The investigation of height-dependent meta-lens and focusing properties

The advantage of metasurface is to control the phase change artificially and flexibly, which is a very potential research direction. In view of the fact that the dielectric material has less ohmic loss than the metal material and the silicon has superior transmission performance in near infrared band, this work uses the rectangular silicon nano-antenna to analyze and research, and designs an all-dielectric meta-lens with sub-diffraction limitation which works in the transmission mode and adjusts the phase based on the height change. The structure has broadband achromatic property in near infrared region, and its transmission efficiency can be up to 68%. The focal length remains unchanged when.. is from 950 to 1100 nm. By controlling the size of the lens, the effect of the numerical aperture on the focusing performance of the meta-lens is verified. In addition, the bifocal meta-lens is realized by cascading a single structure. It is a new sub-wavelength non-planar structure based on height variation, offering important opportunities for applications in circular polarized optics, fiber sensors, laser scanning fluorescence microscopy, optical signal transmission, and integrated on-chip devices in the future.