Achromatic polarization-multiplexed varifocal metalens with a broad bandwidth

A polarization-multiplexed imaging system that utilises metasurfaces as its design effectively addresses the issue of the conventional imaging system's cumbersome size. However, their inability to function at broad wavelength due to the presence of chromatic aberration. An achromatic polarization-multiplexed varifocal metalens with a broad bandwidth (APVM) is illustrated in this paper. By utilising a particle swarm optimization algorithm, we have significantly diminished the phase compensation matching error in the achromatic scheme. Simulation results show that the design can effectively suppress the chromatic aberration at 610-740 nm wavelengths and change the focal length according to the polarization. Furthermore, functioning as an achromatic polarization-multiplexed metalens, demonstrates an exceptional average focusing efficiency of 49.7 % and nearly diffraction-limited focusing across the operational wavelengths. It is anticipated that this design will find widespread applications in the fields of medical imaging, target detection and optical communications.