Harvard Engineers Develop Chip to Dynamically Control Light’s ‘Handedness’ for Advanced Sensing and Quantum Technologies

Cambridge, MA – Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have announced a breakthrough in photonics: a chip-scale device capable of dynamically controlling the chirality of light – its “handedness” – with a simple twist. This innovation, published in Optica on March 11, 2026, promises advancements in chiral sensing, optical communication, and quantum photonics.

Controlling Chirality on a Chip

The device utilizes a reconfigurable twisted bilayer photonic crystal, adjusted in real-time using an integrated micro-electromechanical system (MEMS). This allows for precise tuning of how light interacts with the structure, distinguishing between left- and right-circular polarized light.

“Chirality is very important in many fields of science – from pharma to chemistry, biology, and of course, physics and photonics,” said Eric Mazur, the Balkanski Professor of Physics and Applied Physics, who led the research team. “By integrating twisted photonic crystals with MEMS, we have a platform that is not only powerful from a physics standpoint but also compatible with the way modern photonics are manufactured.”

How it Works: Twisted Photonic Crystals and MEMS Integration

Photonic crystals, nanoscale structures designed to control light behavior, are at the heart of the innovation. The Harvard team built upon recent advances in twistronics, inspired by the discovery of twisted bilayer graphene. By stacking two patterned silicon nitride membranes and rotating them relative to each other, they created new optical properties.

Chirality, in the context of light, refers to its helical pattern of travel. Light can be either right-circularly polarized (rotating clockwise) or left-circularly polarized (rotating counterclockwise). While subtle, these differences are crucial in applications like chemistry, where distinguishing between mirror-image molecules is vital – as demonstrated by the historical case of thalidomide.

The key to the device’s tunability lies in the bilayer design. When the two photonic crystals are twisted and brought close together, the resulting structure becomes geometrically chiral, effectively “reading” chiral light. The MEMS device allows continuous variation of the twist angle and interlayer spacing, enabling precise control over the device’s response to different chiral light modes.

Potential Applications

This technology opens doors to several exciting possibilities:

• Chiral Sensing: Devices could be tuned to probe different chiral molecules at specific wavelengths.
• Optical Communications: Dynamic light modulators could enable on-chip control of light for faster and more efficient data transmission.
• Quantum Photonics: The ability to manipulate the chirality of light could be leveraged for advanced quantum technologies.

The research provides a general design framework for twisted bilayer crystals exhibiting optical chirality, paving the way for future development and integration into various photonic systems. The project was led by graduate student Fan Du in Eric Mazur’s lab.