基于偏振耦合特性的新型全光纤调制器研究

This project intends to combine polarization maintaining fiber with graphene material, which has an ultra-wide bandwidth of the light waves and fast response, to study an integrated all-fiber polarization modulator. By covering the surface of the fiber core with graphene, a light coupling between the fiber and the graphene through the evanescent field is formed. Apply a modulated signal to the graphene and the electronic Fermi level of the graphene changes, thus leading to a change of the light intensity absorption of the graphene from the fiber core, and consequently realizing the modulation on the optical signal of the fiber core. Compared with traditional light modulator, the integrated all-fiber modulator has the advantages of high-bandwidth and high-frequency response. Hence, this modulator can achieve ultra-wide bandwidth modulation from the visible to near-infrared bands. This fiber integrated device can be directly coupled with primary transmission medium, including optical fiber. This work is important to the rapid development of optical fiber communications, fiber optic sensing and fiber-optic gyroscope, and a significant explore for the field of new micro-scale fiber integrated devices.

本项目拟将保偏光纤与对光波具有宽波长、超快响应的石墨烯相结合，研究一种集成式全光纤偏振光调制器。通过在保偏纤芯表面键合石墨烯，使纤芯与石墨烯之间通过波导表面倏逝场形成偏振光耦合，利用石墨烯优异的电子迁移特性，对石墨烯施加高速调制信号，改变石墨烯电子的费米能级，实现纤芯与石墨烯的能量交换，完成对纤芯的偏振光的高频强度调制。与传统光调制器相比，这种集成式全光纤调制器将具备超高频响应的优势，并能覆盖可见至近红外不同波段的工作波长。这种全光纤调制器能够与光纤等主流信息传输介质以及光纤类型的有源及无源器件直接耦合，对飞速发展的光纤通讯、光纤传感及光纤陀螺等领域具有重要的实际意义，也是对新型特种光纤集成器件领域发展的重要探索。

光调制器在光电领域中具有重要的研究意义，本项目对光纤进行微加工，构造D型平面光纤倏逝场结构，并利用化学气相沉积法合成石墨烯材料，将其转移结合在纤芯表面，使石墨烯和纤芯形成光耦合。通过在石墨烯(Graphene)表面制备电极，对石墨烯施加电场，控制石墨烯的费米能级及对偏振光的吸收，实现了微加工光纤与Graphene集成的光强调制器或光开关结构。项目组具体对微加工光纤、石墨烯材料制备、转移修饰、器件光强调制方法等方面进行了研究，具体开展的工作包括：1）分析了石墨烯的光学特性，包括石墨烯材料的复折射率传输特性、电导率实部与化学势的关系、电导率虚部与化学式的关系等，并探讨了Graphene介电常数随化学势及偏置电压的变化情况；2）利用设计的D型光纤结构，在光纤外表面构建石墨烯及电极，设计光纤调制结构，建立仿真模型，利用有限元仿真软件进行理论计算，分析光纤的调制特性；3）通过侧抛微加工技术对光纤进行微加工，制备所需的调制微结构，在光纤外表面修饰石墨烯，并制备电极结构，通过外部电压控制，利用Graphene对光纤内传输光在倏逝场范围的光吸收变化，实现了光纤内光强的调制效果。