Modified structural Luneburg lens for broadband focusing and collimation
Luneburg lens is a symmetric gradient-index lens with a refractive index that increases from the outer surface to the center in a radial manner. It has the ability to focus and collimate waves, which makes it useful for energy harvesting, waveguiding and as a component in transducers. An ideal Luneb...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/146666 |
| _version_ | 1824456143021277184 |
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| author | Zhao, Liuxian Lai, Chang Quan Yu, Miao |
| author2 | Temasek Laboratories @ NTU |
| author_facet | Temasek Laboratories @ NTU Zhao, Liuxian Lai, Chang Quan Yu, Miao |
| author_sort | Zhao, Liuxian |
| collection | NTU |
| description | Luneburg lens is a symmetric gradient-index lens with a refractive index that increases from the outer surface to the center in a radial manner. It has the ability to focus and collimate waves, which makes it useful for energy harvesting, waveguiding and as a component in transducers. An ideal Luneburg lens should be easy to fabricate, has broadband and omnidirectional characteristics, as well as a focal length that can be easily tuned. However, existing structural Luneburg lenses based on phononic crystals can hardly achieve these requirements. Here, we propose an alternative structural Luneburg lens which has a refractive index that varies smoothly with its radial distance as a result of a changing thickness. Theoretical calculations, numerical simulations and experimental measurements of flexural wave propagation through the lens showed that flexural wave focusing can be obtained inside, at the edge and outside of the variable thickness lens for different frequencies and propagation directions. Flexural wave collimation was also demonstrated when a point source was placed at the respective focal points for each lens. Furthermore, it was shown that flexural waves that were focused onto a piezoelectric energy harvester by the Luneburg lens can lead to a significant increase in the harvested voltage compared to that obtained without focusing. |
| first_indexed | 2025-02-19T03:49:24Z |
| format | Journal Article |
| id | ntu-10356/146666 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2025-02-19T03:49:24Z |
| publishDate | 2021 |
| record_format | dspace |
| spelling | ntu-10356/1466662021-03-06T20:12:11Z Modified structural Luneburg lens for broadband focusing and collimation Zhao, Liuxian Lai, Chang Quan Yu, Miao Temasek Laboratories @ NTU Science::Physics::Acoustics Variable Thickness Structure Modified Structural Luneburg Lens Luneburg lens is a symmetric gradient-index lens with a refractive index that increases from the outer surface to the center in a radial manner. It has the ability to focus and collimate waves, which makes it useful for energy harvesting, waveguiding and as a component in transducers. An ideal Luneburg lens should be easy to fabricate, has broadband and omnidirectional characteristics, as well as a focal length that can be easily tuned. However, existing structural Luneburg lenses based on phononic crystals can hardly achieve these requirements. Here, we propose an alternative structural Luneburg lens which has a refractive index that varies smoothly with its radial distance as a result of a changing thickness. Theoretical calculations, numerical simulations and experimental measurements of flexural wave propagation through the lens showed that flexural wave focusing can be obtained inside, at the edge and outside of the variable thickness lens for different frequencies and propagation directions. Flexural wave collimation was also demonstrated when a point source was placed at the respective focal points for each lens. Furthermore, it was shown that flexural waves that were focused onto a piezoelectric energy harvester by the Luneburg lens can lead to a significant increase in the harvested voltage compared to that obtained without focusing. Accepted version 2021-03-04T07:04:51Z 2021-03-04T07:04:51Z 2020 Journal Article Zhao, L., Lai, C. Q., & Yu, M. (2020). Modified structural Luneburg lens for broadband focusing and collimation. Mechanical Systems and Signal Processing, 144, 106868-. doi:10.1016/j.ymssp.2020.106868 0888-3270 https://hdl.handle.net/10356/146666 10.1016/j.ymssp.2020.106868 144 106868 en Mechanical Systems and Signal Processing © 2020 Elsevier Ltd. All rights reserved. This paper was published in Mechanical Systems and Signal Processing and is made available with permission of Elsevier Ltd. application/pdf |
| spellingShingle | Science::Physics::Acoustics Variable Thickness Structure Modified Structural Luneburg Lens Zhao, Liuxian Lai, Chang Quan Yu, Miao Modified structural Luneburg lens for broadband focusing and collimation |
| title | Modified structural Luneburg lens for broadband focusing and collimation |
| title_full | Modified structural Luneburg lens for broadband focusing and collimation |
| title_fullStr | Modified structural Luneburg lens for broadband focusing and collimation |
| title_full_unstemmed | Modified structural Luneburg lens for broadband focusing and collimation |
| title_short | Modified structural Luneburg lens for broadband focusing and collimation |
| title_sort | modified structural luneburg lens for broadband focusing and collimation |
| topic | Science::Physics::Acoustics Variable Thickness Structure Modified Structural Luneburg Lens |
| url | https://hdl.handle.net/10356/146666 |
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