Design of mid-infrared dielectric metasurface based on cross-like meta-atom

Abstract Mid-infrared (MIR) optics plays an important role in medical, military and scientific research fields. However, the expensive material costs and complicated processing techniques hinder the convention MIR optics from more commercial uses. Due to the excellent ability to control electromagnetic wave and a low fabrication cost, metasurfaces provide a promising solution to the challenges in MIR optics. In this paper, we propose a cross-like silicon meta-atom working at the MIR waveband. In the simulation, we use the proposed meta-atom to design a polarization-dependent beam deflector, a polarization-independent metalens and polarization-dependent bifocal metalenses respectively. The beam deflector diffracts the incident circularly polarized light to the desired direction. The diffraction efficiency and signal-to-noise ratio reach 93.4% and 16.72 dB respectively at the wavelength of 4. 8 μ m . The polarization-independent metalens demonstrates the same focal length for the different linearly polarized light, and maintains the sub-wavelength convergence characteristics among 4.6-5. 0 μ m . The bifocal metalens focuses the different linearly polarized light to the different focal points with the sub-wavelength convergence characteristics. The simulation results show that our design enables high-efficiency, ultra-lightweight and dielectric MIR optics.