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• Chinese Optics Letters
• Vol. 19, Issue 4, 042602 (2021)
Qiangshi Shi1、2, Xia Jin1, Yangyang Fu3, Qiannan Wu4, Cheng Huang1, Baoyin Sun2、*, Lei Gao2, and Yadong Xu2、**
Author Affiliations
• 1College of Energy, Soochow University, Suzhou 215006, China
• 2School of Physical Science and Technology, Soochow University, Suzhou 215006, China
• 3College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
• 4School of Science, North University of China, Taiyuan 030051, China
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Fig. 1. (a) Structure of designed MG-1, a periodic metallic slit array (gray region) filled with two different kinds of media (colored blue regions) alternatively, forming a supercell containing two unit cells (i.e., m = 2). (b) Iso-frequency diagram indicating all possible diffraction orders. (c) and (d) are the magnetic field patterns for incident light with two different incident angles. The working wavelength is $λ=650 nm$.
Fig. 2. (a) Structure of designed MG-2, a periodic metallic slit array (gray region) filled with two different kinds of media (colored blue regions) alternatively, forming a supercell containing two unit cells (i.e., m = 2). (b) Iso-frequency diagram indicating all possible diffraction orders. (c) is the magnetic field patterns for normally incident light.
Fig. 3. Structure of designed bi-layer MG system based on MG-1 and MG-2. (a) and (b) schematically show the scattering process for (a) positive incidence (PI) and (b) negative incidence (NI), respectively.
Fig. 4. (a) When the TM wave is incident to the bi-layer MGs, which are filled with impedance-matched material, the relationship curve between the transmission and reflection efficiency and the size of the air gap for PI and NI, respectively. Magnetic field diagram when the air gap with $Δ=0$ for (b) PI and (c) NI, and magnetic field diagram when the air gap with $Δ=0.25λ$ for (d) PI and (e) NI.
Fig. 5. (a) Geometric structure of nonmagnetic unit cell for the design of magnetic MGs based on the local Fabry–Perot (FP) resonances. (b) Transmission and phase shift of the unit cell versus the height d of filled dielectric with εd$=4$ and μd$=1$. (c) and (d) show the schematic diagram of the redesigned bi-layer MGs for (c) PI and (d) NI, respectively.
Fig. 6. Performance demonstrations. (a) Relationship between the transmission/reflection efficiency and the size of the air gap for PI and NI. (b) Magnetic field pattern for PI when $Δ=580 nm$. (c) Magnetic field pattern for NI when $Δ=580 nm$.
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Qiangshi Shi, Xia Jin, Yangyang Fu, Qiannan Wu, Cheng Huang, Baoyin Sun, Lei Gao, Yadong Xu. Optical beam splitting and asymmetric transmission in bi-layer metagratings[J]. Chinese Optics Letters, 2021, 19(4): 042602