基于1μm/1.5μm双波段脉冲光纤激光器的超宽带超连续谱光源研究

The ultra-wideband and flat spectrum is the key object for the research of supercontinuum (SC) generation. Traditionally, the supercontinuum is mainly generated from a single-material fiber pumped by a single-band fiber laser from the 1 μm or the 1.5 μm fiber lasers. This technique greatly restricts the synchronous spectrum extension of the output supercontinuum on the short wavelength of visible light and the long wavelength of mid-infrared (MIR) band, as well as the adjustment of the spectral flatness. In this project, a novel 1 μm/1.5 μm dual-band pulsed fiber laser is first proposed based on the Er/Yb co-doped fiber amplifier, and then adopted to pump a cascaded-fiber composed of a silicon PCF and a fluoride fiber. The dual-band outputs from the fiber laser correspond to the optimal pump-wavelength regions of the two fibers with different materials. Consequently, the output SC from the cascaded-fiber could be expanded to both the visible wavelengths and the MIR wavelengths. The output powers and wavelengths of the MOPA-structured dual-band fiber laser could be varied through the two seed lasers, accordingly, flat spectrum also could be obtained. Therefore, we propose an in-depth study of the characteristics and mechanisms of the dual-band pulsed fiber laser and the supercontinuum generated from the cascaded-fiber, which enables an all-fiber ultra-wideband and flat supercontinuum source. This study will provide an effective solution for the extensive demand of ultra-wideband light sources from a wide range of applications, including air pollution detection ,biomedical research, military fields, to name a few.

超宽带高平坦光谱是超连续谱研究的核心目标。目前产生超连续谱的主流技术是采用1μm或1.5μm某一波段的高功率光纤激光器泵浦某一材质的光纤，然而单一波段激光泵浦单一材质光纤的技术导致超连续谱难以在可见光和中红外波段同时扩展，限制了超宽带光谱的实现，且光谱平坦度也难以控制。 针对这些局限，本项目首次提出利用Er/Yb共掺光纤放大器构建1μm/1.5μm双波段脉冲光纤激光器，进而泵浦石英光子晶体光纤和氟化物光纤组成的级联光纤来产生超连续谱。两个激光波段分别对应两种材质光纤的最佳泵浦区，有利于产生从可见光到中红外波段的超宽带光谱；两波段的输出功率和波长可通过种子源进行调整，有利于获得高平坦光谱。 基于此，项目将研究双波段脉冲光纤激光器及其泵浦级联光纤产生超连续谱的特征和机理，进而研制高功率超宽带高平坦超连续谱光源。本研究将为大气污染检测、生物医疗以及军事等领域对超宽带光源的需求提供有效的解决思路。

本项目研究了1 μm和1.5 μm双波段脉冲光纤激光器种子源，1 μm和1.5 μm双波段高功率脉冲光纤激光器，进而进行多波段脉冲激光泵浦的超宽带超连续谱研究。. 1. 双波段脉冲种子源方面：研究实现了1 μm 波长可调谐、脉宽可调谐耗散孤子锁模光纤激光器以及双波长可调谐耗散孤子光纤激光器；研究实现了1.5 μm高能量矩形脉冲耗散孤子锁模光纤激光器和1.5 μm波长可调谐、脉宽可调谐锁模光纤激光器；首次研究实现了基于单一增益光纤的1 μm /1.5 μm 双波段方波脉冲锁模光纤激光器，以及1 μm /1.5 μm 双波段同步调Q和锁模脉冲光纤激光器。. 2. 高功率双波段脉冲光纤激光器方面：研究实现了1 μm高功率百瓦级全光纤化波长可调谐皮秒脉冲光纤激光器和平均功率达到42W的1.5 μm全光纤化单模纳秒脉冲光纤激光器，进而实现了基于单一增益介质的1 μm /1.5 μm 高功率双波段脉冲光纤激光器。. 3. 在超宽带超连续谱产生方面，研究实现了ZBLAN光纤和常规石英光纤的高效率熔接耦合；在多波段脉冲激光器泵浦下实现了全光纤化超宽带超连续谱光源，可见光－近红外波段光谱范围覆盖450 nm-2.2 μm，近红外－中红外波段光谱覆盖1.9-4.1 μm。. 这些研究工作共发表SCI学术论文12篇，申请发明专利4项，获得2项发明专利授权和4项实用新型专利授权。