Fang Zhiwei, Pu Guoqing, Luo Chao, Wang Jiajin, Hu Weisheng, Yi Lilin
Opt Express. 2025 Jul 28;33(15):32827-32837. doi: 10.1364/OE.568440.
The repetition frequency difference in the dual-comb light source is critical for balancing measurement accuracy and refresh rate in high-precision ranging and spectroscopy. The single cavity dual-wavelength mode-locked fiber laser (MLFL) based on a birefringent filtering mechanism can produce the dual-comb regime (DCR) through dedicated cavity designs and careful tuning of birefringent filter characteristics (e.g., central wavelength, spectral separation, and modulation depth). However, achieving automatic, on-demand tuning of the repetition frequency difference of DCR in the MLFL is challenging. In this work, we demonstrate, on-demand DCR generation with a specified repetition frequency difference in an MLFL usinging a spectral seeker. A programmable optical filter combined with time-stretch dispersive Fourier transform enables real-time spectral acquisition with absolute wavelength accuracy. Subsequently, reinforcement learning tunes the polarization state of the electric polarization controller inside the cavity in real time to optimize the birefringent filter, thereby generating the DCR with the target emission wavelength corresponding to a desired repetition frequency difference. Thus, on-demand DCR generation is achieved by controlling the emission wavelength of one of the dual combs, which spans from 1528 nm to 1539 nm, thereby adjusting the repetition frequency difference from 162 Hz to 212 Hz. Furthermore, the mean time for automatic DCR generation (i.e., from free-running state to the desired DCR) is 0.407s, which is ∼6 times faster than the state of the art. The intelligent MLFL continuously operates under the DCR for over 12 hours, exhibiting outstanding stability. The demonstrated on-demand DCR generation with real-time control represents a magnificent step towards utilizing the single cavity dual-comb source in diverse applications, such as high-precision ranging and spectroscopy.
双梳状光源中的重复频率差对于在高精度测距和光谱学中平衡测量精度和刷新率至关重要。基于双折射滤波机制的单腔双波长锁模光纤激光器（MLFL）可以通过专门的腔设计和对双折射滤波器特性（如中心波长、光谱间隔和调制深度）的精细调谐来产生双梳状 regime（DCR）。然而，在MLFL中实现DCR重复频率差的自动、按需调谐具有挑战性。在这项工作中，我们展示了使用光谱寻迹器在MLFL中按需产生具有指定重复频率差的DCR。一个可编程光学滤波器与时间拉伸色散傅里叶变换相结合，能够以绝对波长精度进行实时光谱采集。随后，强化学习实时调整腔内电光偏振控制器的偏振状态，以优化双折射滤波器，从而产生具有与所需重复频率差相对应的目标发射波长的DCR。因此，通过控制双梳之一的发射波长来实现按需DCR产生，该发射波长范围从1528nm到1539nm，从而将重复频率差从162Hz调整到212Hz。此外，自动产生DCR的平均时间（即从自由运行状态到所需DCR）为0.407秒，比现有技术快约6倍。智能MLFL在DCR下连续运行超过12小时，并表现出出色的稳定性。所展示的具有实时控制的按需DCR产生代表了在将单腔双梳状源应用于各种应用（如高精度测距和光谱学）方面迈出的重要一步。
