Zhang Liang, Chen Liang, Bao Xiaoyi
Opt Express. 2020 Mar 2;28(5):6719-6733. doi: 10.1364/OE.387185.
Laser with high spectral purity plays a crucial role in high-precision optical metrology and coherent communication. Thanks to the rapid development of laser frequency stabilization, the laser phase noise can be remarkably compensated, allowing its ultra-narrow linewidth subject to mostly quantum limit. Nevertheless, the accurate characterization of phase noise statistics and its linewidth of a highly coherent laser remains ambiguous and challenging. Here, we present an approach capable of revealing delay-time-resolved phase noise statistics of a coherent laser based on coherent optical time domain reflectometry (COTDR), in which distributed Rayleigh scattering along a delay fiber essentially allows a time-of-flight mapping of a heterodyne beating signal associated with delay-time-dependent phase information from a single laser source. Ultimately, this novel technique facilitates precise measurement of ultra-narrow laser linewidth by exploiting its delay-time-resolved phase jitter statistics of random fiber laser with pump lasers of various linewidths, confirmed with the analytical modeling and numerical simulations.
具有高光谱纯度的激光在高精度光学计量和相干通信中起着至关重要的作用。由于激光频率稳定技术的快速发展，激光相位噪声可以得到显著补偿，使其超窄线宽大多受限于量子极限。然而，对于高相干激光的相位噪声统计及其线宽的精确表征仍然不明确且具有挑战性。在此，我们提出一种基于相干光时域反射仪（COTDR）的方法，该方法能够揭示相干激光的延迟时间分辨相位噪声统计，其中沿延迟光纤的分布式瑞利散射本质上允许对与来自单个激光源的延迟时间相关相位信息相关的外差拍频信号进行飞行时间映射。最终，通过利用具有各种线宽泵浦激光器的随机光纤激光器的延迟时间分辨相位抖动统计，这种新技术有助于精确测量超窄激光线宽，并通过分析建模和数值模拟得到了证实。
