  Manipulating the polarization of light is highly desired for versatile
applications ranging from super resolution, optical trapping, to particle
acceleration. The enormous freedom in metasurface design motivates the
implementation of polarization control in ultrathin and compact optical
systems. However, the majority of proposed strategies based on metasurfaces
have been demonstrated only a spatially homogeneous polarization generation,
while less attention has been devoted to spatially variant inhomogeneous vector
beams. Here, we demonstrate a novel method for generating arbitrary radial and
azimuthal polarization beams with high efficiencies of up to 80% by utilizing
transmission-type dielectric metasurfaces. Polarization conversion metasurfaces
are suitable candidates for the implementation of polarization encryption,
which we demonstrate by encoding a hidden image into the spatial polarization
distribution. In addition, we show that the image pattern can be modified by
appropriate polarization selection of the transmitted light. Such a method may
provide a practical technique for a variety of applications such as imaging,
encryption and anti-counterfeiting.
