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

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。

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.