基于超材料的太赫兹幅度调制器设计

Design of Metamaterial-Based Terahertz Amplitude Modulator

摘要:

提出了一款基于超材料的太赫兹幅度调制器,其结构由开口“弓”形超材料结构、高电子迁移率晶体管、斜十字馈线和碳化硅衬底四部分构成。“弓”形超材料结构开口处的连通和断开两种状态将对通过该结构的太赫兹波产生不同的响应。在开口处添加高电子迁移率晶体管可模拟开口连通和断开的效果。当对晶体管上的栅极不施加偏压时,超材料结构开口相当于导通,对太赫兹波透射系数高；当对晶体管上的栅极施加偏压时,超材料结构开口相当于断开,对太赫兹波透射系数低。仿真结果表明,在0.22THz处,对晶体管栅极不施加偏压时,调制器的透射系数为0.579；对晶体管栅极施加偏压时,调制器的透射系数为0.040。通过公式计算得到其调制深度为93%,而且对x和y极化入射波具有不敏感的特性。同时,通过分析0.22THz处的电场分布和表面电流分布研究了该太赫兹调制器的工作原理。所设计的太赫兹调制器具有调制深度高、结构简单和易于加工等特点,在太赫兹通信领域具有广阔的应用前景。

Abstract:

A metamaterial-based terahertz amplitude modulator is proposed with the structure consisting of an open "bow" shaped metamaterial structure, a high electron mobility transistor, an oblique cross feeder and a silicon carbide substrate. Whether the openings of the "bow" shaped metamaterial structure are connected or disconnected will produce different responses to the terahertz waves passing through the structure. The effect of connecting and disconnecting the openings can be simulated by adding high electron mobility transistors to the openings of the "bow" shaped metamaterial structure. When no bias voltage is applied to the gate of the transistor, the opening of the metamaterial structure is equivalent to conduction, and the transmission coefficient to terahertz waves is high; when bias voltage is applied to the gate on the transistor, the opening of the metamaterial structure is equivalent to disconnection, and the transmission coefficient of terahertz waves is low. The simulation results show that the transmission coefficient of the modulator is 0.579 at 0.22THz when no bias is applied to the transistor gate, while it is 0.040 at 0.22THz when bias is applied to the transistor gate. The modulation depth of 93% is obtained by the equation, and the modulator is insensitive to x- and y-polarized incident waves. Meanwhile, the operating principle of this terahertz modulator is studied by analyzing the electric field distribution and surface current distribution at 0.22THz. The terahertz modulator designed in this paper is characterized by high modulation depth, simple structure and easy processing, which has a broad application prospect in the field of terahertz communication.