聚合物填充环形光子晶体波导的宽带可调慢光特性及全光缓存应用研究

To satisfy the high integration requirements of optical components in all-optical networks, extensive attention has been paid by scholars both at home and abroad to developing new all-optical buffers based on the slow light effect in two-dimensional photonic crystal waveguides. Since the structure of unit cell in current widely used two-dimensional photonic crystal waveguides is composed of simple air holes, this may restrict the improvement of buffering performance and dynamic modulation performance of optical buffers due to the conflict between group index and bandwidth of slow light. In the present project, we will carry out the study of buffering based on a new type of structure, i.e., two-dimensional photonic crystal slabs with annular unit cell. The working mechanisms and corresponding adjusting rules of such annular structure in improving both group index and bandwidth of slow light will be investigated. Particularly, considering different structures and refractive indexes of nonlinear fillers, we will study the sensitive modulation performance of dispersion curves by using effective index method based on the plane wave expansion and the finite difference time domain methods. The detailed studies include analyzing the properties of slow light when different size of the annular unit cell, and defect structures are considered, as well as exploring the buffering properties when filled polymer with different pump energies are used. Furthermore, we will fabricate high-precision samples of two-dimensional annular photonic crystal waveguides on SOI materials by employing the electron beam lithography (EBL) and inductively coupled plasma (ICP) etching techniques. The buffering parameters of these samples for the solution, such as group index and bandwidth will also be verified by using the interference measurement approach. It is believed that the present project can provide new theoretical basis and technical support for the improvement of buffering performance of two-dimensional photonic crystal waveguides.

为满足全光网络对光学元件高集成度的需求，利用二维光子晶体波导的慢光效应来发展新型全光缓存器引起了国内外学者的广泛关注。目前普通采用的二维光子晶体波导都基于单一空气孔结构，慢光的群折射率和带宽之间存在“此消彼长”的矛盾，制约了光缓存器缓存性能和动态调制效率的提高。本项目围绕一种新型的二维环形光子晶体平板波导来开展慢光缓存研究，采用有效折射率法结合平面波展开法和时域有限差分法研究二维环形光子晶体波导的结构变化和非线性填充物的折射率变化对导模色散曲线的敏感调控性能，即在不同单元尺寸、缺陷结构条件下，以及有聚合物填充时不同泵浦能量情况下的慢光特性，探索环形结构获得高群折射率和宽带宽慢光缓存器的作用机理和调节规律。采用电子束光刻技术制备出高精度的SOI基二维环形光子晶体波导样品，并采用干涉测量法验证其决定缓存性能的群折射率和带宽等参数，为提高二维光子晶体波导的慢光缓存性能提供新的理论依据和技术支持。

目前普遍采用的二维光子晶体波导都基于单一空气孔结构，慢光的群折射率和带宽之间存在“此消彼长”的矛盾，制约了光缓存器缓存性能和动态调制效率的提高。本项 目围绕一种新型的二维环形光子晶体平板波导来开展慢光缓存研究，理论上采用平面波展开法、时域有限差分法结合有效折射率近似及有效周期近似研究二维环形光子晶体的结构变化对带隙以及色散特性的调控性能，探索环形结构获得高群折射率和宽带慢光的作用机理和调节规律, 并设计各种不同的可调光缓存器；实验上采用电子束曝光和感应耦合等离子体技术制备二维环形光子晶体样品并验证其波导传输性能。主要研究结果包括：（1）发展了一种基于二维环形光子晶体波导的慢光缓存器模型，通过优化环形单元，并结合光学微流控技术，使这种缓存器具有结构紧凑，工作带宽大，缓存时间长，缓存容量大等优点；特别是在环形单元中引入各向异性介质，得到的波导对横磁模和横电模都具有宽带低色散延迟效应，是一种应用性很强的光缓存器件（发表SCI论文1篇，已申请中国发明专利1项）。（2）设计了一种以有机聚合物为基底的耦合腔波导，该波导可实现高群折射率、宽带、低色散的慢光效应，并且在不同能量的泵浦激光激发下，由于有机聚合物的非线性克尔效应，波导在保持慢光性能不降低的情况下，呈现良好的可调特性，是实现全光动态可调慢光缓存的理想模型（发表SCI论文2篇）。（3）首次研究了二维环形光子晶体的“异带”双偏振负折射效应，为未来开发基于负折射材料的宽带慢光器件提供了重要的理论基础（发表SCI论文 1篇）。（4）基于电子束光刻技术制备了近红外波段高质量二维环形光子晶体样品，通过测量透射谱验证其波导传输性能。本研究为提高光子晶体慢光缓存器性能提供了新的理论依据和技术支持，在未来全光通信中具有潜在应用价值。