tect toxic or explosive chemicals, or use it
in high-speed data processing systems and
Terahertz-based polarimetric devices
also could benefit medical researchers and
developers of pharmaceutical drugs because most biological molecules, including DNA, RNA and proteins, are chiral.
“In THz, most of the biological mole-
cules show circular dichroism,” Zhang said.
“However, there is a lack of spectroscopy
tools to accurately measure the circular
dichroism of biomolecules at THz in com-
parison with the visible range. The sensitive
detection of circular dichroism requires dy-
namic modulation of the electromagnetic
waves between the two circular polariza-
tions. The chirality-switching metamaterial
we demonstrated may bridge this gap.”
Their design principle for optically
switchable chiral terahertz metamolecules
is not limited to just handedness switching;
it also could be applied to dynamic revers-
ing of other electromagnetic properties.
“Dynamically reversing other electro-
magnetic properties would enable us com-
In this schematic, the chirality-switching metamolecule consists of four chiral resonators with fourfold
rotational symmetry. An external beam of light instantly reverses the metamolecule’s chirality from
right-handed to left-handed.
plete control of electromagnetic waves, not
only in polarization, but also in phase, intensity and propagation directions,” Zhang
said. “For example, we can use a similar
design principle to make a meta-surface
with dynamically switchable high and low
impedance. For a THz wave reflected by
the meta-surface, the phase can be dynamically switched between 0 and 180 degrees.
“The metamaterials we demonstrated so
far still have some drawbacks: Chirality is
not strong enough to completely convert
the THz waves into purely circular polar-
izations. We will work on the perfection of
the metamaterial design to achieve a
stronger chirality switching effect.”
The work was published in Nature Com-
munications (doi: 10.1038/ncomms 1908).
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