Doped metasurfaces: Etched structure-free flims based on regular spatially doped semiconductor and compatible with general optical ones.

The metasurfaces through the reasonable design and arrangement of subwavelength nanostructures to control the spatial light field are expected to replace the traditional lens elements. However, the low light use efficiency (LUE) and difficulty in preparation caused by the etching process restrict the development of its application. Here, an idea of "doped metasurfaces" based on a spatial and regular doping of semiconductor thin films is proposed for the first time. Since the metasurfaces has no etched micro-nano structure, other optical functional films are allowed to be added, which greatly improves and enriches its optical performance. The effectiveness of the design is verified by simulating a suitable metasurface lens. The simulation results show that this designed MIR metalens possesses wide operating range, high transmittance, and high LUE. The method proposed here provides a new idea or perspective for constructing metasurfaces devices compatible with traditional optical thin films.