Imaging performance of a mid-infrared metalens with a machining error.

Metalenses exhibit excellent performance as a new type of optical element; mid-infrared devices based on metalenses are advantageous to numerous applications in biomedical, military and industrial fields. The demand for large-area and high-efficiency mid-infrared metalenses has increased in recent years. However, the current processing methods for metalens production introduce different types of processing errors. Therefore, qualitative analyses of various errors that may exist in the processing of metalenses should be performed. In this study, we use the finite-difference time-domain calculation method and introduce various typical errors into a transmission phase-based mid-infrared metalens for simulation and analysis. The simulation results show that the defects caused by these processes affect focusing efficiency, and that some defects affect the quality of light. Subsequently, we prepare a metalens within the allowable error range and test its optical performances. The experiment confirms the excellent imaging performance of our metalens. Our study can help manufacturers identify defects to improve manufacturing processes, thereby enabling the incorporation of metalenses in industrial applications.