Numerical design of a dual-wavelength confocal metalens with photonic crystal filter based on filter-substrate-metasurface structure

In this paper, a novel type of dual-wavelength confocal metalens is proposed from the perspective of structural design, in order to solve the spatial crosstalk between two wavelengths. With the function of filter-substratemetasurface (FSM) structure based on photonic crystal filtering, we designed a miniaturized dual-wavelength confocal metalens with a radius of 36 mu m and a focal length of 91 mu m. The results of our work show that it can greatly reduce the spatial crosstalk between any two wavelengths, and complete confocal with high precision without reducing the focusing efficiency, so that the focus difference between the two wavelengths of light is less than 1 mu m. Besides, through simulation we also found that the lens can focus light in the bandwidths around these two wavelengths (1.33-1.38 mu m and 1.50-1.55 mu m), but also maintain a good focusing efficiency. Therefore, the proposed metalens can be used to realize imaging, microscopy, high-speed and efficient optical fiber communication and many related fields.