U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has developed artificial molecules whose chirality can be rapidly switched from a right-handed to a left-handed orientation using terahertz (trillion-cycles-per-second) electromagnetic radiation (paper).

Chirality switching meta-molecule consists of four chiral resonators with fourfold rotational symmetry. An external beam of light instantly reverses the meta-molecule’s chirality from right-handed to left-handed. (courtesy of Zhang, et. al)

 Actually, natural materials can be induced to change their chirality but the process, which involves structural changes to the material, is weak and slow.

Using terahertz (THz) meta-materials (engineered from nanometer-sized gold strips with air as the dielectric) they created a delicate artificial chiral molecule which they then incorporated with a photoactive silicon medium.

Through photoexcitation of their meta-molecules with an external beam of light, the researchers observed chirality flipping (in former demonstrations chirality was merely switched on or off in meta-materials using photoelectric stimulation). Specifically, optically switchable chiral THz meta-molecules consisted of  a pair of 3D meta-atoms of opposite chirality made from precisely structured gold strips.

These achievements may have potentially interesting applications of THz communications and technologies across a wide range of areas, e.g. energy use for data-processing, security and ultra high-speed communications.