Harvard Engineers Develop Chip-Scale MEMS Device for Real-Time Dynamic Control of Optical Chirality and Light Handedness

New MEMS-integrated photonic crystal from Harvard SEAS allows for real-time control of light's handedness, revolutionizing chiral sensing and quantum tools.

By: AXL Media

Published: Mar 13, 2026, 7:22 AM EDT

Source: Information for this report was sourced from Harvard John A. Paulson School of Engineering and Applied Sciences

Engineering Asymmetry at the Nanoscale

Optical chirality, the property of light that defines its "handedness" as it propagates in a helical pattern, is a fundamental characteristic used to probe the molecular structure of everything from pharmaceuticals to biological tissues. While traditional optics require static, bulky components to manipulate this property, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences have developed a chip-scale solution. By stacking two photonic crystals and introducing a precise twist, the team has created a geometrically chiral structure that interacts differently with left- and right-circularly polarized light. This innovation, led by Professor Eric Mazur, translates the principles of "twistronics" into the realm of photonics, providing a platform that is both powerful and compatible with modern manufacturing processes.

The Role of MEMS in Dynamic Light Modulation

The breakthrough of the Harvard device lies in its integration with micro-electromechanical systems (MEMS), which allow for the real-time physical adjustment of the crystal layers. Unlike previous static models, this device can dynamically vary both the twist angle and the vertical spacing between the two silicon nitride membranes. This mechanical tunability enables the device to "dial" its optical response up or down, changing how it filters or reads chiral light without requiring a change in hardware. According to graduate student Fan Du, this reconfigurability is essential for creating versatile tools that can adapt to different wavelengths or sensing requirements on a single chip.

Overcoming the Challenges of Chiral Detection

Detecting the difference between mirror-image states of light is a delicate process, as the physical signatures are often minute. In traditional chemistry and pharmacology, distinguishing between these "handed" molecules is a matter of safety and efficacy, as seen in historical cases where one version of a drug provided therapy while its mirror image caused harm. The Harvard team’s bilayer design addresses this by fostering strong coupling between the optical modes of the two layers. This coupling results in dramatically different transmission rates for left- versus right-circular polarized light when the beams hit the surface perpendicularly, a phenomenon known as normal incidence.