Duan Yuhua, Dong Xin, Zhang Lei, Li Yaoshuai, Lei Zihui, Chen Liao, Zhou Xi, Zhang Chi, Zhang Xinliang
Opt Express. 2019 Feb 4;27(3):2621-2631. doi: 10.1364/OE.27.002621.
An inertial-free, ultrafast frequency comb source based on two chirped optical frequency combs (OFCs) is proposed and experimentally demonstrated. The high linearity frequency sweeping is realized by the Vernier effect between the two OFCs rather than any mechanical motion component, so that good stability and reliability are ensured and no recalibration or resampling process is required. Swept rate up to 1 MHz is realized while keeping a narrow instantaneous linewidth of 0.03 nm, thanks to the extra-cavity frequency sweeping method. The wavelength step is proportional to the swept rate (3.8 pm at 10 kHz), and can be tuned by changing the repetition rate difference between the two OFCs. This swept source is applied for high-speed wavelength encoded imaging and achieves 4.4-μm spatial resolution at a 329-kHz frame rate. Compared with the traditional time-stretch microscopy, the signal acquisition bandwidth decreased from 3.8 GHz to below 90 MHz to achieve the same spatial resolution. Furthermore, the exposure time for a specific wavelength is much longer due to the discrete sweeping feature, which is a benefit for higher sensitivity. This discrete swept source provided a promising low-cost option for high-speed biomedical imaging systems and high-accuracy spectroscopy.
提出并通过实验证明了一种基于两个啁啾光学频率梳（OFC）的无惯性、超快频率梳源。两个OFC之间的游标效应实现了高线性频率扫描，而不是任何机械运动部件，从而确保了良好的稳定性和可靠性，并且不需要重新校准或重新采样过程。由于腔外频率扫描方法，在保持0.03 nm的窄瞬时线宽的同时，实现了高达1 MHz的扫描速率。波长步长与扫描速率成正比（10 kHz时为3.8 pm），并且可以通过改变两个OFC之间的重复率差来调谐。这种扫描源应用于高速波长编码成像，并在329 kHz的帧率下实现了4.4μm的空间分辨率。与传统的时间拉伸显微镜相比，信号采集带宽从3.8 GHz降低到90 MHz以下，以实现相同的空间分辨率。此外，由于离散扫描特性，特定波长的曝光时间长得多，这有利于提高灵敏度。这种离散扫描源为高速生物医学成像系统和高精度光谱学提供了一种有前景的低成本选择。
