掺Er光纤飞秒激光器中电光晶体对激光器参数的影响  

Influence of electro-optic modulator on Er-doped fiber femtosecond laser

作　　者：曹士英[1] 林百科 袁小迪 丁永今 孟飞[1] 方占军[1] Cao Shi-Ying;Lin Bai-Ke;Yuan Xiao-Di;Ding Yong-Jin;Meng Fei;Fang Zhan-Jun(Division of Time and Frequency Metrology,National Institute of Metrology,China,Beijing 100029,China)

机构地区：[1]中国计量科学研究院,时间频率计量科学研究所,北京100029

出　　处：《物理学报》2021年第7期129-139,共11页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2016YFF0200204)资助的课题.

摘　　要：由于受增益介质上能级寿命的影响,掺Er光纤光梳的梳齿线宽一般在百kHz量级.为了实现光梳梳齿线宽的压窄,一种有效的方法是在激光器中增加快速响应的电光晶体,使光纤光梳的伺服锁定带宽提高到百kHz以上,为光纤光梳的快速伺服锁定提供反馈机构.这其中,高品质的飞秒激光器是核心.基于此,本文主要研究了掺Er光纤飞秒激光器中电光晶体对激光器参数的影响.通过计算电光晶体的折射率、色散、相位延迟等参数,分析了电光晶体对激光器参数的影响,并在实验上获得了电光晶体电压对激光器重复频率和载波包络偏移频率的影响,进而通过电光晶体实现了对光纤光梳重复频率和载波包络偏移频率的锁定.通过锁定光纤飞秒激光器与窄线宽激光器的拍频信号,验证了电光晶体的引入使激光器的伺服锁定带宽提高到了236 kHz,为窄线宽飞秒光学频率梳的建立提供了技术基础.Narrow-linewidth femtosecond optical frequency comb plays an important role in the fields,such as optical clock comparison,time frequency transfer,ultrastable microwave generation,absolute distance measurement,high precision spectroscopy,etc.Due to the influence of the lifetime of the upper energy level in the gain medium,the linewidth of Er-fiber combs is generally on the order of several hundred kilohertz.In order to narrow the linewidth of comb teeth,an effective method is to insert a fast response electro-optic modulator(EOM)into the laser cavity,so that the servo bandwidth of fiber comb is extended to several hundred kilohertz,which provides a feedback mechanism for fast servo locking.Among them,a high quality femtosecond laser is the core.Based on this,the influence of the EOM on the parameters of Er-fiber femtosecond laser is studied in this paper.By calculating the refractive index,group velocity dispersion,and phase delay of the electro-optic crystal,the influence of the introduction of the EOM on the laser performance is analyzed.A LiNbO3(LN)crystal with a length of 3 mm and x-cut is selected as the EOM and inserted into the laser cavity.The influence of the applied voltage of the EOM on the repetition rate and carrier envelope offset frequency of the laser are obtained experimentally.When the voltage on the LN crystal changes from-200 to 200 V,the adjustment of repetition rate is 60 Hz and the carrier envelope offset frequency is 25 MHz.Then the two parameters are phase locked through the EOM.Furthermore,by phase locking the beat note between the fiber comb and a narrow-linewidth continue wavelength laser at 1542 nm,it is verified that the introduction of the EOM can expand the servo bandwidth of the laser to more than 236 kHz,which provides a technical basis for establishing narrow linewidth femtosecond optical frequency combs.The following work will verify the performance of comb line,that is,when the comb is locked to a narrow-linewidth laser(such as 1542 nm),the performance of comb line at waveleng

关 键 词：掺ER 光纤激光器 掺ER 光纤光学频率梳 电光晶体 伺服锁定 

分 类 号：TN248[电子电信—物理电子学]