Nonlinear frequency conversion of wavelength agile and high-power random fiber lasers can provide a promising way to generate continuous-wave (CW) visible and mid-infrared (MIR) light with unique properties such as the continuous modeless spectrum, low temporal/spatial coherence, and high temporal stability. Here, we report a dual-wavelength switchable and tunable random Raman fiber laser (RRFL) based on a phosphosilicate fiber that has two Raman gain peaks for the first time and demonstrate its superior capability to generate widely tunable CW visible and mid-infrared light via nonlinear frequency conversions. By using the combination of a tunable pump and two tunable gratings in Littrow configuration that can provide separated point feedback for the two Stokes wavelengths corresponding to silica- and phosphorus-related Raman peaks, the spectrum of an RRFL can be flexibly manipulated for the aim of nonlinear frequency conversions, including single-wavelength tunable emission at the 1.1 μm or 1.2 μm band for second-harmonic generation (SHG), dual-wavelength simultaneously tunable emission at the 1.1 μm and 1.2 μm bands for the sum-frequency generation (SFG), and dual-wavelength separation tunable emission for difference-frequency generation (DFG). As a result, with the combination of SHG and SFG in a periodically poled lithium niobate crystal array, we experimentally demonstrate the broadest tuning range (560–630 nm) of visible light generated from an RRFL, to the best of our knowledge. The tunable MIR light in the range of 10.7–12.3 μm is also demonstrated through DFG of an RRFL operating in separation tunable dual-wavelength emission mode in a BaGa4Se7${\mathrm{BaGa}}_4{\mathrm{Se}}_7$ (BGSe) crystal, which is the first realization of >10 μm$>10\mathrm{\mu m}$ CW DFG in the BGSe crystal. We believe the developed dual-wavelength switchable and tunable RRFL can provide a new compact, robust, and cost-effective platform to realize broadly tunable light in both the visible and MIR regions, which can also find potential applications in imaging, sensing, and temporal ghost imaging in various spectral bands.

中文翻译：

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基于双波长可切换和可调谐随机拉曼光纤激光器的广泛可调连续波可见光和中红外光产生

波长捷变和高功率随机光纤激光器的非线性频率转换可以提供一种有前途的方法来产生连续波 (CW) 可见光和中红外 (MIR) 光，这些光具有连续无模光谱、低时间/空间相干性等独特特性和高时间稳定性。在这里，我们报告了一种基于磷硅酸盐光纤的双波长可切换和可调谐随机拉曼光纤激光器 (RRFL)，该激光器首次具有两个拉曼增益峰，并展示了其产生广泛可调 CW 可见光和中红外光的卓越能力非线性频率转换。通过在利特罗配置中使用可调谐泵浦和两个可调谐光栅的组合，可以为对应于二氧化硅和磷相关拉曼峰的两个斯托克斯波长提供分离的点反馈，可以灵活地操纵 RRFL 的频谱以实现非线性频率转换，包括在 1.1 μm 或 1.2 μm 波段的单波长可调谐发射以产生二次谐波 (SHG)，在 1.1 μm 的双波长同时可调谐发射用于和频生成 (SFG) 的 1.2 μm 波段，以及用于差频生成 (DFG) 的双波长分离可调谐发射。因此，通过在周期性极化铌酸锂晶体阵列中组合 SHG 和 SFG，我们通过实验证明了 RRFL 产生的可见光的最宽调谐范围（560-630 nm），据我们所知。10.7-12.3 μm 范围内的可调谐 MIR 光也通过在分离可调谐双波长发射模式下运行的 RRFL 的 DFG 在BaGa 4 Se 7${\mathrm{BaGa}}_4{\mathrm{Se}}_7$ (BGSe) 晶体，这是在 BGSe 晶体中首次实现>10μm $>10\mathrm{\mu m}$我们相信所开发的双波长可切换和可调谐 RRFL 可以提供一个新的紧凑、稳健且具有成本效益的平台，以在可见光和中红外区域实现广泛可调光，也可以在成像、传感和时间方面找到潜在的应用各种光谱带中的鬼成像。