covariant bound state wave function into three dimensions upon integrating out the non-static energy dependence and compare it with solutions of three-dimensional quasi-potential equations obtained from different kinematical projections on the relative energy variable. We find that for long-range interactions, as characteristic in QCD, retardation effects in bound states are of crucial importance.

scholarly journals Active angular tuning and switching of Brewster quasi bound states in the continuum in magneto-optic metasurfaces

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Diego R. Abujetas ◽  
Nuno de Sousa ◽  
Antonio García-Martín ◽  
José M. Llorens ◽  
José A. Sánchez-Gil
Keyword(s):  
Magnetic Field ◽  
Magnetic Dipole ◽  
Bound States ◽  
Electromagnetic Spectrum ◽  
Resonant Modes ◽  
Out Of Plane ◽  
Q Factors ◽  
The Impact ◽  
The Continuum ◽  
Magneto Optic

Abstract Bound states in the continuum (BICs) emerge throughout physics as leaky/resonant modes that remain, however, highly localized. They have attracted much attention in photonics, and especially in metasurfaces. One of their most outstanding features is their divergent Q-factors, indeed arbitrarily large upon approaching the BIC condition (quasi-BICs). Here, we investigate how to tune quasi-BICs in magneto-optic (MO) all-dielectric metasurfaces. The impact of the applied magnetic field in the BIC parameter space is revealed for a metasurface consisting of lossless semiconductor spheres with MO response. Through our coupled electric/magnetic dipole formulation, the MO activity is found to manifest itself through the interference of the out-of-plane electric/magnetic dipole resonances with the (MO-induced) in-plane magnetic/electric dipole, leading to a rich, magnetically tuned quasi-BIC phenomenology, resembling the behavior of Brewster quasi-BICs for tilted vertical-dipole resonant metasurfaces. Such resemblance underlies our proposed design for a fast MO switch of a Brewster quasi-BIC by simply reversing the driving magnetic field. This MO-active BIC behavior is further confirmed in the optical regime for a realistic Bi:YIG nanodisk metasurface through numerical calculations. Our results present various mechanisms to magneto-optically manipulate BICs and quasi-BICs, which could be exploited throughout the electromagnetic spectrum with applications in lasing, filtering, and sensing.

scholarly journals Rotational symmetry of photonic bound states in the continuum

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Liangsheng Li ◽  
Yunzhou Li ◽  
Yong Zhu ◽  
Hongcheng Yin
Keyword(s):  
Photonic Crystal ◽  
Bound States ◽  
Layer Structure ◽  
Rotational Symmetry ◽  
Coupled Model ◽  
Numerical Data ◽  
Life Time ◽  
Layer Structures ◽  
Radiation Decay ◽  
The Continuum

Abstract The bound states in the continuum (BICs) have been investigated by simulating the optical reflectivity of a tri-layer photonic crystal slab. We found that optical BICs can occur in a class of photonic crystal systems with $$c_{1}^{z}$$ c 1 z , $$c_{2}^{z}$$ c 2 z or $$c_{4}^{z}$$ c 4 z rotational symmetries, which are constructed by three identical photonic crystal slabs. By applying the two mode coupled model, we obtain the reflectivity formula to fit the numerical data and evaluate the lifetime of radiation decay. In vicinity of BIC, the lifetime diverges as a power law form, when approaching the BIC point. The infinity life time of $$c_{1}^{z} {\text{ } - \text{ BIC}}$$ c 1 z - BIC in the tri-layer structure indicate that it is a true BIC. The $$c_{1}^{z} {\text{ } - \text{ BIC}}$$ c 1 z - BIC occurs robustly in tri-layer structures, but the resonance frequency of the BICs is dependent on the permittivity of slab, air-hole size and hole shape.

scholarly journals Sensitive THz sensing based on Fano resonance in all-polymeric Bloch surface wave structure

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Chi Zhang ◽  
Qiang Liu ◽  
Xiao Peng ◽  
Zhengbiao Ouyang ◽  
Suling Shen
Keyword(s):  
Surface Wave ◽  
Quality Factor ◽  
Fano Resonance ◽  
Bound States ◽  
High Sensitivity ◽  
Influential Factors ◽  
Destructive Interference ◽  
Optimized Design ◽  
Bloch Surface Wave ◽  
The Continuum

