硅基集成化可重构光学导向逻辑器件的研究

The aim of this application is to develop a reconfigurable directed logic device based on integrated micro-ring resonators (MRRs), which can be reconfigured to carry out the logic operations of XOR/XNOR and AND/NAND. Silicon submicron waveguides will be employed to compose the MRRs. Slowly varying structures will be adopted to reduce the loss and cross-talk caused by mode-mismatching at the crossing of the waveguides. Inversed tapers are integrated on the input and output terminals of the waveguides to reduce the mode-mismating between the waveguides and the fibers to enhance the coupling efficiency. The plasma dispersion effect in silicon will be employed to modulate the MRR at a high speed. The physical model of the doping and modulating area will be established, through which the electrical parameters of the device will be extracted. The doping concentration and the dimensions of the electrodes will be optimized using the electromagnetic simulation software, which will result in the characteristics of higher bandwidth, impedance matching and the matching of the doping area and the optical field distribution. The performance of the device will be improved in terms of the mulation efficiency and the working speed, resulting in lower operating voltage and power dissipation. Reconfigurable directed logic devices with the above-mentioned features will be fabricated in a CMOS-compatible process. The reconfigurable optical directed logic devices proposed in this application have several advantages over traditional ones. They can be made by a process compatible with those used in modern microelectronics industry, resulting in obvious merits such as small volume, low power-consumption, and good scalability. They can also be readily to be integrated with electrical components to form a silicon monolithic integrated multi-functional information processing system.

本申请拟采用一种集成光学元件- - 微环谐振器，来实现可完成"异或/同或"及"与/与非"逻辑运算的可重构光学导向逻辑器件。硅基微纳波导将被用来制作微环谐振器。波导交叉节点将采用缓变结构来减小由于模场不匹配引起的损耗和串扰。波导输入/输出端将采用倒锥型结构来减小波导与光纤的模场失配，从而提高耦合效率。硅的等离子色散效应将被用于微环谐振器的高速调制。将建立掺杂调制区物理模型，提取出器件电学参数。结合电磁场仿真软件来优化掺杂浓度和电极结构，提高器件带宽，实现阻抗匹配及掺杂区与光场分布区域的匹配，从而提高器件的调制效率与工作速度，使其具有低工作电压与功耗。本申请将最终利用CMOS兼容工艺制作出可重构光学导向逻辑器件。与传统光逻辑器件相比，本申请拟研究的基于硅基微环谐振器的光学逻辑器件制造工艺与现有微电子工艺兼容，器件体积小、功耗低、易扩展，便于和电学元件集成，有望实现硅基单片集成的多功能信息处理系统。

片上多核处理器成为处理器架构主流的事实说明，依靠减小晶体管尺寸、提高工作频率的手段提高微处理器性能的方式已经遇到了困难，摩尔定律已经接近失效。在这种局面下，针对光网络交换节点的需求研究开发新型信息处理方式已经成为普遍的共识。本项目的主要目的是深入研究一种称为“导向逻辑”的新型光信息处理手段。导向逻辑的概念最初是由美国科学家James Hardy和以色列科学家Joseph Shamir于2007年提出的，它的基本思想是利用逻辑操作数来控制光子回路中光波的传播路径，而将逻辑运算结果表现在输出端口的出光状态上。导向逻辑利用光开关来控制光的传播，有两个显著特征与优点：一是逻辑操作数对光开关的作用是同时完成的，这有别于传统电学逻辑中后级晶体管需要等待前级电路的运算结果；二是运算过程依赖于光的传播特性，天然具有高带宽与低延迟的特点。导向逻辑器件的基本要素是实现光信号路径切换的光开关。光开关的实现方式有很多，本项目要研究的是一种硅基光子学的实现方案——基于硅基微纳波导微环谐振器（MRR, Micro-Ring Resonator）的光开关。由于采用硅材料作为器件实现平台，这种方案的优点在于工艺成熟、集成度高以及可实现光电混合集成。本项目的主要工作即是对基于硅基微纳波导MRR光开关的可重构导向逻辑器件进行原理性验证，并在MRR光开关特性的研究基础上评估所提出的导向逻辑器件的性能。本项目的主要考核指标为：波导的交叉损耗小于0.5 dB/节点；波导与光纤的耦合损耗小于3 dB/端面；在SOI 片上实现可重构光学导向逻辑器件，实现每秒2 亿次XOR、XNOR、AND及NAND 运算。经过三年的研究，上述指标均已实现。