基于飞秒激光诱导双折射波导光栅反馈的窄线宽半导体激光器研究

To fulfill the increasing demands on data transmission speed and transmission distance for the space coherent laser communication, it becomes an key issue to obtain kHz-scale narrow linewidth laser terminals with compact structure, low cost, low energy consumption and high coherence. The technique of the external cavity feedback semiconductor laser is regarded as the most promising solution to achieve the ultranarrow linewidth and linear polarization. The existing related studies mainly focus on the feedback light injection by diffraction gratings and microdisk resonators, which have the drawbacks of low efficiency, low integration level and poor stability. In order to solve these problems, we propose a novel narrow linewidth semiconductor laser based on femtosecond-laser-fabricated silicon-based waveguide Bragg grating (WBG) reflectors with high birefringence. This work will be carried out on the basis of the mechanisms on narrowing the linewidth, locking the mode, reducing frequency feedback noise by WBG light feedback, and femtosecond-laser-induced generation of stress and form birefringence. The high birefringence WBG has selectivity of the main polarization of the gain chip to realize linear polarization. This novel device is expected to implement the C-waveband highly linear polarized laser output with the linewidth ≤ 10 kHz, side-mode suppression ratrio ≥ 40 dB and relative intensity noise ≤ -150 dB/Hz. This project will extend the applications of the femtosecond laser processing in semiconductor laser field and provide a competitive laser source for space coherent laser communication.

针对空间相干激光通信对数据传输速率和传输距离不断增加的需求，紧凑型、低成本、低能耗和高相干性的kHz量级窄线宽激光终端的研究成为关键。外腔反馈半导体激光器成为获取极窄线宽和线偏振激光最有前景的方案。现有研究主要集中在衍射光栅、微盘谐振腔提供反馈光注入，这些激光器存在效率低、集成度低和稳定性差的弊端。针对此问题，本项目创新性提出构建基于飞秒激光制备高双折射硅基波导Bragg光栅（WBG）反馈的窄线宽半导体激光器。该工作将在WBG光反馈压窄线宽、锁模和降低频率噪声机理，以及飞秒激光诱导应力和形状双折射机理的研究基础上开展；高双折射WBG对增益芯片主偏振具有选择性，以获得线偏振激光。预计该新颖器件可实现线宽≤10 kHz、边模抑制比≥40 dB、相对强度噪声≤-150 dB/Hz的C波段高线偏振激光。本项目的研究将拓展飞秒激光在半导体激光器领域的应用，并为空间相干光通信提供有竞争力的激光光源。

针对空间相干激光通信对数据传输速率和传输距离不断增加的需求，紧凑型、低成本、低能耗和高相干性的kHz量级窄线宽激光终端的研究成为关键。外腔反馈半导体激光器成为获取极窄线宽和线偏振激光最有前景的方案。现有研究主要集中在衍射光栅、微盘谐振腔提供反馈光注入，这些激光器存在效率低、集成度低和稳定性差的弊端。针对此问题，本项目创新性提出了构建基于飞秒激光制备高双折射硅基波导Bragg光栅（WBG）反馈的窄线宽半导体激光器。具体开展的研究包括：外部光反馈注入锁定压窄线宽和抑制噪声机制研究；高双折射、窄带宽波导Bragg光栅的设计和制备研究；C波段高微分增益InP基多量子阱半导体增益芯片研究；波导光栅外腔光反馈注入锁定的窄线宽半导体激光器研究；基于多谢振峰Bragg光栅注入锁定的多波长窄线宽半导体激光器探索性研究。最终，研制出了标准蝶形封装和模块化驱动电路封装的kHz量级窄线宽半导体激光器。其主要性能包括：激光波长1550±1 nm，输出功率11.71 mW@100 mA，边模抑制比（SMSR）51.0 dB，偏振消光比（PER）20.66 dB，波长温度系数约10 pm/℃，最小洛伦兹线宽小于1 kHz，积分线宽小于10 kHz@1 ms，最小相对强度噪声（RIN）达-150 dBc/Hz。在上诉研究中，共发表SCI论文9篇，EI和核心论文5篇，申请发明专利2项，协助培养研究所3名。上述研究结果阐明了外部光反馈注入压窄线宽和抑制噪声的机制，拓展了飞秒激光微纳加工技术在半导体激光器研究领域的应用。本项目所研制的紧凑型、高光谱特性和低噪声的kHz量级窄线宽半导体激光器为空间相干光通信提供了具有竞争力的激光光源。