  Optical prisms are made of glass and map temporal frequencies into spatial
frequencies by decomposing incident white light into its constituent colors and
refract them into different directions. Conventional prisms suffer from their
volumetric bulky and heavy structure and their material parameters are dictated
by the Lorentz reciprocity theorem. Considering various applications of prisms
in wave engineering and their growing applications in the invisible spectrum
and antenna applications, there is a demand for compact apparatuses that are
capable of providing prism functionality in a reconfigurable manner, with a
nonreciprocal/reciprocal response. Here, we propose a nonreciprocal
metasurface-based prism constituted of an array of phase- and
amplitude-gradient frequency-dependent spatially variant radiating super-cells.
In conventional optical prisms, nonreciprocal devices and metamaterials, the
spatial decomposition and nonreciprocity functions are fixed and noneditable.
Here, we present a programmable metasurface integrated with amplifiers to
realize controllable nonreciprocal spatial decomposition, where each frequency
component of the incident polychromatic wave can be transmitted under an
arbitrary and programmable angle of transmission with a desired transmission
gain. Such a polychromatic metasurface prism is constituted of
frequency-dependent spatially variant transistor-based phase shifters and
amplifiers for the spatial decomposition of the wave components. Interesting
features include three-dimensional prism functionality with programmable angles
of refraction, power amplification, and directive and diverse radiation beams.
Furthermore, the metasurface prism can be digitally controlled via a
field-programmable gate array (FPGA), making the metasurface a suitable
solution for radars, holography applications, and wireless telecommunication
systems.
