设计了一种在轴向能够实现焦点延长的双焦点超表面聚焦透镜.改变二氧化钛纳米微元的长宽比和旋转角度，对传输相位与几何相位进行同时调制，实现对一组正交偏振态入射光的分别独立控制.设计的超构表面能将左旋和右旋圆偏振光聚焦在轴向邻近位置实现焦点长度的轴向扩展.超表面在波长为650 nm的线偏入射光照明下，可以在实现焦点长度2倍扩展的同时，较好地保持焦点的横向宽度.若入射光为椭圆偏振态，还能够实现最终生成的焦点形状优化或两个焦点的切换.

A focusing lense with two focal spots based on dielectric metasurface was designed which can extend the focus axially. The device modulates the propagation phase and the geometric phase at the same time and realizes the independent control of a group of orthogonal polarized incident light by varying the aspect ratio and the rotation angle of the titanium dioxide pillars. The designed metasurface focuses the left-handed and right-handed circularly polarized light at contiguous positions to extend the focus axially. We extend the length of focus twice as initial value at 650 nm wavelength and maintain the lateral width of the focus in the meantime. The optimization of the focus shape and the switch of focus position with different focal lengths can be realized by adjusting the incident light into an elliptically polarized light.