面向Li原子D1线频率测量应用的掺铒飞秒光纤光梳系统

Er:fiber Femtosecond Optical Frequency Comb Aimed at Measurement of Frequency of D1 Line in Li Atoms

报道了自主研制的面向Li原子D1线频率测量应用的掺铒飞秒光纤光学频率梳,包括飞秒激光源,频率探测及控制单元,光谱展宽及拍频单元.光纤光梳系统中飞秒激光光源是一套基于非线性偏振旋转锁模机制的掺铒飞秒光纤激光器,重复频率为196.5MHz,中心波长为1 572nm.利用f-2f法探测载波包络相移频率,获得信噪比约为40dB的信号(分辨率带宽300kHz).改变飞秒激光光源泵浦控制载波包络相移频率、频率稳定度是3.74×10-18/τ1/2;通过电光晶体和压电陶瓷改变飞秒激光光源腔长来控制重复频率frep、频率稳定度是1.75×10-13/τ1/2.利用高非线性光纤和倍频晶体将光纤光梳直接输出光谱由1 520～1 607nm扩展到671nm,获得了单模功率为208nW的光信号.与671nm单频激光拍频产生约为60dB(分辨率带宽1Hz)信号,满足Li原子D1线频率测量实验的需求.

A home-made Er:fiber optical frequency comb aimed at measurement of frequency of D1line in Li atoms was demonstrated.The system includes Femtosecond laser,f rep and f ceo detection and control,Spectral broaden and Beat unit.Femtosecond laser is a home-made nonlinear-polarization-rotation mode-locked laser,oscillating at around1572nm with a repetition rate of196.5MHz.The f ceo detection is accomplished by using the f-2f beating method,the signal-to-noise ratio of f ceo about40dB with300kHz.f ceo controlled by changing the pump current and its in-loop frequency instability,evaluated by the Allan deviation,is approximately3.74×10^-18/τ^1/2;f rep controlled by changing the cavity length of femtosecond laser,its in-loop frequency instability is approximately1.75×10^-13/τ^1/2.Optical spectrum is broadened and multipliered from infrared1520-1607nm to671nm by using highly nonlinear fiber and MgO:Periodically poled lithium niobate.Finally,obtaining the beat signal between sigle-frequency laser and optical comb about60dB with1Hz.