基于短光纤延时自外差的可见光单频激光线宽测量方法  

Linewidth Measurement of Visible Single-Frequency Laser Based on Short-Fiber Delay Self-Heterodyne

作　　者：王进[1,2] 杨振营 李丰芮 单小琴 郑光金[3] 韩正英 韩志刚[1,2] 朱日宏[1,2] Wang Jin;Yang Zhenying;Li Fengrui;Shan Xiaoqin;Zheng Guangjin;Han Zhengying;Han Zhigang;Zhu Rihong(School of Electronic and Optical Engineering,Nanjing University of Science&Technology,Nanjing 210094,Jiangsu,China;MIIT Key Laboratory of Advanced Solid Laser,Nanjing University of Science&Technology,Nanjing 210094,Jiangsu,China;The 41st Research Institute of China Electronics Technology Group Corporation,Qingdao 266555,Shandong,China)

机构地区：[1]南京理工大学电子工程与光电技术学院,江苏南京210094 [2]南京理工大学先进固体激光工信部重点实验室,江苏南京210094 [3]中国电子科技集团公司第四十一研究所,山东青岛266555

出　　处：《光学学报》2023年第21期164-173,共10页Acta Optica Sinica

基　　金：国家自然科学基金(61875087)。

摘　　要：提出一种基于短光纤延时自外差法的可见光波段单频激光线宽测量方法,利用短延时光纤减小可见光在石英光纤中的损耗并降低系统低频噪声,通过频谱信号平滑方法极大地提高频谱数据的信噪比,通过非线性最小二乘法拟合还原原始信号频谱,并最终计算出可见光波段激光线宽。构建可见光波段的延时自外差测量系统,搭建127 m和500 m延时光纤的可见光波段延时自外差测量装置,测得635 nm单频外腔半导体激光器线宽为29.4 kHz,与两个相同型号激光器互拍的测量结果接近,证明了基于短光纤延时自外差方法测量可见光单频激光器线宽的可行性。Objective Visible single-frequency lasers have important applications in optical precision measurement and frequency standards.As an important parameter to determine laser coherence,linewidth guarantees the contrast of spatial interference fringes and directly determines the accuracy of the measurement system.In the visible light band,common measurement methods for laser linewidth are employing spectrometers and F-P cavities,but the measurement accuracy of these methods can only reach GHz and MHz levels,which cannot meet the current requirements of kHz or even Hz levels for linewidth measurement accuracy.As a new linewidth measurement method,the short-fiber delay self-heterodyne method can realize kHz linewidth measurement in communication bands,but the applications in visible light bands are rarely studied.Since the short-fiber delay self-heterodyne method can obtain high-precision linewidth without adopting too long optical fiber,it is a potential means to measure the laser linewidth in visible light bands.Methods We propose a measurement method of visible single-frequency lasers based on the short-fiber self-heterodyne method,which introduces the short-fiber delay self-heterodyne method in the communication bands into the visible light bands and realizes linewidth measurement of high-precision lasers in the visible light bands.The principle of the proposed method is that the laser beams are split by the beam splitter(BS),one path is time-delayed by the delay fiber,and the other path's frequency is shifted by the acousto-optic modulator(AOM).The two laser beams are combined by a beam combiner(BC)to obtain a beat signal.Since the optical path difference introduced by the delay fiber is much smaller than the laser coherence length,an interference envelope will appear around the center frequency in the spectrum of the beat frequency signal,and the sidelobe of the envelope contains the laser linewidth information.We design a short-fiber delay selfheterodyne optical path as shown in Fig.1 to interpret the sidelobes

关 键 词：测量 线宽测量 延时自外差法 可见光激光器 光学系统 

分 类 号：O436[机械工程—光学工程]