  Electromagnetic waves carrying orbital angular momentum (OAM) have found many
applications. This work reports a broadband millimeter wave OAM generator
applying a dielectric metasurface with high-refractive-index dielectric
elements distributed on a low-refractive-index substrate. Proper adjustment of
the dimensions of the dielectric elements can make a broadband OAM generator
from 53 to 70 GHz. OAM generators with different mode numbers are designed and
validated by simulation. Such structures can find potential applications in
high-capacity communications and imaging.
