  We propose a novel design of a true 3D chiral metasurface behaving as a
spatial polarization converter with asymmetric transmission. The metasurface is
made of a lattice of metallic sesquialteral (one and a half pitch) helical
particles. Each particle contains six rectangular bars arranged in a series one
above the another creating a helix The proposed metasurface exhibits a
dual-band asymmetric transmission accompanied by the effect of a complete
polarization conversion in the response on the particular distributions of
currents induced in the particle's bars by an incident wave. Regarding
circularly polarized waves the metasurface demonstrates a strong circular
dichroism. A prototype of the metasurface is manufactured for the microwave
experiment by using 3D-printing technique utilizing Cobalt-Chromium alloy,
which exhibits good performances against thermal fatigue and corrosion at high
temperatures. Our work paves the way to find an industrial solution on
fabricating communication components with efficient polarization conversion for
extreme environments.
