The use of polariton materials and metamaterials to construct superlenses can surpass the limits of traditional optical imaging resolution, achieve better observation of sub wavelength level microstructures and biomolecules, and have a broad and revolutionary impact on fields such as physical chips, chemical materials, and life sciences. In 2000, Sir John Pendry from Imperial College London first proposed the concept of superlenses and predicted their ability to break through the resolution limits of traditional optical imaging. Immediately after that, Professor Xiang Zhang, a foreign academician of the Chinese Academy of Sciences, took the lead in proposing the experimental scheme of the new silver polymer superlens, which greatly promoted the development and application of the superlens technology. Since then, scientists from various countries have increased their research investment in superlenses, becoming a hot topic in the field of optics and widely used in biomedical, fiber optic communication, optical imaging and other scenarios. However, the optical loss of superlenses has always been a key scientific issue in this field, limiting further improvement in imaging resolution.

To address this challenge, the team of Professor Shuang Zhang and Academician Xiang Zhang from the University of Hong Kong, along with the team of Researcher Qing Dai from the National Center for Nanoscience and Technology and Sir John Pendry from Imperial College of Technology, have collaborated to propose a practical solution that utilizes multi frequency combination complex frequency wave excitation to obtain virtual gain, thereby offsetting the intrinsic loss of the optical system and achieving higher quality superlens imaging resolution. In order to verify the effectiveness of this theory, the collaborating team conducted experimental designs to synthesize complex frequency wave superlenses in both the microwave and optical frequency bands.

 In recent years, the Qing Dai research group has been conducting long-term research on improving the interaction ability between light and matter (Nat. Nanotechnology., 2023, 18, 529), exploring highly compressed polariton materials (Nat. Material., 2021, 20, 43) and device design (Science, 2023, 379, 558) under atomic manufacturing technology. They have accumulated rich experience in the field of near-field optical imaging technology, thus laying a strong experimental foundation for the design of polariton superlenses in the optical frequency band.

Furthermore, after in-depth discussions between Qing Dai's research group and collaborators, a silicon carbide phonon polariton superlens based on synthetic complex frequency waves was created, achieving a resolution improvement of about one order of magnitude in superlens imaging, which will have a huge impact on the field of optical imaging. Therefore, the method of synthesizing complex frequency waves is a practical technique to overcome the intrinsic losses of photonics systems. It not only has excellent performance in the field of superlens imaging, but can also be extended to other fields of optics, such as polariton molecular sensing and waveguide devices. This method can also be customized for different systems and geometric shapes, providing a potential approach to improve multi band optical performance and design high-density integrated photonic chips,

      On August 18th, the related research results were published online in the Science journal under the title of Overcoming losses in superlenses with synthetic waves of complex frequency. Researcher Qing Dai from the National Center for Nanoscience Technology, Sir John Pendry from Imperial College London, and Academician Xiang Zhang and Professor Shuang Zhang from the University of Hong Kong are the co corresponding authors of this article. Postdoctoral researcher Fuxin Guan from the University of Hong Kong, Special Research Assistant Xiangdong Guo from the National Center for Nanoscience Technology, and doctoral student Kebo Zeng from the University of Hong Kong are co authors. The above research work has been supported by projects such as the National Key Research and Development Program for Nanotechnology Frontiers and the National Natural Science Foundation of China.

       Paper link: https://www.science.org/doi/10.1126/science.adi1267

Schematic diagram of the principle of using synthetic complex frequency waves to improve the imaging quality of superlenses