On October 11, Li Yue, Associate Professor of the Department of Electronic Engineering, Tsinghua University, published a research paper entitledStructural dispersion–based reduction of loss in epsilon-near-zero and surface plasmon polariton wavesinScience Advances. To address the problem of propagation loss of electromagnetic waves in plasma materials, a reduction method based on the waveguide structure was proposed to increase the transmission distance of electromagnetic waves in plasma materials and a feasible program was provided for related technologies of low-loss plasma.

Plasmonics has developed rapidly in the past ten years. It is a discipline that manipulates and regulates electromagnetic fields on a sub-wavelength scale in the optical frequency band. It presents a unique interaction between light and matter, and achieves sub-wavelength or deep subwavelength devices and circuits. But the propagation of electromagnetic waves in plasma is severely limited by the internal loss of plasma materials (such as gold, silver), thus limiting the practical application of plasma materials in optical systems and devices. The current research is mainly concentrated in the material field. Looking for a variety of plasma materials with low loss characteristics, such as indium tin oxide, silicon carbide, still can't meet the realization needs.

Photo 1Reduction methods of the propagation loss of electromagnetic waves in plasma materials: (A) Waveguide loading structure, (B) Loss control mechanism

In this paper, the reduction of the propagation loss of electromagnetic waves in plasma materials was studied from another perspective, that is, the propagation distance of electromagnetic waves is increased by adding electromagnetic structures. In this paper, the structural dispersion characteristics of the waveguide were used to control the material dispersion characteristics of the plasma itself, and the effective working frequency range of the plasma was moved from the high-loss range to the low-loss range, thus reducing the propagation loss of electromagnetic waves in plasma. In this paper, the propagation in two typical plasma materials was studied. One is the propagation of electromagnetic waves in epsilon-near-zero materials; the other is the propagation in surface plasmon polariton materials. From the two examples, it is observed that the propagation distance of electromagnetic waves in the plasma material is significantly improved and the propagation loss is effectively controlled by increasing the waveguide structure. In this paper, a structure-based plasma loss control technology was proposed and has potential application value in the future research of low-loss plasma devices and systems.

Photo 2Based on structural dispersion characteristics, the propagation distance of electromagnetic waves in the plasma was increased

The related work of this paper was completed in Tsinghua University, and the Department of Electronic Engineering, Tsinghua University is the first unit of the paper. Associate Professor Li Yue is the first author of the article, and Professor Nader Engheta from the Department of Electrical & Systems Engineering, University of Pennsylvania is the corresponding author of this article. Other authors include Dr. Inigo Liberal from the Public University of Navarre. The research was sponsored by the National Natural Science Foundation of China (61771280).

Paper link: https://advances.sciencemag.org/content/5/10/eaav3764