  We present and test the integration of a static orbital angular momentum mode
multiplexer with a dynamical geometric-phase optical element enabling on-demand
spin-controlled angular momentum multiplexing. A diffractive optics multiplexer
fabricated with 3D high-resolution electron beam lithography performs a
conformal mapping for the conversion from linear to azimuthal phase gradients.
The latter is functionalized by a dynamic spin-orbit add-on that consists of a
self-engineered electrically-activated liquid crystal optical vortex generator
having large clear-aperture and high-resolution. By combining several
functionalities based on the optical angular momentum of light in a compact
manner, the proposed hybrid device could find applications in next-generation
high-dimensional mode switchers and routers based on orbital angular momentum.
