Professor Chen Yang of University of Science and Technology of China, Xiao Shumin, Professor of Harbin Institute of Technology Shenzhen Campus, and Professor Qiu Chengwei of the National University of Singapore cooperated to introduce micro-tilt disturbances in the metasurface of the medium, and for the first time realized and observed the bound state in the continuous domain with extreme intrinsic chirality, and obtained a circular dichromatographic signal of up to 0.93 and an optical quality factor of up to 2663 in the optical band, which significantly enhanced the chiral interaction between light and matter. This research has a wide range of application prospects in the field of chiral optics. The research results were recently published in Nature.
Chirality is widespread in nature (Source: Wikipedia)
An object is chiral when it cannot coincide with its mirror body by rotating, translating, etc. Chen Yang introduced, “Chirality is widely found in nature, such as our hands, the left hand and the right hand mirror each other and cannot coincide. More importantly, the basic macromolecules that make up living organisms, such as amino acids, ribonucleic acid, monosaccharides, etc., have chiral structures. ”
In fact, Science magazine listed “Why does life need chirality” in its latest “125 Cutting-Edge Scientific Questions in the World”.
“Therefore, studying the chirality of substances not only helps to explore the mystery of the origin of life, but also has important application value in disease diagnosis, drug development, food and cosmetics and other fields in terms of specific applications.” Chen Yang gave an example, “For example, the composition of some characteristic chiral molecules in the body fluids of patients such as Parkinson’s syndrome and Alzheimer’s disease is very different from that of healthy people. 96% of drugs on the market are composed of chiral molecules, such as levofloxacin, dextroibuprofen, etc. ”
Chiral optical method is a common method to study the chirality of substances, and its core research is to enhance the chiral interaction between light and matter. However, the intrinsic chirality of matter in nature is usually extremely weak, and the chiral optical response it produces is difficult to detect.
The bound state in the chiral continuum is a singular optical state with extreme endochirality and high-quality factors. Although the internationally renowned research group has studied this optical state theoretically, these works are still in the theoretical stage because the structural design is difficult to achieve experimentally. In this study, the collaborative team innovatively proposed to use structural tilt to break the symmetry of the outer mirror of the metasurface of titanium dioxide medium, and combined with the trapezoidal nanopore design in the plane to achieve a three-dimensional true chiral structure, and at the same time clearly revealed the physical mechanism of this design based on the microscopic model and the general theory of chiral optics.
In order to prepare this inclined nanopore metasurface, the researchers developed a set of oblique reactive ion etching process, which uses the ion beam emitted by the radio frequency source and collimated to etch the sample placed on the inclined substrate, which realizes the precise control of the inclination angle of the nanopores and shows good consistency throughout the metasurface region.
Experiments have measured that the circular dichromatography-chromatography of the metasurface is as high as 0.93, close to the limit value of 1, and the optical quality factor is as high as 2663, which is more than an order of magnitude higher than the existing chiral metamaterials.
It can be said that the bound metasurface system in the chiral continuum domain developed this time can significantly enhance the chiral interaction between light and matter, and has broad application prospects in the fields of chiral light source and light detector, trace detection of chiral substances, and asymmetric photocatalysis.
The reviewer of Nature said, “This achievement represents an important breakthrough in the field of chiral optics” and “It is very impressive that this work can achieve such a high quality factor and strong chiral optical response.” (Source: Wang Min, China Science News)
Related paper information:https://doi.org/10.1038/s41586-022-05467-6