Abstract Simultaneous realization of high quality factor (Q), sensitivity, and figure of merit (FOM) play a pivotal role in building the THz sensor. For such purpose, we propose an all-polymeric Bloch surface wave (BSW) structure that supports a bright BSW mode and a dark surface Fano state that is embedded in the continuum, both of which coupled to the same radiation channels. The existence of the sharp dip with a maximum depth of Fano line could be interpreted with the physics of Friedrich–Wintgen bound states in the continuum (FW-BICs), because of the destructive interference between bright BSW and dark surface Fano modes. A strong angular- and frequency-dependent Q was found. Related influential factors to Q value may also include an asymmetric arrangement of top and grating layers, together with the weak coupling provided by photonic crystals. One numerically optimized design shows a quality factor Q of the Fano mode as 23,670, which is almost two orders higher than that in conventional metallic-metamaterial-based designs. The optimized sensitivity can numerically reach 4.34 THz/RIU in the frequency domain, which is one order higher than that reported in all-dielectric metasurfaces. We infer the high sensitivity is related to the phase-matching condition provided by near-subwavelength gratings. The associated FOM can reach 8857/RIU. Besides, the proposed design also numerically demonstrates high sensitivity in the angular domain ∼125.5°/RIU. Considering it poses no specific requirement for materials that own high contrast of permittivity in the THz regime, large interfacing area, the mechanical and chemical robustness offered by polymers and low cost in fabrication, such all-polymeric BSW structure that supports novel Fano resonance in THz window may give access to rich applications in hazardous gas detection and label-free bio-sensing.

Cellular Automaton Simulations of Surface Mass Transport Due to Curvature Gradients: Simulations of Sintering in 3-D.

1991 ◽  
Vol 249 ◽  
Author(s):  
D.P. Bentz ◽  
P.J.P. Pimienta ◽  
E.J. Garboczi ◽  
W.C. Carter
Keyword(s):  
Cellular Automaton ◽  
Scaling Laws ◽  
Chemical Potential ◽  
Pore Space ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Computation Method ◽  
Surface Mass ◽  
Digital Version ◽  
The Continuum

ABSTRACTA cellular automaton algorithm is described that simulates the evolution of a surface driven by the reduction of chemical potential differences on the surface. When the surface tension is isotropic, the chemical potential is proportional to the curvature at the surface. This process is important in the development of microstructure during the sintering of powders. The algorithm is implemented in two and three dimensions in a digital image mode, using discrete pixels to represent continuum objects. The heart of the algorithm is a pixel-counting-based method for computing the potential at a pixel located in a digital surface. This method gives an approximate measure of the curvature at the given surface pixel. The continuum version of this method is analytically shown to give the true curvature at a point on a continuum surface. The digital version of the curvature computation method is shown to obey the scaling laws derived for the continuum version. The evolution of the surface of a three dimensional loosely packed powder, along with the percolation characteristics of its pore space, are computed as an example of the algorithm.

LOW DENSITY HUBBARD MODEL IN TWO AND THREE DIMENSIONS

1992 ◽  
Vol 06 (12) ◽  
pp. 753-760
Author(s):  
S. YU. KHLEBNIKOV
Keyword(s):  
Scattering Length ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Low Density ◽  
Two Dimensional ◽  
Three Dimensional Model ◽  
Hubbard Models ◽  
Short Range Repulsion ◽  
Upper Half Plane ◽  
The Continuum

We consider two- and three-dimensional repulsive Hubbard models at low density, using the gas approximation. The large-U three-dimensional model is shown to behave as a Fermi liquid and the corresponding two-particle scattering length is found. In the two-dimensional case we find that the gas approximation is inconsistent, as indicated by an isolated pole of the two-particle Green function below the occupied states in the upper half-plane. This behaviour is specific to the lattice system as opposed to the continuum two-dimensional Fermi gas with short-range repulsion.

