  Compact and miniaturized devices with flexible functionalities are always
highly demanded in optical integrated systems. Plasmonic nanosieve has been
successfully harnessed as an ultrathin flat platform for complex manipulation
of light, including holography, vortex generation and non-linear processes.
Compared with most of reported single-functional devices, multi-functional
nanosieves might find more complex and novel applications across
nano-photonics, optics and nanotechnology. Here, we experimentally demonstrate
a promising roadmap for nanosieve-based helical devices, which achieves full
manipulations of optical vortices, including its generation, hybridization,
spatial multiplexing, focusing and non-diffraction propagation etc., by
controlling the geometric phase of spin light via over 121 thousands of
spatially-rotated nano-sieves. Thanks to such spin-conversion nanosieve helical
elements, it is no longer necessary to employ the conventional two-beam
interferometric measurement to characterize optical vortices, while the
interference can be realized natively without changing any parts of the current
setup. The proposed strategy makes the far-field manipulations of optical
orbital angular momentum within an ultrathin interface viable and bridges
singular optics and integrated optics. In addition, it enables more unique
extensibility and flexibility in versatile optical elements than traditional
phase-accumulated helical optical devices.

Optics