基于三维微纳结构耦合增强的石墨烯太赫兹低损调制芯片研究

Restricted by the material and structures,the conventional terahertz modulator is hard to own high modulation depth and insertion loss at the same time at room tempetature. In this project, it is proposed that the coupling effect of the three dimentional micro-/nano-structure is used to largely enhance the interaction between the graphene and terahertz wave, which is hoped to enlarge the modulation depth of the modulation chip. Simultaneously, the low loss polymer film acting as the support material is combined to reduce the insertion loss of the modulation chip. With this idea, by researching the coupling resonance mode in the three dimentional micro-/nano-structure, make clear the physical mechanism of the interaction enhancement between the graphene and terahertz wave. And then build the theorical model of the terahertz transmission modulation. With the model, build the theory design method of realizing chip structures with high modulation depth and low insertion loss. After that, research the fabrication technology and process of the terahertz modulation structures combined with the low loss polymer support, three dimentional micro-/nano-structures and graphene films. Based on these methods, carry out the terahertz modulation chip fabrication and test experiment. With the data process, obtain the experimental demonstrations of the theories and fabrications. For the properties of high modulation depth and low insertion loss, and also owning the advantages of graphene with high modulation speed and esay to integrate, the proposed terahertz modulation chip will be a key device for the high speed terahertz wireless communication and will promote its development. Generally , the terahertz modulation chip will have a mass application at the densely populated areas with multi-terminal and high-capacity wireless communications, and the space high speed communications.

受材料和结构限制，传统太赫兹调制器难以在室温下兼顾调制深度和插损。本项目提出利用三维微纳结构空间耦合效应大幅增强石墨烯与太赫兹波的相互作用，提升调制芯片调制深度，同时结合低损聚合物薄膜支撑材料，降低调制芯片插损。通过研究三维微纳结构耦合共振模式，明晰其增强石墨烯二维薄膜与太赫兹波相互作用的物理机制，建立其透射调制理论模型及高调制深度、低插损芯片结构设计方法；研究以低损聚合物为支撑介质制备三维微纳结构和石墨烯复合的太赫兹调制结构的加工工艺和芯片制备方法，并在此基础上开展太赫兹调制实验，获得实验验证。该调制芯片因具有高调制深度、低插损性能，同时兼具石墨烯高速、高集成特点，将为太赫兹无线通信提供核心器件支撑，促进太赫兹高速无线通信技术的发展，在人口密集区多终端、大容量通信以及太空高速通信等领域具有重大应用前景。

受材料和结构限制，传统太赫兹调制器难以在室温下兼顾调制深度和插损。本项目提出利用三维微纳结构空间耦合效应大幅增强石墨烯与太赫兹波的相互作用，提升调制芯片调制深度，同时结合低损聚合物薄膜支撑材料，降低调制芯片插损。项目开展的主要研究内容和取得的成果包括：（1）建立了以传输线理论和有限元数值计算方法相结合的微纳结构增强石墨烯太赫兹调制的物理分析模型，获得了在低损传输下实现高调制深度的理论分析结果。首先采用有限元对增强微纳结构模式、宏观参数进行计算，然后针对增强微纳结构、石墨烯及绝缘层构成的增强调制器件，采用传输理论模型，通过对ABCD矩阵中参数的计算，获得了整个器件透过率光谱与增强微纳结构参数、石墨烯费米能级参数的理论关系。在此基础上，进一步地得到了石墨烯在不同费米能级参数下的透过率，由此建立了其对太赫兹幅度调制深度、调制效率的理论分析模型。（2）建立了基于硬质基底支撑法的多种增强微纳结构及石墨烯太赫兹幅度调制器件的实验制备。为了克服太赫兹波段聚合物薄膜的柔软性，在其表面制备大面积均匀性好的微结构的难点，本项目提出了一种新的工艺方法，以硬质硅片作为承载体，在其表面通过化学合成的方法，合成性质可控的聚合物薄膜，然后结合光刻工艺制备大面积微结构，将薄膜与硅片剥离，获得了有效面积超过40mm的大面积均匀的薄膜衬底太赫兹器件。基于该工艺方法成功制得基于不同薄膜衬底的多种增强微纳结构。在此基础上，通过与石墨烯湿法转移、调制电极制备等工艺结合，研制了4种不同增强结构的石墨烯太赫兹幅度调制器件。（3）开展了以所制备的石墨烯太赫兹调制器的实验测试验证，获得了预期的实验结果。采用太赫兹时域光谱系统(THz-TDS)，通过激发增强微纳结构的太赫兹共振，在0.5-0.6THz附近，获得了太赫兹幅度调制深度的大幅增强，在此基础上引入激光泵浦，进一步提升了太赫兹幅度调制效率，使其实验上获得的最大调制深度达到90.2%，插损为0.862dB，达到项目预期的技术指标。