基于慢光增强非线性效应的全光2R再生技术研究

All-optical regeneration technology is one of the key technologies for the future all-optical network. Conventional all-optical regenerators have drawbacks such as large-sizes, high-power consumption and non-integrable. It is difficult for them to become practical devices.To decrease the sizes and power-consumption of all-optical regenerators,we must try to enhance the material nonlinearities. However, Greater breakthrough in high nonlinear coefficients relying on materials such as sulfide is impossible.Therefore, we urgently need more effective means to enhance nonlinear effects.This project tries to introduce slow light technology into all-optical 2R regeneration. Slow light propagation in photonic crystal waveguides enhances the efficiency of nonlinear processes, opening the door for realizing all-optical 2R regenerators with small sizes and low power consumption.In this project,the physical mechanism of slow light enhancement of nonlinear effects in silicon photonic crystal waveguides will be researched, and the coupled-mode equations for slow light enhanced third-order nonlinearities including self-phase modulation,cross-phase modulation and four-wave mixing will be derived.Silicon-based photonic crystal slow light waveguides with group velocity of c/50~c/30 over 20nm bandwidth near 1.55μm wavelength region will be designed and fabricated. Making use of these photonic crystal slow light waveguides to enhance third-order nonlinearities, all-optical 2R regeneration based on self-phased modulation and offset filtering will be studied. All-optical 2R regeneration based on slow light enhanced nonlinear loss will be studied also.

全光再生技术是未来全光网络中的关键技术之一。传统全光再生器尺寸大、功耗高、不易集成，难以真正成为实用化的器件。为减小全光再生器的尺寸和功耗，必须设法增大材料的非线性系数，而依靠硫化物等材料获得高非线性系数的道路似乎走到尽头，取得更大突破的可能性不大。因此，迫切需要更有效的手段来增强非线性效应。本项目拟将慢光技术引入全光2R再生中，通过硅基光子晶体波导中的慢光效应大大增强非线性效应，从而为小尺寸、低功耗、可集成的全光2R再生器的设计和制作打开了一扇门。研究慢光增强非线性的物理机制，推导描述光子晶体波导中慢光增强三阶非线性如自相位调制、交叉相位调制和四波混频的耦合波方程；设计并制备在1.55μm波长区具有~20nm带宽、群速度在c/50~c/30范围的低损耗硅基光子晶体慢光波导；利用光子晶体波导中的慢光效应增强非线性效应，研究基于慢光增强自相位调制和偏移滤波的全光2R再生，以及基于慢光增强非线性损耗的全光2R再生。

慢光技术在光缓存、光通信、非线性光学等领域有广泛应用。在慢光的各种产生方法中，基于二维光子晶体波导的慢光具有设计灵活、慢光频率可调，以及与现有光学系统兼容性高的优点。本项目将光子晶体波导慢光技术引入全光2R再生器的设计中，研究了一种基于慢光增强非线性效应的全光2R再生方法，通过硅基光子晶体波导中的慢光效应大大增强了非线性效应，克服了传统全光再生器件尺寸大、功耗高、不容易集成的缺点。设计了在1.55μm波段具有~20nm带宽、群速度在c/30~c/20范围的硅基光子晶体慢光波导，与传统方案相比，我们的方案只改变了常规光子晶体波导的一个参数，在工艺上更容易实现。研究了光子晶体慢光波导的耦合问题。利用优化的光子晶体慢光波导进行了折射率传感研究，灵敏度达到2μm/RIU以上，表现出非常高的线性度。对基于慢光的光延时线进行了理论和实验研究，获得了最大延时量12.1ns，并在0~6ns的范围内实现了可调谐延时。对10~40GHz重复频率的主动锁模光纤激光器进行了研究，通过用方波射频信号代替传统的正弦射频信号来驱动强度调制器，成功实现了幅度均衡、脉宽较窄的有理数谐波锁模脉冲输出。对时域宽调谐的高能量方波锁模脉冲的产生进行了研究，实现了最大单脉冲能量达236.8nJ，最大时域调谐范围超过2μs。对分别基于色散平坦高非线性光纤中级联四波混频和半导体光放大器中偏振旋转效应的多波长激光器进行了研究，实现了稳定的多波长输出，光谱的覆盖范围和平整性都有了较大提高。利用光子晶体中的慢光效应增强自相位调制(SPM)效应，实现了基于慢光增强SPM和偏移滤波的全光2R再生，并完成了40Gb/s信号的全光2R再生实验。本项目的研究为小尺寸、低功耗、可集成的全光2R再生器的设计和制作打开了一扇门，对未来的全光网络和其他非线性应用具有重要意义。