Near-diffraction-limited F-3.1 apochromat singlet lens design enabled by spherical gradient index

Abstract This paper presents a numerical study on multi-mode focusing of guided elastic waves in pipe-like structures over a range of frequencies using a single metamaterial lens design. We explore focusing of the first two longitudinal (L(0,1) and L(0,2)) and the first torsional (T(0,1)) wave modes in steel pipe integrated with a metamaterial lens made of cylindrical steel stubs of varying heights attached to outer surface of the pipe. Proposed metamaterial lens design is based on gradient index (GRIN) theory with hyperbolic secant distribution of refractive index in circumferential direction. Amplification of multi-mode guided wave signals are achieved at focal points of the lens which is verified through numerical simulations. The focusing performance of proposed lens is studied at multiple frequencies for all the three modes and first two focal positions are verified with theoretical predictions of GRIN theory.

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Acoustic gradient index lens design using gradient based optimization

The Journal of the Acoustical Society of America ◽

10.1121/1.5036383 ◽

2018 ◽

Vol 143 (3) ◽

pp. 1948-1948 ◽

Cited By ~ 2

Author(s):

Feruza Amirkulova ◽

Samuel T. Caton ◽

Morgan Schrader ◽

Trenton J. Gobel ◽

Andrew Norris

Keyword(s):

Lens Design ◽

Gradient Index ◽

Gradient Based ◽

Gradient Index Lens

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Advancements in transformation optics-enabled gradient-index lens design

10.1117/12.2187513 ◽

2015 ◽

Author(s):

Sawyer D. Campbell ◽

Donovan E. Brocker ◽

Jogender Nagar ◽

John A. Easum ◽

Douglas H. Werner ◽

...

Keyword(s):

Transformation Optics ◽

Lens Design ◽

Gradient Index ◽

Gradient Index Lens

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Transformation optics-inspired dispersion-corrected gradient-index lens design

2016 IEEE International Symposium on Antennas and Propagation (APSURSI) ◽

10.1109/aps.2016.7696681 ◽

2016 ◽

Author(s):

Donovan E. Brocker ◽

Sawyer D. Campbell ◽

Jogender Nagar ◽

Douglas H. Werner

Keyword(s):

Transformation Optics ◽

Lens Design ◽

Gradient Index ◽

Gradient Index Lens

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Enhanced Sound Energy Harvesting by Leveraging Gradient-Index Phononic Crystals

ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems ◽

10.1115/smasis2020-2411 ◽

2020 ◽

Author(s):

Ahmed Allam ◽

Karim Sabra ◽

Alper Erturk

Keyword(s):

Finite Element ◽

Numerical Simulations ◽

Acoustic Waves ◽

Design Procedure ◽

Unit Cell ◽

Design Parameters ◽

Lens Design ◽

Gradient Index ◽

Cell Design ◽

Electrical Load

Abstract We explore the harvesting of acoustic waves by leveraging a 3D-printed gradient-index phononic crystal (GRIN-PC) lens design. The concept is demonstrated numerically and experimentally for audio frequency range acoustic waves in air. Unit cell design procedure to achieve the required refractive index profile and numerical simulations of the band structure are executed using a high-fidelity finite-element model, followed by 3D simulations of the acoustic wave field for validation of the lens performance. Performance enhancement by focusing acoustic waves is quantified along with the level of anisotropy in the resulting 3D lens design. Additionally, a fully coupled multiphysics framework is developed to cover acoustic-structure interaction, piezoelectric coupling, as well as electrical load impedance. Finite-element simulations include the GRIN-PC lens and the harvester components along with basic electrical load to quantify the electrical power. In the full numerical simulations, design parameters such as the unit cell design, aperture of the lens, directional effects and anisotropy are explored in detail. Specifically, efforts are summarized on the unit cell design to minimize the directional sensitivity, toward making the lens close to omnidirectional.

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