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Principle innovation! Scientists further improve the resolution of metalenses


Metalenses can go beyond the limits of traditional optical imaging resolution, enabling better observation of microstructures and biomolecules at subwavelength levels. However, intrinsic loss of metalenses has been a long-standing key scientific problem in this field, limiting further improvements in imaging resolution.

Recently, researchers from the University of Hong Kong, the National Centre for Nanoscience and Imperial College London and other institutions have worked closely together to propose a theoretical mechanism for multi-frequency combined complex frequency wave-excited ultralens imaging, which offsets the intrinsic loss through virtual gain and successfully improves the imaging resolution of the superlens by about one order of magnitude. The findings were published online in the journal Science on August 18.

The concept of “metalensing” was first proposed by Imperial College London professor John Pendry in 2000. According to theoretical predictions, ultralenses will have the ability to push the limits of resolution of traditional optical imaging. Subsequently, in order to realize the concept of ultralens, the team of Zhang Xiang, a foreign academician of the Chinese Academy of Sciences and professor of the University of Hong Kong, took the lead in proposing an experimental scheme for a new silver-polymer ultralens, which greatly promoted the development and application of ultralens technology. Since then, scientists from all over the world have increased their research investment, and ultralenses have quickly become a hot topic in the field of optics, and have been widely used in biomedicine, optical fiber communication, optical imaging and other scenarios.

Schematic diagram of the synthetic complex frequency wave method to improve the imaging quality of ultralenses (Photo courtesy of the research team)

At present, ultralenses based on polarion materials and metamaterials have been widely verified to achieve subdiffraction imaging, but their intrinsic loss seriously limits their resolution and thus their application development.

In order to solve this major challenge, an international research team composed of professors Zhang Shuang and Zhang Xiang of the University of Hong Kong, Dai Qing and John Pendry, researchers of the National Center for Nanoscience and Technology, carried out joint research.

In the latest paper, Zhang Shuang introduced: “A practical solution for optical loss is proposed, that is, to obtain virtual gain by using multi-frequency combination complex frequency wave excitation, thereby canceling the intrinsic loss of optical systems. ”

As a verification, they applied this scheme to the ultralens imaging mechanism, and theoretically achieved a significant improvement in imaging resolution. Finally, the microlens experiment of microwave band hyperbolic metamaterials is further demonstrated, and a good imaging effect consistent with the theoretical expectation is obtained.

Based on the long-term accumulation of high-momentum polaritons under atomic manufacturing technology, Dai Qing’s team created a silicon carbide phonon polarion ultralens based on synthetic complex frequency waves. “We have finally achieved an order of magnitude improvement in the imaging resolution of the superlens, which we believe will have a huge impact on the field of optical imaging.” Dai Qing said.

Researchers introduced that synthetic complex frequency wave technology is a practical method to overcome the intrinsic loss of photonic systems, which not only has excellent performance in the field of ultralens imaging, but can also be extended to other fields of optics, including polarion molecular sensing and waveguide devices. This method can also be customized for different systems and geometries, providing a potential way to improve multi-band optical performance and design high-density integrated photonic chips.

“This is a beautiful and universal method that can be extended to other fluctuation systems to compensate for losses, such as sound, elastic and quantum waves.” Zhang Xiang said.

Fuxin Guan, a postdoctoral fellow at the University of Hong Kong, Xiangdong Guo, a special research assistant at the National Center for Nanoscience and Technology, and Kebo Zeng of the University of Hong Kong. Shuang Zhang, Xiang Zhang, Qing Dai and John Pendry are co-corresponding authors. (Source: China Science News Gan Xiao)

Related paper information:https://doi.org/10.1126/science.adi1267



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