Unconventional, efficient and flexible bifocal lens design by metalens and AFA beam combination

In the field of metasurface-based light focusing, both convex metalenses with parabolic phase profile and autofocused Airy (AFA) beams play essential roles. AFA beam generation as a combination of two convergent mirrored Airy beams leaves the space between the two launched Airy profiles inefficient with zero amplitude transmission and constant phase distribution. In this paper, we propose using this inutile space as an independent metalens. We show that coincidence of the focal spot of the metalens to that of the AFA beam will increase the focusing intensity more than 24 percent at its focal point. It is shown that using the nonoperative space between the two launched Airy beams as an independent metalens not only does not disrupt the AFA focusing efficiency, but also enables us to use the full potential of the space to increase the focusing efficiency or flexibly assigning the focusing spots.