Figure 1: A droplet of the ferroelectric liquid crystals viewed under three different wavelengths of light. © 2026 Wiley-VCH GmbH
The direction in which the electromagnetic field of circularly polarized light rotates can be easily reversed by applying a voltage, RIKEN researchers have demonstrated1. This could enable a new generation of optical devices based on circularly polarized light.
Polarized sunglasses produce light that is polarized along a single direction. But some special devices can generate light with a polarization that rotates as the light propagates. Such circularly polarized light is useful for many applications, including spectroscopy, satellite communications, stereoscopy and microscopy.
For some applications, it would be useful to switch between clockwise and anticlockwise circularly polarized light. However, this handedness is locked into the molecular structure. Known as the material's chirality, it is used to produce the circularly polarized light. And reversing that requires a lot of energy.
Helical liquid crystals naturally produce circularly polarized light, making them attractive for chirality control. The catch is that neighboring molecules grip each other so tightly in these helices that reversing the handedness electrically has proven virtually impossible.
Hiroya Nishikawa of the RIKEN Center for Emergent Matter Science and colleague Fumito Araoka work with ferroelectric liquid crystals-materials that respond to an applied voltage. Previously, they had found a way to impose twists on these materials by rubbing polymer microgrooves onto opposing surfaces of glass cells2.
Nishikawa realized that this external twist could combine with materials that naturally have internal helices. "We wondered how the extrinsic and intrinsic chiralities would interact, and what kind of hierarchical twist field might emerge," he explains.
To test this, Nishikawa's team used a newly discovered phase in which molecules spontaneously form helices with pitches of a few hundred nanometers. They placed this material in cells with opposing rubbed surfaces. The result: a hierarchical structure with nanoscale molecular coils nested inside microscale surface twists.
Applying electric fields perpendicular to rubbing triggered a cascade. At ultralow electric fields, the material flipped from absorbing left-handed light to absorbing right-handed light-evidence that the surface twist had reversed, pulling the molecular helices into new orientations.
"Such a phenomenon is unattainable with a single chiral source," notes Nishikawa.
Switching the field to parallel alignment produced an entirely different effect. The material developed periodic striped patterns that acted as diffraction gratings, splitting light into component colors like a prism.
This dual functionality-chirality switching in one geometry, diffraction control in another-emerged from the hierarchical structure in ways that theory hadn't predicted. Both modes switch at ultralow voltages, respond rapidly and retain memory without power.
Applications could range from energy-efficient wearable displays to on-chip circularly polarized light sources for quantum devices.
"Most importantly, it demonstrates that chirality-based photonic functions can be electrically switchable in bulk systems," says Nishikawa. "This dramatically expands the design space for optical devices."
Hiroya Nishikawa's team has achieved electric control over light's chirality using liquid crystals that switch at ultralow voltages. © 2026 RIKEN
