Generation of a high spectral power supercontinuum covering the ultraviolet to infrared by a femtosecond laser multi-filament array in fused silica
doi: 10.37188/CO.EN-2026-0005
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摘要:
为了实现飞秒激光成丝超连续辐射的光谱参数优化，使用了透镜阵列聚焦双色飞秒激光在熔融石英块中成丝的方法产生超连续辐射。对超连续辐射光谱功率密度的提高、光谱范围的拓宽、光谱分布特性的调节等方面进行研究。首先，比较了不同波长的飞秒激光输入对成丝超连续辐射光谱范围的影响。接着，以透镜阵列替代单透镜聚焦飞秒激光成丝，通过多丝阵列形成的光谱累积效应提升超连续辐射的光谱功率密度。然后，实验比较了输入激光功率对超连续辐射光谱分布的影响，实现了对超连续辐射高频区域（或低频区域）光谱功率密度的独立控制。最后，对该方法产生的超连续辐射光谱稳定性进行了评价。实验结果表明：该方法可以获得在高频光谱范围增强的超连续辐射，并且在380 nm~950 nm的光谱范围内功率密度均高于0.1 mW/nm。该方式产生的超连续辐射可以灵活优化光谱功率密度、光谱范围和光谱分布的特性，以适应超连续辐射光谱的实际应用需求。
Abstract:Supercontinuum (SC) generated from femtosecond laser filamentation has found extensive applications due to its broadband spectral properties. In this study, we present a novel method to simultaneously improve the spectral coverage and power density of SC. This is realized by combining two-color femtosecond laser injection and multi-filament array arrangement in fused silica. With this method, high spectral power SC is obtained. The spectral power density is above 0.1 mW/nm over a broad wavelength range from approximately 380 nm to 950 nm. We find that both the spectral range and power density of SC are affected by the input power and the intensity ratio between the fundamental and second-harmonic laser pulses. In addition, the spectral fluctuation of the generated SC is measured to be less than 4% within 6 minutes. These results offer a feasible and effective way to enhance the spectral power and coverage of SC sources. They are of great importance for promoting the practical applications of SC.
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Key words:
- supercontinuum /
- filamentation /
- self-phase modulation /
- spectral cumulative effect
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图 1 实验装置。两个波长分别为800 nm和400 nm的飞秒激光脉冲通过二向色镜进行合束。组合光束使用商用10×10 MLA聚焦到熔融石英中。D：在400 nm波长处具有高反射率，在800 nm波长处具有高透射率的二向色镜
Figure 1. Experimental setup. Two femtosecond laser pulses at 800 nm and 400 nm are combined by a dichroic mirror. The combined beam is focused into fused silica using a commercial 10×10 MLA. D: dichroic mirror with high reflectivity at 400 nm and high transmission at 800 nm
图 2 (a) 400 nm和800 nm输入脉冲的光谱强度分布，以及分别由400 nm、800 nm和400+800 nm激光脉冲产生的超连续谱。 (b) 通过单透镜聚焦的双色脉冲400 nm+800 nm产生的超连续谱的光谱功率密度分布
Figure 2. (a) Spectral intensity profiles of the 400 nm and 800 nm input pulses, as well as the SC generated by the 400 nm, 800 nm and 400+800 nm laser pulses, respectively. (b) Spectral power density distribution of SC generated via two-color pulse 400 nm+800 nm focused by a single lens
图 3 (a) 多丝阵列横截面图像和(b) 对应的超连续光束。(c) 由微透镜阵列元件聚焦不同波长飞秒激光脉冲（分别为800 nm、400 nm和400 nm+800 nm）产生的超连续光谱强度分布。(d) 由单透镜和微透镜阵列分别聚焦双色脉冲产生的超连续光谱功率密度分布
Figure 3. (a) Image of the multi-filament array cross-section and (b) the corresponding SC beams. (c) SC spectral intensity profiles induced by a MLA element for femtosecond laser pulses of different wavelengths: 800 nm, 400 nm, and 400 nm+800 nm, respectively. (d)Spectral power density distributions of SC generated via two-color pulse focused by a single lens and MLA, respectively
图 4 (a) 双色飞秒激光脉冲在不同总功率P下通过微透镜阵列产生的典型超连续谱功率密度分布：功率分别为
1180 mW、932 mW、743 mW、590 mW和472 mW。(b) 超连续谱分布随激光脉冲功率的变化Figure 4. (a) Typical SC spectral power density profiles of the two-color femtosecond laser pulse passing through the MLA with different total powers P:
1180 mW, 932 mW, 743 mW, 590 mW, and 472 mW, respectively. (b) SC spectral distribution as a function of laser pulse power
图 5 通过改变输入双色激光脉冲特定组分的功率获得的高光谱功率密度超连续分布：（a）改变基频激光功率Pr（750 mW、593 mW、473 mW、375 mW、300 mW），同时固定二次谐波激光功率Pb；（b）改变二次谐波激光功率Pb（430 mW、340 mW、271 mW、215 mW、172 mW），同时固定基频激光功率Pr。
Figure 5. High-spectral-power-density SC profiles obtained by varying the power of a specific component of the input two-color laser pulse: (a) varying the fundamental frequency laser power Pr (750 mW, 593 mW, 473 mW, 375 mW, 300 mW) while fixing the second-harmonic laser power Pb; (b) varying the second-harmonic laser power Pb (430 mW, 340 mW, 271 mW, 215 mW, 172 mW) while fixing the fundamental frequency laser power Pr
图 6 我们使用双色脉冲在实验中产生的高功率超连续谱的光谱稳定性。（a）和（a'）展示了超连续中不同典型波长（380 nm、500 nm、530 nm、550 nm、600 nm、650 nm）的光谱稳定性。（b）和（c）分别描绘了通过改变基频激光功率Pr =750 mW、593 mW、473 mW和375 mW，在同一时间段内650 nm和380 nm处的光谱计数的时间演化。（d）和（e）分别展示了通过改变二次谐波激光功率Pb =430 mW、340 mW、271 mW和215 mW，在同一时间段内650 nm和380 nm处的光谱计数
Figure 6. Spectral stability of the high power SC source generated by the two-color pulse in our experiment. (a) and (a’) show the SC spectral stability of the different typical wavelengths: 380 nm, 500 nm, 530 nm, 550 nm, 600 nm, 650 nm. (b) and (c) depict the temporal evolution of the spectral counts at 650 nm and 380 nm, respectively, over the same time period by varying the fundamental laser power Pr=750 mW, 593 mW, 473 mW, and 375 mW. (d) and (e) show the spectral counts at 650 nm and 380 nm, respectively, over the same time period by varying the second-harmonic laser power Pb=430 mW, 340 mW, 271 mW, and 215 mW
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