基于光纤内嵌光子集成回路注入锁定的多波长窄线宽量子点激光器研究

In view of the future development of 400Gbit/s and even 1Tbit/s optical wireless communication, it is very important to study multi wavelength and narrow linewidth laser that is suitable for high order modulation format and beat frequency generation of terahertz carrier. The silicon photon chip external cavity quantum well laser is the most promising scheme for obtaining the narrow linewidth laser of kHz. But there exist some disadvantages, such as low coupling efficiency, complicated fabrication process and high cost, meanwhile the quantum well gain chip is difficult to achieve stable multimode lasing because of severe mode competition. Through cross-disciplines, a multi wavelength narrow linewidth quantum dot (QD) laser with fiber embedded photonic integrated circuits and injection locking is proposed by learning from the advantages of silicon photonic chips in multimode filtering and linewidth narrowing. We use wide gain spectrum QD gain chip to achieve stable multimode lasing, use spatiotemporal focusing technique of femtosecond laser to write the fiber embedded photonic circuit, and achieve linewidth narrowing and noise suppression by injection locking. The gain spectrum, polarization correlation, differential gain and noise index regulation of the QD gain chip, as well as the mode field constraint and regulation problem of fiber embedded photonic circuit, are studied intensively. We expect that it can achieve multi wavelength lasing with frequency difference of THz magnitude, and the output power at each wavelength ≥ 10mW, the linewidth ≤ 10kHz, RIN ≤ -145dBc/Hz.

针对未来400Gbit/s甚至1Tbit/s光载无线通信的发展需要，适用于高阶调制格式和拍频产生太赫兹载波的多波长窄线宽激光器至关重要。硅光子芯片外腔量子阱激光器是目前获取kHz量级窄线宽激光最有前景的方案。但是其存在耦合效率低、工艺复杂和成本高等弊端，而量子阱增益芯片因严重的模式竞争难以实现稳定多模激射。本项目借鉴硅光子芯片在多模滤波和线宽压窄方面的优势，通过学科交叉，创新性提出构建光纤内嵌光子集成回路注入锁定的多波长窄线宽量子点(QD)激光器。利用宽增益谱QD增益芯片，实现稳定多模激射；利用飞秒激光时空聚焦刻写光纤内嵌光子回路，通过注入锁定实现线宽压窄和噪声抑制。并深入研究QD增益芯片的增益光谱、偏振相关性、微分增益和噪声指数调控问题，光纤内嵌光子回路的模场限制和调控问题。预计可实现THz量级频率差的多波长激射，各波长输出功率≥10mW、线宽≤10kHz、RIN≤-145dBc/Hz。

针对未来400Gbit/s甚至1Tbit/s光载无线通信的发展需要，研究适用于高阶调制格式和拍频产生毫米波甚至太赫兹载波的多波长、窄线宽激光器至关重要。硅光子芯片外腔量子阱激光器是目前获取kHz量级窄线宽激光最有前景的方案。但是其存在耦合效率低、工艺复杂和成本高等弊端，而量子阱增益芯片因严重的模式竞争难以实现稳定多模激射。本项目借鉴硅光子芯片在多模滤波和线宽压窄方面的优势，创新性提出构建光纤内嵌光子集成回路注入锁定的多波长窄线宽量子点激光器。研究内容包括：外部光反馈注入锁定压窄线宽和抑制噪声机理研究；量子点有源区自组织生长及其宽增益谱调控研究；增益芯片制备及其微分增益和噪声指数调控研究；光纤内嵌光子集成回路滤波器及其注入锁定多波长窄线宽激光器研究；双折射波导Bragg光栅及其注入锁定高线偏振窄线宽混合集成激光器研究。研究结果包括：（1）研制出宽增益谱（≥100 nm）量子点增益芯片；（2）研制出局域化并联Bragg光栅阵列的光纤内嵌光子集成滤波器，及其注入锁定的多波长、窄线宽激光器。激光频率差达几百GHz，洛伦兹线宽9.4 kHz；（3）研制出高双折射波导光栅注入锁定的高线偏振、窄线宽混合集成激光器。洛伦兹线宽2.38 kHz，RIN低于-155 dBc/Hz。偏振消光比达39.6 dB，为同类型激光器最高值。基于正交偏振模式增益调控的单-双波长切换混合集成激光器，激光频率差为217 GHz；（4）研制出能量调制型切趾Bragg光栅注入锁定的抗辐射、高SMSR、窄线宽外腔量子点激光器。SMSR达66.3 dB、洛伦兹线宽13.5 kHz，激光器可承受100 krad的γ射线总辐射剂量；（5）研制出基于高阶表面光栅调制的窄线宽DBR激光器，洛伦兹线宽为70 kHz；（6）发表SCI和EI论文28篇，授权发明专利6项，培养研究生3人。上述研究阐明了多模式注入锁定的模式增益调控、线宽压窄和噪声抑制机制，阐明了增益芯片的微分增益和增益光谱调控问题，对多波长窄线宽激光器的研究具有重要的科学意义。所研制的激光器在相干光通信、空间激光通信和激光雷达等感领域具有潜在的应用价值。