  Metasurfaces are believed as one of the best candidates in nano-optical
devices, attributed to the key feasible modulation features of phase,
polarization, and local field enhancement by structural designing. However,
current methods of propagation- and geometric-phase modulation are interrelated
between two eigen spin-states. This means that when the left-handed component
phase of a beam is modulated by metasurfaces, its right-handed component phase
will change accordingly, which limits the versatility of spin-decoupled
applications. In this paper, we experimentally and numerically demonstrate a
new phase modulation pathway based on chiral V-shaped holes, which enable fully
decoupled one-handed phase modulation of the two eigen spin-states. Two
enantiomers are proposed to realize decoupled functions for the two
eign-states, e.g., the enantiomer can manipulate the left-handed component
phase of a laser beam without changes of the right-handed component. This
proposed method has significant meaning in metasurfaces, which can expand the
methods of phase engineering.
