Numerical Studies on Band-Gap Structures and Resonant-Mode Wave-Guides of Typical Sonic Crystals Made of Rigid Cylinders in Fluid by Means of Elastic FDTD Method

2005 ◽  
Author(s):  
Toyokatsu Miyashita
Keyword(s):  
Band Gap ◽  
Fdtd Method ◽  
Transmission Band ◽  
Resonant Mode ◽  
Mode Wave ◽  
Periodic Arrays ◽  
Sonic Crystal ◽  
Wave Guides ◽  
Periodic Repetition ◽  
Fdtd Methods

We have investigated band-gap structures of three typical sonic/phononic crystals, namely periodic arrays of methacrylic resin cylinders in air, aluminum cylinders in air, and steel cylinders in water, by two different FDTD methods; one method is a sonic one that deals with only longitudinal waves, and the other is an elastic one that includes also shear waves. We show that both FDTD methods give almost the same band-gap structures for the former two crystals. Namely, the band-gaps by the sonic FDTD method lie at higher frequency only by 0.01 ~ 0.02 in the normalized frequency than those by the elastic one. The theoretical band-gap structures agree well with the experimental ones. In contrast, it is shown that the third crystal should be analyzed by the elastic FDTD method. Resonant-mode wave-guides are made by a periodic repetition of single-defects along a line in a sonic crystal of rigid cylinders in air. The obtained resonant and well-guided transmission band lies inside the full band-gap of the original bulk crystal. A combination of such wave-guides with a line-defect wave-guide is shown to have desirable characteristics for filtered wave-guides and wave-couplers.

Manipulation of negative-index collimation beam using band-gap guidance

2018 ◽  
Vol 82 (1) ◽  
pp. 10401
Author(s):  
Fengfu Shen ◽  
Ge Zhu ◽  
Qing Shi ◽  
Zengtao Lv
Keyword(s):  
Integrated Circuits ◽  
Band Gap ◽  
Acoustic Waves ◽  
Resonant Mode ◽  
Negative Index ◽  
First Order ◽  
Directional Emission ◽  
Source Distance ◽  
Potential Applications ◽  
Sonic Crystal

We manipulate the source distance, emission position and number of negative-index collimation beam in a two-dimensional hybrid sonic crystal by using band-gap waveguide to control the flow of acoustic waves from a point source. The desired beam manipulations can be achieved at many different frequencies by suitably selecting the first order resonant mode of two crystal components and the waveguide structures. These results have potential applications in acoustic mutifunctional directional emission and acoustic integrated circuits. The proposed approach is also applicable for the similar manipulations of other types of acoustic collimation beams.

scholarly journals From Time-Collocated to Leapfrog Fundamental Schemes for ADI and CDI FDTD Methods

Axioms ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 23
Author(s):  
Eng Leong Tan
Keyword(s):  
Finite Difference ◽  
Time Domain ◽  
Finite Difference Time Domain ◽  
Fdtd Method ◽  
Unconditionally Stable ◽  
Alternating Direction Implicit ◽  
One Dimensional ◽  
Alternating Direction ◽  
Fdtd Methods ◽  
Difference Time

The leapfrog schemes have been developed for unconditionally stable alternating-direction implicit (ADI) finite-difference time-domain (FDTD) method, and recently the complying-divergence implicit (CDI) FDTD method. In this paper, the formulations from time-collocated to leapfrog fundamental schemes are presented for ADI and CDI FDTD methods. For the ADI FDTD method, the time-collocated fundamental schemes are implemented using implicit E-E and E-H update procedures, which comprise simple and concise right-hand sides (RHS) in their update equations. From the fundamental implicit E-H scheme, the leapfrog ADI FDTD method is formulated in conventional form, whose RHS are simplified into the leapfrog fundamental scheme with reduced operations and improved efficiency. For the CDI FDTD method, the time-collocated fundamental scheme is presented based on locally one-dimensional (LOD) FDTD method with complying divergence. The formulations from time-collocated to leapfrog schemes are provided, which result in the leapfrog fundamental scheme for CDI FDTD method. Based on their fundamental forms, further insights are given into the relations of leapfrog fundamental schemes for ADI and CDI FDTD methods. The time-collocated fundamental schemes require considerably fewer operations than all conventional ADI, LOD and leapfrog ADI FDTD methods, while the leapfrog fundamental schemes for ADI and CDI FDTD methods constitute the most efficient implicit FDTD schemes to date.

scholarly journals Photonic band gap of multiferroic-dielectric materials in the IR region: FDTD method

2019 ◽  
Vol 539 (1) ◽  
pp. 50-54
Author(s):  
Selami Palaz ◽  
Sevket Simsek ◽  
Amirullah M. Mamedov ◽  
Ekmel Ozbay
Keyword(s):  
Band Gap ◽  
Photonic Band Gap ◽  
Fdtd Method ◽  
Dielectric Materials ◽  
Photonic Band

Parametric Study on Rectangular Sonic Crystal

2012 ◽  
Vol 152-154 ◽  
pp. 281-286 ◽  
Author(s):  
Arpan Gupta ◽  
Kian Meng Lim ◽  
Chye Heng Chew
Keyword(s):  
Band Gap ◽  
Periodic Structure ◽  
Parametric Study ◽  
Sound Propagation ◽  
Periodic Structures ◽  
Sound Attenuation ◽  
Experimental Results ◽  
Center Frequency ◽  
Sonic Crystal ◽  
Sonic Crystals

Sonic crystals are periodic structures made of sound hard scatterers which attenuate sound in a range of frequencies. For an infinite periodic structure, this range of frequencies is known as band gap, and is determined by the geometric arrangement of the scatterers. In this paper, a parametric study on rectangular sonic crystal is presented. It is found that geometric spacing between the scatterers in the direction of sound propagation affects the center frequency of the band gap. Reducing the geometric spacing between the scatterers in the direction perpendicular to the sound propagation helps in better sound attenuation. Such rectangular arrangement of scatterers gives better sound attenuation than the regular square arrangement of scatterers. The model for parametric study is also supported by some experimental results.

