Broadband acoustic metalens with high transmission높은 투과율을 가지는 광대역 음향 메타렌즈

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In this paper, we propose a broadband acoustic metalens with high transmission for three-dimensional focusing. The lens can be realized by arranging several unit structures with the desired refractive indices. Each unit structure is obtained by rotating about a specific axis a two-dimensional structure designed to have high transmittance and desired refractive index. The two-dimensional structure is a space-coiled structure which is composed of channels with gradually narrowing and then widening widths. By adjusting the coiled length, the refractive index of the structure can be manipulated, and due to the gradual change of the channel width, all structures have broadband high transmission. Then, the two-dimensional structures are modified by an optimization process, so that the two-dimensional axisymmetric structures obtained by rotation have high transmittance and desired refractive indices. The transmittance of the designed two-dimensional axisymmetric unit structures and the focusing performance of the lens are numerically investigated. All unit structures have transmittance higher than 0.8 at about 81% bandwidth of a center frequency 6 kHz, and the sound waves are focused on a very narrow region with a full width at half maximum of 0.44$\lambda$/NA by the lens at 6 kHz, and the acoustic intensity is amplified 23.57 times. ($\lambda$ is the wavelength and NA is the numerical aperture). Finally, the effects of visco-thermal losses and elastic deformation of the lens on the focusing performance are investigated. Under the consideration of the visco-thermal losses, the transmittance of the lens is decreased, but the transmittance is maintained higher than 0.77 in the frequency range of 4 to 8 kHz and the elastic deformation hardly affects the performance of the metalens.
Advisors
Jeon, Wonjuresearcher전원주researcher
Description
한국과학기술원 :기계공학과,
Publisher
한국과학기술원
Issue Date
2020
Identifier
325007
Language
eng
Description

학위논문(석사) - 한국과학기술원 : 기계공학과, 2020.2,[iv, 30 p. :]

Keywords

Acoustic lens▼aMetalens▼aMetasurfaces▼aSpace-coiling structure▼aDesign optimization; 음향 렌즈▼a메타렌즈▼a메타표면▼a꼬인 구조▼a설계 최적화

URI
http://hdl.handle.net/10203/283791
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=901522&flag=dissertation
Appears in Collection
ME-Theses_Master(석사논문)
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