面对模拟通讯应用的被动反馈高速直调DFB激光器研究

High-speed analog communication system such as K-band (18 GHz ~ 26.5 GHz) phased array radar has put forward more and more demanding on the performance of the directly modulated semiconductor lasers. It requires directly modulated laser with broaden 3dB small-signal modulated bandwidth (3dB-MB) and flatten the modulation frequency response (MFR) curve. However, the conventional DFB laser is difficult to meet the stringent requirements. To respond to the challenge, we propose a novel DFB laser chip with integrated passive feedback section to improve its 3dB-MB, and a new packaging design with microwave transmission line based on fractal structural microwave photonic crystal to suppress electron-photon resonance and photon -photon resonance and flatten the response curve by their selective restrain effect. The research content includes: (1) Mechanism and optimization of the 3dB-MB broadening caused by photon -photon resonance in passive feedback DFB laser. (2) Analysis and optimization of the microwave transmission line with fractal geometry to form some selected electromagnetic band gaps and special microwave reflection characteristic, and its application in suppress MFR peak.(3) With the optimization of epitaxial materials, the device design and fabrication, the package design and process, high-speed lasers with flat response curve can be fabricated finally. Its 3dB-MB can reach 27GHz. The breakthrough of this key photoelectric component is expected to drive the rapid development of high-speed analog communication related fields and also has a positive impact on the next-generation wireless communication system and national defense technology.

K波段（18～26.5GHz）相控阵雷达等高速模拟通讯应用系统对直接调制半导体激光器的性能的要求越来越高，目前常规的激光器难以同时满足拓宽小信号3dB调制带宽和平坦化调制响应曲线的要求。为达到这些指标，本项目提过通过单片集成带有新型被动光反馈单元的DFB激光来展宽器调制带宽，采用光子晶体理念设计的分形结构传输线来选择性抑制电子-光子和光子-光子的振荡峰来实现激光模块响应曲线的平坦化。内容包括：新型反馈单元引入光子-光子共振峰实现的调制带宽拓展机理与应用；分形几何特征微波传输线对应的电磁波带隙、微波反射特性及其在振荡峰抑制等方面的恰当应用；通过材料外延优化、器件设计与工艺、封装设计与工艺的协同配合，研制出具有平坦响应曲线，小信号调制3dB带宽达到27GHz的高速激光器。该关键元器件的突破有望带动高速模拟通讯相关领域的迅速发展，对下一代无线通讯和国防事业都有积极作用。

高线性的微波激光器在高速模拟通讯应用中作为核心光源越来越受到重视，为了将微波激光器拓展到K波段（18～26.5GHz）使用，需要拓宽DFB激光器芯片的小信号3dB调制带宽和平坦化调制响应曲线。应对该问题本项目通过材料优化系统研究了量子阱外延材料和结构设计对带宽的影响，研制出了带宽大于27GHz的DFB微波激光器芯片，并对其微波特性如噪声、二次谐波、交调特性等进行了系统的表征；探索了通过单片集成两段式激光器来实现带宽拓展的机制，重点研究了由DFB-DBR组成的DR激光器的光子-光子振荡机制，采用AlGaInAs量子阱材料研制出的DR激光器，基于光子-光子振荡机制实现了带宽拓展，带宽达到了27GHz；研究了周期性微结构对共面波导微波传输的影响，通过微结构的微波反射特性和谐波抑制特性，实现了较好的微波传输特性的控制，并将其应用在激光器的调制响应曲线平坦度优化上，对比了其对电子-光子振荡特性和光子-光子振荡特性的作用效果，发现其对电子-光子振荡响应的叠加作用非常明显。