基于反Stokes种子增强的新型四波混频中红外光纤激光器研究

Mid-infrared lasers have important applications and unprecedented demands in the biomedical, molecular spectroscopy, homeland security, environmental monitoring and other fields. A brand new method which can enhance four-wave mixing by injecting an anti-Stokes seed light is proposed for developing a compact, stable all-optical mid-infrared fiber lasers in fluoride single mode fiber pumped by near-infrared lasers. In this research project, we mainly focus on the study of the conditions and the corresponding factors of emitting mid-infrared laser through four-wave mixing. The various factors which influent the efficiency of the infrared laser are studied and the physical mechanism of four-wave mixing enhanced by the anti-Stokes seed is analyzed. The variation of pulse width of output infrared laser and the capability of wavelength tuning is also studied. The study of the project will help to achieve an all-fiber, high-efficiency, tunable mid-infrared pulsed laser in mid-infrared fiber without the infrared optical elements such as fiber grating and mode-locking elements, which provides a new way of developing mid-infrared fiber lasers.

中红外激光器在生物医学、分子光谱学、国土安全、环境监测等领域具有重要的应用前景和空前的市场需求。本项目以发展结构紧凑、性能稳定的全光纤中红外激光器为目标，提出一种新的四波混频增强方法——反Stokes种子光注入增强四波混频，通过近红外激光泵浦，在氟化物单模光纤产生中红外激光输出。项目主要研究氟化物光纤中通过四波混频产生中红外激光的条件和各种影响因素；研究影响中红外激光效率的各种因素，并分析反Stokes种子光注入增强四波混频的物理本质；分析并研究中红外激光器输出脉宽的变化及波长调谐能力。本项目的研究将实现全光纤、高效率、可调谐的中红外脉冲激光输出，而无需光栅以及锁模元件等中红外光学器件，这为中红外光纤激光器的研制提供一种新的思路。

中红外光纤激光器与传统的固体激光相比较，具有结构紧凑、性能稳定以及免维护等优点，在在生物医学、国土安全等领域具有重要的应用前景和空前的市场需求。本项目围绕采用光纤中非线性变频技术，实现近红外激光到中红外激光的转换，主要工作包括：（1）建立理论模型，通过数值模拟，研究高效FWM以及通过非线性频率变换产生中红外激光的条件以及反Stokes 种子光增强FWM的物理机理；（2）研制位于近红外波段的脉冲激光和可调谐激光，实验论证反Stokes信号光和Stokes信号光的加入，对FWM过程的促进作用；（3）通过非对称熔接的技术方案，实现了石英光纤与氟化物光纤的高强度、低损耗熔接，在此基础上，通过非线性频率变换，在全光纤结构中实现了近红外激光产生宽光谱范围的中红外激光输出。通过项目的研究，从理论和实验上论证了Stokes种子光或反Stokes 种子光的加入，能有效增强FWM过程，并通过非线性频率变换的方法，实现了中红外激光的产生，具有重要的意义。