Design and Numerical Analysis of an All-optical 4-channel Power Splitter in E, S, C, L, and U Bands via Nano-line Defects in Photonic Crystal

2020 ◽  
Vol 41 (3) ◽  
pp. 241-247
Author(s):  
Saeed Olyaee ◽  
Mahmood Seifouri ◽  
Ebrahim Azimi Sourani ◽  
Vigneswaran Dhasarathan
Keyword(s):  
Photonic Crystal ◽  
Band Gap ◽  
Output Power ◽  
Wavelength Range ◽  
Fdtd Method ◽  
Input Power ◽  
Square Lattice ◽  
Power Splitter ◽  
All Optical ◽  
Line Defects

AbstractIn the present study, the propagation of electromagnetic waves in a square-lattice photonic crystal waveguide (PCW) is investigated using the finite-difference time-domain (FDTD) method. Then, the plane wave expansion (PWE) method is utilized to calculate the 2D photonic crystal band structure. To realize the desired waveguide, nano-line defects are introduced. The results of the numerical simulations and optimization scanning indicate that for the proposed photonic crystal structure consisting of silicon circular dielectric rods with a radius of 84 nm, a band gap can be achieved in the wavelength range of 1.34 μm<λ<1.93 μm. This wavelength range covers E, S, C, L, and U communication bands. Subsequently, by eliminating the rods in four parts of the structure, an all-optical 4-channel splitter can be designed. The numerical simulation results indicate that by coupling a light source to the main path of the structure and propagating it through each channel, the powers of the 4 output facets become approximately the same. The output power of channels 1 and 2 equals to 24.5 % of the input power, and the output power of channels 3 and 4 is 21 % of the input power and the remaining 9 % is lost in the structure as the leakage power. Since the 1.55 μm wavelength is within the band gap, that is the telecommunication band C, this device can be used as a power splitter.

Analysis and Measurement of Wave Guides Using Poisson Method

2017 ◽  
Vol 8 (2) ◽  
pp. 546
Author(s):  
M. Sudha ◽  
A. Kumaravel
Keyword(s):  
Poisson Equation ◽  
Resonant Mode ◽  
Exact Calculation ◽  
Mode Expansion ◽  
The Poisson Equation ◽  
Expansion Technique ◽  
Wave Guides ◽  
Precise Assessment

<p>The Poisson equation is used to analyze and measure the waveguide in quick and exact calculation of Green's capacity. For this reason, Green's capacity is composed as far as Jacobian elliptic capacities including complex contentions. Another calculation for the quick and precise assessment of such Green's capacity is definite. The principle advantage of this calculation is effectively appeared inside the casing of the Limit Integral Resonant Mode Expansion technique, where a generous decrease of the computational exertion identified with the assessment of the referred to Green's capacity is gotten.</p>

Theoretical and Experimental Study of Locally Resonant and Bragg Band Gaps in Flexural Beams Carrying Periodic Arrays of Beam-Like Resonators

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Yong Xiao ◽  
Jihong Wen ◽  
Gang Wang ◽  
Xisen Wen
Keyword(s):  
Band Gap ◽  
Coupling Effect ◽  
Numerical Study ◽  
Spectral Element ◽  
Band Gaps ◽  
Local Resonance ◽  
Periodic Arrays ◽  
Finite Structures ◽  
Resonance Frequencies ◽  
Vibration Transmittance

In this paper, we present a design of locally resonant (LR) beams using periodic arrays of beam-like resonators (or beam-like vibration absorbers) attached to a thin homogeneous beam. The main purpose of this work is twofold: (i) providing a theoretical characterization of the proposed LR beams, including the band gap behavior of infinite systems and the vibration transmittance of finite structures, and (ii) providing experimental evidence of the associated band gap properties, especially the coexistence of LR and Bragg band gaps, and their evolution with tuned local resonance. For the first purpose, an analytical method based on the spectral element formulations is presented, and then an in-depth numerical study is performed to examine the band gap effects. In particular, explicit formulas are provided to enable an exact calculation of band gaps and an approximate prediction of band gap edges. For the second purpose, we fabricate several LR beam specimens by mounting 16 equally spaced resonators onto a free-free host beam. These specimens use the same host beam, but the resonance frequencies of the resonators on each beam are different. We further measure the vibration transmittances of these specimens, which give evidence of three interesting band gap phenomena: (i) transition between LR and Bragg band gaps; (ii) near-coupling effect of the local resonance and Bragg scattering; and (iii) resonance frequency of local resonators outside of the LR band gap.

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