**4. Conclusions**

In conclusion, two polarization conversion metasurfaces generating four different orders of OAM carrying beams (*l* = +1, *l* = +2, *l* = −1 and *l* = −2) were designed and fabricated. The simulation and measurement results are in good agreemen<sup>t</sup> with each other. The multi-layered unit cells we proposed realize full phase control, low transmission loss, high polarization conversion efficiency and can be easily tuned to any frequencies of interest. By manipulating the transmission phase distributions on the metasurface aperture, the transmitted beams can carry OAM of four different orders, which has potentials for super resolution imaging. In addition, the polarizations of the transmitted waves were efficiently converted, which may further enhance the performances in applications, for example, imaging polarization dependent objects.

**Author Contributions:** Conceptualization, H.S.; methodology, H.S. and L.W.; validation, H.S.; formal analysis, H.S. and L.W.; investigation, L.W. and M.Z.; resources, A.Z.; data curation, L.W.; writing—review and editing, H.S.; visualization, H.S. and L.W.; supervision, H.S. and J.C.; project administration, J.C., A.Z. and Z.X.; funding acquisition, H.S.

**Funding:** This research was funded by National Natural Science Foundation of China gran<sup>t</sup> number 61871315, in part by Technology Program of Shenzhen gran<sup>t</sup> number JCYJ20170816100722642, in part by the Natural Science Foundation of Guangdong Province, China gran<sup>t</sup> number 2018A030313429 and in part by the China Postdoctoral Science Foundation under Grant 2015M580849. The APC was funded by 61871315.

**Conflicts of Interest:** The authors declare no conflict of interest.
