In this paper, we propose an anisotropic dual-band phase gradient metasurface in the infrared region based on tellurium material, which exhibits strong birefringence for z-cut. The refractive index of ordinary light no and extraordinary light ne are along the x- and y-direction of the metasurface, respectively. When a plane wave polarized along the x-direction is normally incident on the metasurface, the diffraction efficiency, which is defined as power of the deflected beam in the desired +1 diffraction order normalized to total transmission power, keeps higher than 95% within the wavelength from 7140nm to 7260nm, meanwhile the total transmission efficiency remains above 78%. On the other hand, the diffraction and total transmission efficiencies keep higher than 95% and 65% within wavelength range from 7840nm to 7940nm for the y-polarized illumination. The metasurface can be applied into polarization splitter, spectral beam splitter, and more in the future.

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Jing Li, Chang Liu, Yumin Liu, Yu Wang, Zhongyuan Yu, Han Ye, and Li Yu, "High efficiency anisotropic dual-band metasurface in the infrared region," Proc. SPIE 10928, High Contrast Metastructures VIII, 109281J (Presented at SPIE OPTO: February 07, 2019; Published: 4 March 2019); https://doi.org/10.1117/12.2507698.