MASS MATRICES AND MONOPOLES IN THREE-DIMENSIONAL FLUX PHASE MODELS

1992 ◽  
Vol 06 (25) ◽  
pp. 1569-1576
Author(s):  
G.C. SEGRE
Keyword(s):  
Bound States ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Spin States ◽  
Mass Matrices ◽  
Phase Models

Chiral spin states in two dimensions can be generalized to three dimensions by introducing effective monopoles to generate the background fluxes. We explore some generalizations of chiral spin states and the consequences of chiral rotations on the charges of dyons, particle-monopole bound states.

scholarly journals Bound states in the continuum in strong-coupling and weak-coupling regimes under the cylinder – ring transition

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nikolay Solodovchenko ◽  
Kirill Samusev ◽  
Daria Bochek ◽  
Mikhail Limonov
Keyword(s):  
Strong Coupling ◽  
Weak Coupling ◽  
Bound States ◽  
Dielectric Cylinder ◽  
Weak Coupling Regime ◽  
Field Zone ◽  
The Past ◽  
Resonant Modes ◽  
Avoided Crossing ◽  
The Continuum

Abstract Bound states in the continuum (BIC) have been at the forefront of research in optics and photonics over the past decade. It is of great interest to study the effects associated with quasi-BICs in the simplest structures, where quasi-BICs are very pronounced. An example is a dielectric cylinder, and in a number of works, quasi-BICs have been studied both in single cylinders and in structures composed of cylinders. In this work, we studied the properties of quasi-BICs during the transition from a homogeneous dielectric cylinder in an air environment to a ring with narrow walls while increasing the diameter of the inner air cylinder gradually. The results demonstrate the quasi-BIC crossover from the strong-coupling to the weak-coupling regime, which manifests itself in the transition from the avoided crossing of branches to their intersection with the quasi-BIC being preserved on only one straight branch. In the regime of strong-coupling and quasi-BIC, three waves interfere in the far-field zone: two waves corresponding to the resonant modes of the structure and the wave scattered by the structure as a whole. The validity of the Fano resonance concept is discussed since it describes the interference of only two waves under weak coupling conditions.

scholarly journals Three-dimensional Majorana fermions in chiral superconductors

2016 ◽  
Vol 2 (12) ◽  
pp. e1601835 ◽  
Author(s):  
Vladyslav Kozii ◽  
Jörn W. F. Venderbos ◽  
Liang Fu
Keyword(s):  
Angular Momentum ◽  
Bound States ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Majorana Fermions ◽  
Spin Orbit ◽  
Nuclear Spins ◽  
Topology Analysis ◽  
Resonance Spin ◽  
Comprehensive Classification

Using a systematic symmetry and topology analysis, we establish that three-dimensional chiral superconductors with strong spin-orbit coupling and odd-parity pairing generically host low-energy nodal quasiparticles that are spin-nondegenerate and realize Majorana fermions in three dimensions. By examining all types of chiral Cooper pairs with total angular momentumJformed by Bloch electrons with angular momentumjin crystals, we obtain a comprehensive classification of gapless Majorana quasiparticles in terms of energy-momentum relation and location on the Fermi surface. We show that the existence of bulk Majorana fermions in the vicinity of spin-selective point nodes is rooted in the nonunitary nature of chiral pairing in spin-orbit–coupled superconductors. We address experimental signatures of Majorana fermions and find that the nuclear magnetic resonance spin relaxation rate is significantly suppressed for nuclear spins polarized along the nodal direction as a consequence of the spin-selective Majorana nature of nodal quasiparticles. Furthermore, Majorana nodes in the bulk have nontrivial topology and imply the presence of Majorana bound states on the surface, which form arcs in momentum space. We conclude by proposing the heavy fermion superconductor PrOs4Sb12and related materials as promising candidates for nonunitary chiral superconductors hosting three-dimensional Majorana fermions.

scholarly journals Are there bound states in the continuum in a dielectric ring?

2021 ◽  
Vol 2015 (1) ◽  
pp. 012017
Author(s):  
D V Bochek ◽  
N S Solodovchenko ◽  
K B Samusev ◽  
M F Limonov
Keyword(s):  
Electromagnetic Waves ◽  
Bound States ◽  
Basic Research ◽  
Destructive Interference ◽  
Field Zone ◽  
Physical Mechanisms ◽  
Photonic States ◽  
Quality Factor Q ◽  
Dielectric Structures ◽  
The Continuum

Abstract Trapping and confining electromagnetic waves is important in both basic research and a variety of applications. For these purposes, various physical mechanisms are exploited including bound states in the continuum, which have been actively investigated recently. Bound states in the continuum have been observed in various objects consisting of both one and a number of dielectric structures. In particular, these photonic states were observed in high-contrast dielectric cylinders in the regime of strong eigenmode coupling, which leads to destructive interference in the far-field zone. In this article, we present the results of a study of bound states in a continuum in a dielectric ring, i.e. cylinder with coaxial air hole. The dependence of the quality factor Q on the normalized diameter of the hole is discussed.

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