Widespread attention has been paid to the achromatic metalens recently. However,there are still obstacles in the design of achromatic metalens to simultaneously satisfy the required focus phase,group delay,and group delay dispersion. Therefore,vanadium dioxide (VO2),a phase change material,was used to provide a new degree of freedom for designing the terahertz achromatic metalens. Here a method was presented for reconfigurable terahertz achromatic metalens based on VO2 . Different Pancharatnam-Berry phases can be introduced by switching VO2 between the insulating and metallic states. Thus,the metalens can satisfy the phase profile of the metalens required for different frequencies and realize achromatic characteristics. For verification,a dual-frequency reconfigurable achromatic metalens was designed working at 1.93 THz and 2.14 THz. A single-frequency non-reconfigurable metalens was designed working at 1.93 THz for comparison. The simulation results show that the designed reconfigurable metalens can effectively reduce the focus length shift. Therefore,the metalens has achromatic characteristics.
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