Progress has been made in the research of phase modulation of terahertz programmable metasurfaces based on free carrier plasmonic dispersion effect

Recently, the team of Situ Guohai and Guo Jinying from the Aerospace Laser Technology and Systems Department of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, and the School of Microelectronics at Shanghai University collaborated to propose a terahertz phase controlled programmable metasurface design scheme based on free carrier plasma dispersion effect. The related research results were published in Applied Physics Letters under the title "Terahertz programmable metasurface for phase modulation based on free carrier plasma dispersion effect".

Terahertz modulators have broad application prospects in fields such as terahertz intelligent communication and computational imaging. However, existing terahertz phase modulators are not satisfactory in terms of speed, efficiency, and flux. Therefore, there is an urgent need to develop high-speed, efficient, and high-throughput terahertz spatial light modulators.

The research team proposed a terahertz programmable metasurface design scheme based on the free carrier plasmonic dispersion effect. By integrating the pn junction into the "H" - shaped metal metasurface unit structure and utilizing the change in external voltage to alter the carrier concentration distribution of the pn junction, continuous phase control at a frequency of 0.4 THz and 270 ° with an average efficiency of 30% were achieved in simulation. The metasurface unit adopts a "MIM" structure, and each unit is independently adjustable, while utilizing the high-speed switching characteristics of the pn junction, which is expected to achieve GHz level control speed. The team also demonstrated the far-field radiation results of the metasurface unit array, with a peak sidelobe ratio of 13dB, demonstrating excellent beam steering performance. The high-speed, efficient, and high-throughput advantages demonstrated by this design scheme in terahertz phase modulation are expected to play an important role in terahertz communication and imaging fields.

Figure 1. Schematic diagram of programmable metasurface unit structure and beam steering function

Figure 2. Continuous phase modulation of metasurface units under voltage

This research achievement has received support from the National Natural Science Foundation of China, the Shanghai Academic Research Leader Project, and the Shanghai Municipal Science and Technology Major Project.

Source: Shanghai Institute of Optics and Fine Mechanics