摘要
利用超稳腔PDH(Pound-Drever-Hall)稳频技术,对自研的分布Bragg反射(DBR)单纵模光纤激光器稳频,获得亚赫兹线宽超稳激光的稳频结果。通过优化腔结构参数,辅以绝热封装和精密温控等措施,并在腔内设置可快速宽范围调谐激光频率的压电陶瓷(PZT),研制出了可满足超稳腔PDH稳频要求的自由运转DBR光纤激光器。基于腔长为10 cm、精细度为360000的超稳光腔频率为参考频率,PDH稳频后光纤激光器的1 s和100 s频率不稳定度分别达到了6×10^(-16)和8×10^(-15),频率噪声降低至8×10^(-3)Hz2/Hz@1~10 Hz,激光线宽窄至280 mHz,由此表明研制的光纤激光器可用于构建亚赫兹线宽超稳激光光源。
Objective Ultrastable low-noise ultranarrow linewidth laser light source has a wide range of applications in precision measurement,optical atomic clock,time-frequency transmission,and low-noise microwave generation.Ultrastable cavity Pound-Drever-Hall(PDH)frequency stabilization technology is one of the most important solutions for obtaining such ultrastable lasers.Based on this,the linewidth of the distributed feedback(DFB)single-frequency fiber laser has reached the order of millihertz.In addition to the performances of the ultrastable cavity and servo system,the available linewidth and frequency instability of the ultrastable fiber laser depend on the performances of the linewidth,frequency drift and noise level of the free-running fiber laser,and the laser frequency-tuning mechanism.Although many research institutions in China have developed single-longitudinal-mode fiber lasers with frequency-tuning mechanisms and the laser frequency has been stabilized within a hundred kilohertz for a long time by the saturated-absorption frequency stabilization technology based on fine transition spectral lines of gas molecules,home-made single-frequency fiber laser has not been applied to ultrastable cavity PDH frequency stabilization technology to obtain subhertz-linewidth ultrastable fiber laser source.Therefore,it is very necessary to investigate the PDH frequency stabilization with such home-made single-frequency fiber lasers.Methods By optimizing the structure parameters of the laser cavity,adopting adiabatic packaging and precision temperature control,and integrating the piezoelectric transducer(PZT)in the cavity that can quickly and widely tune the laser frequency,a free-running DBR fiber laser that can be used to obtain an ultrastable laser via ultrastableoptical-cavity PDH frequency stabilization was developed.The laser power was boosted by a low-noise single-mode polarization-maintaining fiber amplifier.The ultrastable optical cavity used for frequency stabilization was made of ultralow expansion(ULE)glass with a cavity length of 10 cm.The corresponding free spectral range(FSR)was1.5 GHz and the fineness was 360000.The fiber laser was modulated by an electro-optical modulator(EOM)and then coupled into the optical cavity.The laser with modulated sidebands reflected by the optical cavity was detected with a photodetector and then mixed with the drive signal of the EOM through a mixer to obtain the error signal for laser frequency stabilization.The error signal was processed by the servo system,and the low-frequency component was fed back to control the voltage of the PZT to compensate the low-frequency fluctuations of the laser frequency.The high-frequency component was fed back to the acousto-optic modulator(AOM)drive controller to achieve the highfrequency fluctuation compensation of the laser frequency.To evaluate the effect of PDH frequency stabilization of our fiber laser,two DBR fiber lasers were stabilized to the two adjacent cavity modes of the optical cavity at the same time.The performance parameters of the frequency stabilization fiber laser were then measured by the beat frequency of the two frequency-stabilized lasers.Results and Discussions The developed DBR fiber laser exhibits stable single-longitudinal-mode oscillation characteristics[Fig.2(a)].The relationship between the amount of change in the output laser frequency and the modulation frequency of the tuning voltage when the PZT is applied with different voltage values is given[Fig.2(b)].The tuning bandwidth of the laser frequency adjusted by PZT is about 8--10 kHz and the maximum tuning range exceeds 3.2 GHz.The signal-to-noise ratio of the output laser is about 60 dB[Fig.3(a)]and the 3-dB linewidth of the laser is about 1.25 kHz[Fig.3(b)].The error signal is recorded by the oscilloscope when a triangular-wave sweep voltage of 7 Vat 20 Hz is applied to PZT[Fig.5(a)].The error signal then changes to a straight line after the laser frequency is locked to the reference cavity[Fig.5(b)].There is a drift in the frequency of the beat frequency signal.The range of drift within 1 his less than±20 Hz[Fig.6(a)]and the frequency drift of each laser after frequency stabilization is less than±10 Hz.The frequency instability of the frequency-stabilized fiber laser corresponding to 1 sand 100 sis 6×10^(-16) and 8×10^(-15),respectively[Fig.6(b)].Fig.7(a)displays the measured frequency noise power spectrum of the frequency-stabilized fiber laser in the range of 1 mHz--100 kHz.The frequency noise is reduced by more than eight orders in the range of 1 mHz--10 Hz.The frequency noise is reduced to about 8×10^(-3) Hz^(2)/Hz especially from 1 to 10 Hz.Using the measured beat frequency data,the laser linewidth after Lorentz fitting is 280 mHz[Fig.7(b)].Conclusions We have demonstrated the results of ultrastable cavity PDH frequency stabilization based on a homemade single-frequency DBR fiber laser at 1550 nm.By optimizing the structure parameters of the laser cavity,adopting adiabatic packaging and precision temperature control,and integrating the PZT in the cavity that can quickly and widely tune the laser frequency,a free-running DBR fiber laser that can be used to obtain an ultrastable laser via ultrastable-optical-cavity PDH frequency stabilization is developed.Using an ultrastable optical cavity with a length of 10 cm and a fineness of 360000,the frequency drift of the fiber laser after PDH frequency stabilization is less than±10 Hz and the frequency instability at 1 sand 100 sis 6×10-16 and 8×10-15,respectively.The frequency noise is reduced to 8×10^(-3) Hz^(2)/Hz at 1--10 Hz and the linewidth is narrowed down to 280 mHz.It is shown that the main performances of our lasers can be used to construct subhertz-linewidth ultrastable laser light sources,which can be used in fields such as gravitational wave detection,precision measurement,and time-frequency transmission.
作者
姚波
陈群峰
陈雨君
吴斌
张骥
刘昊炜
魏珊珊
毛庆和
Yao Bo;Chen Qunfeng;Chen Yujun;Wu Bin;Zhang Ji;Liu Haowei;Wei Shanshan;Mao Qinghe(Anhui Provincial Key Laboratory of Photonics Devices and Materials,Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei,Anhui 230031,China;Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan Hubei 430071,China;School of Environmental Science and Optoelectronic Technology,University of Science and Technology of China,Hefei,Anhui 230026,China;The 41st Research Institute of CETC,Qingdao,Shandong 266555,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2021年第5期192-200,共9页
Chinese Journal of Lasers
基金
国家重点研发计划(2017YFB0405100,2017YFB0405200)
中国科学院战略性先导科技专项(B类)(XDB21010300)
国家自然科学基金(61805258,61377044)
安徽省科技重大专项(201903a07020021)
先进激光技术安徽省实验室主任基金(20191001)。
