Broadband Ultra-Deep Sub-Diffraction-Limit Optical Focusing by Metallic Graded-Index (MGRIN) Lenses
The development of techniques for efficiently confining energy in the visible and infrared spectral regions to the deep subwavelength spatial scale with dimensions as small as a few nanometers would have great significance for scientific research and engineering practices. Such an ability to manipul...
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| Format: | Article |
| Language: | English |
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MDPI AG
2017-08-01
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| Series: | Nanomaterials |
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| Online Access: | https://www.mdpi.com/2079-4991/7/8/221 |
| _version_ | 1819036826514489344 |
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| author | Yechuan Zhu Weizheng Yuan Hao Sun Yiting Yu |
| author_facet | Yechuan Zhu Weizheng Yuan Hao Sun Yiting Yu |
| author_sort | Yechuan Zhu |
| collection | DOAJ |
| description | The development of techniques for efficiently confining energy in the visible and infrared spectral regions to the deep subwavelength spatial scale with dimensions as small as a few nanometers would have great significance for scientific research and engineering practices. Such an ability to manipulate light is impossible for conventional dielectric lenses due to the diffraction limit. Here, we propose a metallic graded-index (MGRIN) lens formed by an array of coupled metallic waveguides with identical nanoscale widths embedded by index-varying dielectrics to enable the optical nanofocusing. The focusing mechanism of the MGRIN lens is theoretically investigated based on Hamiltonian optics, which are verified by the finite-difference time-domain (FDTD) method. Numerical results reveal that an ultra-deep subwavelength focus of 8 nm (λ/500) with a long focal depth (1.93λ) and enhanced field intensity can be achieved. Moreover, the nanofocusing capability of the MGRIN lens without redesigning the structure can be well kept when the incident wavelength changes over a broad range from visible to infrared. Our design of optical nanofocusing shows great potential for use in nano-optics and nanotechnology. |
| first_indexed | 2024-12-21T08:11:42Z |
| format | Article |
| id | doaj.art-b8e19c26e78741edb9efacb5ceb15e86 |
| institution | Directory Open Access Journal |
| issn | 2079-4991 |
| language | English |
| last_indexed | 2024-12-21T08:11:42Z |
| publishDate | 2017-08-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Nanomaterials |
| spelling | doaj.art-b8e19c26e78741edb9efacb5ceb15e862022-12-21T19:10:39ZengMDPI AGNanomaterials2079-49912017-08-017822110.3390/nano7080221nano7080221Broadband Ultra-Deep Sub-Diffraction-Limit Optical Focusing by Metallic Graded-Index (MGRIN) LensesYechuan Zhu0Weizheng Yuan1Hao Sun2Yiting Yu3Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Xi’an 710072, ChinaKey Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Xi’an 710072, ChinaKey Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Xi’an 710072, ChinaKey Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Xi’an 710072, ChinaThe development of techniques for efficiently confining energy in the visible and infrared spectral regions to the deep subwavelength spatial scale with dimensions as small as a few nanometers would have great significance for scientific research and engineering practices. Such an ability to manipulate light is impossible for conventional dielectric lenses due to the diffraction limit. Here, we propose a metallic graded-index (MGRIN) lens formed by an array of coupled metallic waveguides with identical nanoscale widths embedded by index-varying dielectrics to enable the optical nanofocusing. The focusing mechanism of the MGRIN lens is theoretically investigated based on Hamiltonian optics, which are verified by the finite-difference time-domain (FDTD) method. Numerical results reveal that an ultra-deep subwavelength focus of 8 nm (λ/500) with a long focal depth (1.93λ) and enhanced field intensity can be achieved. Moreover, the nanofocusing capability of the MGRIN lens without redesigning the structure can be well kept when the incident wavelength changes over a broad range from visible to infrared. Our design of optical nanofocusing shows great potential for use in nano-optics and nanotechnology.https://www.mdpi.com/2079-4991/7/8/221nanofocusingcoupled metallic waveguidesmetallic graded-index lensHamiltonian optics |
| spellingShingle | Yechuan Zhu Weizheng Yuan Hao Sun Yiting Yu Broadband Ultra-Deep Sub-Diffraction-Limit Optical Focusing by Metallic Graded-Index (MGRIN) Lenses Nanomaterials nanofocusing coupled metallic waveguides metallic graded-index lens Hamiltonian optics |
| title | Broadband Ultra-Deep Sub-Diffraction-Limit Optical Focusing by Metallic Graded-Index (MGRIN) Lenses |
| title_full | Broadband Ultra-Deep Sub-Diffraction-Limit Optical Focusing by Metallic Graded-Index (MGRIN) Lenses |
| title_fullStr | Broadband Ultra-Deep Sub-Diffraction-Limit Optical Focusing by Metallic Graded-Index (MGRIN) Lenses |
| title_full_unstemmed | Broadband Ultra-Deep Sub-Diffraction-Limit Optical Focusing by Metallic Graded-Index (MGRIN) Lenses |
| title_short | Broadband Ultra-Deep Sub-Diffraction-Limit Optical Focusing by Metallic Graded-Index (MGRIN) Lenses |
| title_sort | broadband ultra deep sub diffraction limit optical focusing by metallic graded index mgrin lenses |
| topic | nanofocusing coupled metallic waveguides metallic graded-index lens Hamiltonian optics |
| url | https://www.mdpi.com/2079-4991/7/8/221 |
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