Design of achromatic metalens based on dielectric metasurface

Metalenses based on all-dielectric metasurfaces plays an important role in microscopic imaging, machine vision and holographic imaging. Chromatic aberration correction is an important factor that imaging devices. In this work, we propose an transmission achromatic metalens that can operate over a broad band of wavelengths. Based on the principle of phase compensation, the finite-difference time-domain method is used to calculate the wavefront of light for the design of the nano-units in the metalens with eliminating chromatic aberration. In the whole incident spectrum of visible light from 425 nm to 625 nm, The maximum focal shift of the achromatic metalens is about 7.9 %.And the average efficiency of the metalens with a numerical aperture of 0.6 is about 42 % in the wavelength band.