Innovative Materials Science Pioneered by Chiral Photonics
Understanding the universal property of chirality could lead to new materials and technologies for photonics and other applications
Of the many mysteries still to be unraveled in the natural sciences, one of the most compelling is the origin and power of chirality — the property of a molecule or object that has two mirror-image forms — like our left and right hands.
Chirality is universal in biology, chemistry and physics. It critically affects the biochemical processes underpinning life, is a vital aspect of drug discovery, and crops up in particle physics. Light can have chiral properties that affect how it interacts with matter. How can the power of chirality be harnessed and controlled? And what new discoveries and technologies might this give rise to? These are some of the questions Takashige Omatsu and his team are asking.
Light beams can be chiral when they are imparted with so-called helical wavefronts, that is, polarity that rotates either left or right. “We can use ‘optical vortices’ to twist the physical properties of metals, semiconductors and organic materials on the nanoscale to create chiral nanostructures with unique features,” says Omatsu.
“Our goal is to establish chiral photonic materials as an original research field and to pioneer new technologies such as chiral plasmonics and metasurfaces for nanoscale chiral chemical reactors, chiral-selective imagers and chiral sensors,” he explains.
Omatsu and his team focus on the interaction between helical light and materials, and the physical properties and potential uses of such modified materials. The electromagnetic field of helical light rotates as the light moves through space. When this electromagnetic field interacts with conductive materials like metals, nanoscale corkscrew-like variations in physical properties can be inscribed on the material’s surface. The modified surface can then react differently to left- and right-handed chiral molecules or helical light, giving rise to a range of interesting possibilities for chemical sensing, synthesis and imaging.
“We can use helical light to create nanostructures such as twisted needles, twisted reliefs and twisted fibers,” says Omatsu. “We have also found that the same process can polymerize fullerene — a well-known functional organic molecule that is normally not conductive. This causes fullerene to form a novel conductive metallic phase, which could be used as the basis for fabricating electronic devices without metals and semiconductors.”
Omatsu believes that ‘nanovortices’ will one day be used for nanoscale precision control of light polarization, electron orbital motion and the aggregation of chiral molecules.
“Our research will lead to the development of advanced materials for next-generation photonics and electronics, and new applications in chemical synthesis, pharmacy, biology and medicine,” he says. “It might also allow us one day to answer the scientific mystery: ‘Why does handedness exist in nature?’”
Omatsu has collaborated with many Japanese and international researchers, and he is always looking for students and early career researchers to join collaborative projects.
“Our research center brings together physicists, chemists, biologists and even medical doctors to work together, and we frequently have brain-storming meetings to think up ideas for new collaborative research projects,” he says. “Several international researchers work here as faculty members. There is a wonderful diversity of backgrounds and expertise.”