物理学报2024，Vol.73Issue(1)：113-120,8.DOI:10.7498/aps.73.20231049
基于光学反馈频率锁定的窄线宽稳定中红外激光产生技术研究
Research on generation of stable mid-infrared lasers with narrow linewidths based on optical feedback locking
摘要
Abstract
Mid-infrared precision spectroscopy has important applications in the fields of trace gas detection and the determination of fundamental physical constants.However,due to the limited commercialization of related technologies,there is a lack of narrow linewidth laser sources or linewidth narrowing approaches in the mid-infrared region,as well as stable mid-infrared frequency standards.The most commercialized and widely used mid-infrared laser source is the quantum cascade laser(QCL).But its free-running linewidth is more than MHz scale due to the influence of laser drive current noise and temperature fluctuation.This impedes the development of precision spectroscopy in this region.In this work,we introduce a technique for generating a narrow linewidth,stable mid-infrared laser by using optical feedback frequency locking,with a high-finesse mid-infrared ultrastable Fabry-Pérot cavity as the frequency reference.The optical cavity consists of two high reflectivity mirrors separated by ultra-low expansion(ULE)material with a low temperature expansion coefficient,and its temperature is precisely controlled.And the cavity is also surrounded in a vaccum cavity made of stainless steel.All these measures ensure the cavity length and its longitudinal mode stability.By using optical feecback,a QCL is locked to the cavity,which stabilizes the laser frequency and narrows the laser linewidth.In order to improve the long-term stability of the optical feedback,an active servo is leveraged to control the feedback phase.The error signal for the servo is obtained by using the method similar to the Pound-Derver-Hall locking.In this work,we first theoretically analyze the feasibility of laser to F-P cavity frequency locking by optical feedback.We propose the laser frequency response model with a linear F-P cavity under optical feedback,and analyze the influence of the direct cavity reflection on the laser frequency.Then the experimental demonstration is conducted.Firstly,we measure the reflectivity of the cavity mirror by using cavity ring-down spectroscopy,resulting in a cavity finesse of 30200 and a cavity mode linewidth of 49.7 kHz.After that,we successfully achieve optical feedback frequency locking,and consecutive cavity transmission is observed.The error signal for the control of the optical feedback phase is used to evaluate the locking performance by converting it into the laser frequency noise.By analyzing the noise spectral density,the QCL linewidth is narrowed to 0.3 Hz on a short timescale(<10 ms).And the long-term stability is suspected to be dedicated by the temperature variation of the optical cavity,resulting in a laser frequency drift 20 kHz/12 h.The narrow linewidth stabilized mid-infrared laser source obtained with this technique is expected to serve as an effective frequency reference source for mid-infrared precision spectroscopic measurements.关键词
激光频率锁定/中红外激光/线宽压窄/光学反馈Key words
laser frequency locking/mid-infrared laser/linewidth narrowing/optical feedback引用本文复制引用
杨家齐,赵刚,焦康,高健,闫晓娟,赵延霆,马维光,贾锁堂..基于光学反馈频率锁定的窄线宽稳定中红外激光产生技术研究[J].物理学报,2024,73(1):113-120,8.基金项目
国家重点研发计划(批准号:2022YFC3700329)、国家自然科学基金(批准号:61905134,61905136,62175139)和山西省留学人员科技活动项目(批准号:20220001)资助的课题.Project supported by the National Key R&D Program of China(Grant No.2022YFC3700329),the National Natural Science Foundation of China(Grant Nos.61905134,61905136,62175139),and the Advanced Funding Project for the Scientific Research of the Returned Overseas Chinese Scholars of Shanxi Province,China(Grant No.20220001). （批准号:2022YFC3700329）
