Multi-parameter tunable phase transition based terahertz graphene plasmons and its application

Abstract

The active modulation of the amplitude and phase of terahertz wave has been widely adopted in terahertz functional devices. The current metal-insulator-metal metasurface structure combined with two-dimensional materials such as graphene can realize dynamic control of terahertz amplitude/phase, but it has some disadvantages such as less freedom of control (voltage or light intensity), complex processing technology and high price of metasurface structure. In this article, we propose a prism-coupled matel-insulator-graphene (MIG) phase regulation structure. This structure can not only control the phase by adjusting the Fermi level in the usual way, but also change the intrinsic loss and radiation loss of the structure by adjusting the thickness of the air gap and the number of layers of pre-spread graphene, so that the phase of the structure can be controlled, which is determined by the difference between intrinsic loss and radiation loss of the fabric, which is closely related to this structure staying in the under-coupling/over-coupling state. The adjustment of the structural phase can also lead the magnitude of the terahertz Goos–Hänchen(GH) displacement and its positive sign and negative sign to be selected. Furthermore, it is shown that the under-coupling state and the over-coupling state of the structure have an important effect on the coincidence of the Goos–Hanchen (GH) displacement. The results show that by dynamically adjusting the thickness of the air gap and the Fermi level of graphene, and changing the eigenloss and radiation loss of the system, the phase regulation can be achieved. Finally, the transition from overdamped to underdamped state is realized. In this physical process, the GH displacement of the system will also change obviously. This paper puts forward the structure of the process with simple processing technology (no need to microstructure), tunable high degrees of freedom (available graphene Fermi level and air gap dynamic regulation, also could be regulated and controlled by controlling the graphene layers) in comparison with the phase modulator of metal-insulator-metal super surface structure. The results of this paper open up a new way of developing the multi-parameter tunable terahertz sensor components.