Multifocal co-plane metalens based on computer-generated holography for multiple visible wavelengths

Traditional optical components need to accumulate optical path to control the wavefront. To achieve a desired function, several components are cascaded resulting in optical systems that are bulky and costly. In recent years, metasurfaces have attracted increasing attention because of the capability to manipulate the phase, polarization, and amplitude of electromagnetic waves at the subwavelength scale. In this work, a kind of broadband single focal and multifocal metalenses based on computer-generated holography in the visible light was designed. The phase distribution and metalens structure of the multifocal metalenses are designed by the method of computer - generated holography. The designed antenna units were arranged according to the phase distribution, and square single focal metalens and multifocal metalenses were obtained. Besides, at the designed wavelength of 612 nm, metalens exhibits a high focusing efficiency, which is about 15% higher than the previous method. The broadband performance of the metalenses and the multi -region confocal metalens also been discussed, which also achieved good focusing effects and broke the optical diffraction limit. This work may find itself significant applications in optical tomography techniques, optical data storage, and so on.