Terahertz metasurface zone plates with arbitrary polarizations to a fixed polarization conversion
A new publication from Opto-Electronic Advances; DOI 10.29026/oes.2022.210014 overviews terahertz metasurface zone plates with arbitrary polarizations to a fixed polarization conversion.
As an inherent property of electromagnetic waves, polarization has a wide range of applications in information processing, quantum optics, and polarization imaging. For traditional optical devices, converting unpolarized light into specific polarized light relies on the combination of linear polarizers and other polarizing devices, which undoubtedly increases the size of the optical device. The proposed chiral metasurface effectively reduce the size of the polarizing device. Chiral metasurfaces have different responses to orthogonal circularly polarized waves. Taking a transmissive metasurface as an example, when the incident light wave is in the state of left-handed circular polarization, the metasurface can generate transmitted right-handed circularly polarized (RCP) waves; when the incident light wave is RCP, the metasurface hardly produces transmission wave. For unpolarized incident waves, the chiral metasurface can generate specific circularly polarized waves.
In addition, linearly polarized (LP) waves also play an important role in high-resolution imaging. For example, by independently adjusting the orientation angle of each nanorod, nearly arbitrary intensity manipulation of LP beam could be obtained, providing another option for imaging or encoding information. Therefore, metasurfaces that can control the wavefront while realizing polarization manipulation can further advance the development of polarization devices.
This work proposes a scheme to achieve arbitrary polarization to fixed polarization conversion via a metasurface zone plate. For metasurface zone plates, the odd-numbered and even-numbered ring zones are composed of different meta-atoms and the total number of rings is even. Then, once one polarized beam is incident, the outgoing waves in response to the odd-numbered and the even-numbered ring zones are focused on the same point and superimposed to engender a fixed polarized wave.
To demonstrate the feasibility of the scheme, this work demonstrates two polarization devices. The first polarizer is a linear polarizer. Under the incidence of various types of polarized waves, the metasurface zone plate can always generate focused LP waves. The second device is a circular polarizer. When the polarization states of the incident wave are linear, circular, and elliptical, the transmitted wave will be focused at a distance of 1.7 cm away from the metasurface zone plate, and the wave of the focal plane is the RCP wave.
The simulated and measured results are consistent with the theoretical expectations, verifying that the proposed concept is flexible and feasible. The strategy can effectively reduce the fabrication difficulty of polarizing devices and may improve the versatility and integration of optical devices.
Article reference Yue Z, Li JT, Li J, Zheng CL, Liu JY et al. Terahertz metasurface zone plates with arbitrary polarizations to a fixed polarization conversion. Opto-Electron Sci 1, 210014 (2022). doi: 10.29026/oes.2022.210014
Keywords: metasurface zone plates / polarization / conversion / terahertz
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Professor Jianquan Yao, academician of Chinese Academy of Sciences, is working at Tianjin University, China. The group of Professor Yao is mainly engaged in theoretical and applied research in nonlinear optics, laser technology, optical communication, terahertz science and technology, etc. This group is supported by more than 30 projects including National Natural Science Foundation of China, National Key Research and Development Program of China, etc. Professor Yao has won National Invention Award of China, and the Grand Prize of the Chinese Academy of Sciences. To date, he has published 700+ papers, and 20+ invention patents. http://laser.tju.edu.cn/index.htm
Professor Yan Zhang, Fellow of the Optical Society of America, is working at Capital Normal University, China. He is also supported by Program for New Century Excellent Talents in University, China. He has successively engaged in research work at Yamagata University in Japan, Hong Kong Polytechnic University, University of Stuttgart in Germany, Hong Kong University of Science and Technology, Leinster University of Technology in the United States, and University of Konstanz in Germany. Currently, the group of Professor Zhang is mainly engaged in research on terahertz optoelectronics, micro-nano optics, optical information processing, etc., and has published more than 270 journal papers in Nature Photonics, Nature Communications, Advance Optical Materials, etc.
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