Light Untwisted: How Terahertz Waves Are Rewriting the Rules of Chemistry

Imagine a form of light that can temporarily make a material left-handed or right-handed, control the behavior of semiconductors at an atomic level, or even influence the function of nerve cells without causing damage.

This isn't science fiction—it's the emerging reality of terahertz molecular science, a field that explores the mysterious region of the electromagnetic spectrum between microwaves and infrared light.

The extraordinary power of terahertz science lies in its unique position on the electromagnetic spectrum. Ranging from 0.1 to 10 THz (with wavelengths between 0.03-3 mm), terahertz radiation interacts with materials at energy scales that match their natural vibrational rhythms ³ .

Professor Keisuke Tominaga of Kobe University, a pioneer in this field, explains that in molecular crystals, "the normal modes are generally a mixture of intermolecular and intramolecular vibrational modes" ¹ . This means terahertz light can simultaneously probe both the internal vibrations of molecules and how they move relative to their neighbors.

What makes this band particularly promising for biomedical applications is that its photons carry comparatively low energy—not enough to ionize tissue or damage DNA, unlike X-rays or ultraviolet radiation ³ . This combination of penetrating ability and safety opens doors to non-destructive testing and live detection in biological samples.

One of the most stunning demonstrations of terahertz control recently came from a collaboration between the Max Planck Institute for the Structure and Dynamics of Matter and the University of Oxford. In early 2025, researchers announced they had used terahertz light to induce chirality in a non-chiral crystal—a feat previously thought impossible without melting and recrystallizing the material ⁵ .

What is Chirality?

Chirality, from the Greek word for "hand," describes objects that exist in left- and right-handed forms that are mirror images but cannot be superimposed. Your hands are the perfect example—no matter how you rotate them, they can't be perfectly aligned.

In chemistry, chiral molecules have identical compositions but opposite handedness, which can lead to dramatically different biological effects.

The team worked with boron phosphate (BPO₄), an "antiferro-chiral" crystal where equal amounts of left- and right-handed substructures cancel each other out ⁵ .

How They Twisted the Crystal

The experimental breakthrough relied on a sophisticated approach called nonlinear phononics ⁵ . Here's how it worked:

Why This Experiment Matters

This work demonstrates that material properties once considered permanent and static can be dynamically controlled with light. Professor Andrea Cavalleri, who led the research group, noted that "this discovery opens up new possibilities for the dynamical control of matter at the atomic level" and could lead to applications in "ultrafast memory devices or even more sophisticated optoelectronic platforms" ⁵ .

The ability to induce chirality is just one example of how terahertz science is revolutionizing multiple fields. Researchers are now applying these principles in increasingly sophisticated ways:

Advancing terahertz molecular science requires specialized equipment and materials. Here are some key components of the modern terahertz researcher's toolkit:

As terahertz technology continues to mature, its impact is spreading across scientific disciplines. The growing importance of this field is evident in dedicated conferences like the Terahertz Young Scientists Meeting ^{6 9} , which brings together early-career researchers to share breakthroughs in both fundamental and applied terahertz research.