基于短光纤循环自外差法的激光线宽测量

Laser Linewidth Measurement Based on Recirculating Self-Heterodyne Method with Short Fiber

提出了一种基于短光纤循环延迟自外差技术测量亚千赫兹激光器线宽的方法。采用延迟长度仅为2 km的循环延迟自外差干涉仪,实现了一系列不同延迟时间拍频信号的同时测量。通过仿真拟合了多组高阶拍频信号的功率谱,获得激光器的平均线宽为944 Hz,该结果与传统拍频法测得的激光线宽基本一致。所提方法不仅可以避免单次测量误差,而且能有效减小1/f频率噪声引起的频谱加宽,可精密测量窄线宽激光器的线宽。

A recirculating delayed self-heterodyne method with a short fiber is proposed for the precise measurement of sub-kHz laser linewidth.Using the recirculating delayed self-heterodyne interferometer with an only 2 km delayed fiber,a series of beat signals with different delay times are simultaneously measured.By simulating and fitting the power spectra of multiple high-order beat signals,the average linewidth of 944 Hz for a laser is obtained,which is basically in agreement with that obtained by the traditional beat frequency method.The proposed method can not only avoid a single measurement error,but also effectively reduce the frequency broadening induced by the 1/f frequency noise,therefore it can be used as an accurate detection tool for the linewidth measurement of a narrow linewidth laser.