Chiral Bilayer All-Dielectric Metasurfaces

Three-dimensional
chiral plasmonic metasurfaces were demonstrated
to offer enormous potential for ultrathin circular polarizers and
applications in chiral sensing. However, the large absorption losses
in the metallic systems generally limit their applicability for high-efficiency
devices. In this work, we experimentally and numerically demonstrate
three-dimensional chiral dielectric metasurfaces exhibiting multipolar
resonances and examine their chiro-optical properties. In particular,
we demonstrate that record high circular dichroism of 0.7 and optical
activity of 2.67 × 105 degree/mm can be achieved based
on the excitation of electric and magnetic dipolar resonances inside
the chiral structures. These large values are facilitated by a small
amount of dissipative loss present in the dielectric nanoresonator
material and the formation of a chiral supermode in a 4-fold symmetric
metasurface unit cell. Our results highlight the mechanisms for maximizing
the chiral response of photonic nanostructures and offer important
opportunities for high-efficiency, ultrathin polarizing elements,
which can be used in miniaturized devices, for example, integrated
circuits.