用于光学俘获的光电反馈式激光强度噪声抑制  

Suppression of Laser Intensity Noise via Optoelectronic Feedback for Optical Trappings

作　　者：张佳羽 常昊博 田壮壮 吕鑫[1] 李刚[1] 张鹏飞[1] 张天才[1] ZHANG Jia-yu;CHANG Hao-bo;TIAN Zhuang-zhuang;LÜXin;LI Gang;ZHANG Peng-fei;ZHANG Tian-cai(State Key Laboratory of Quantum Optics and Quantum Optics Devices,Institute of Opto-Electronics,Shanxi University Taiyuan 030006,China)

机构地区：[1]量子光学与光量子器件国家重点实验室山西大学光电研究所,山西太原030006

出　　处：《量子光学学报》2023年第4期82-88,共7页Journal of Quantum Optics

基　　金：国家自然科学基金(U21A6006,U21A20433,11974223,119724225,12104227,12104278);山西省“1331工程”提质增效建设计划项目(2022-07-01)。

摘　　要：在光学俘获和操控单原子的实验中,激光的低频强度噪声通常会加热原子,从而缩短其存储时间并破坏其内态相干性。我们采用了一种基于电光振幅调制器(EOAM)的单级反馈环路来抑制激光低频噪声,实现了0~1 MHz的强度噪声的有效抑制,100 kHz以下的噪声可降低20 dB,500 kHz以下的噪声可降低10dB。噪声抑制的频率范围涵盖了光学偶极阱的典型参量加热频率。将该装置用于单个铯原子实验将单个原子在偶极阱中的存储时间延长两个数量级,测量的退相干时间也增加了5倍。In the application of vacuum optical tweezers,a dipole trap formed by laser light with a spatial gradient is usually used to trap neutral atoms or micro/nano particles.In the experiment of optical trapping neutral atoms,dipole trap with laser frequency far detuned from the atomic transition is usually adopted in order to suppress the photon scattering rate from the trapped atom.The storage time of the optically trapped atoms is mainly affected by the intensity noise and the pointing noise associated with the dipole field.The storage time is far less than the value determined by the background vapor pressure.In order to prolong the storage time as well as the decoherence time of the trapped particles,we invent a method to use a single-stage feedback loop based on an electro-optical amplitude modulator(EOAM)to suppress the low-frequency intensity noise associated with a 1064 nm laser beam.The intensity noise from 0 Hz to 1 MHz can be effectively suppressed with a reduction up to 20 dB below 100 kHz and 10 dB below 500 kHz.The standard deviation of optical power fluctuation has decreased to 0.5%,which is an order of magnitude improvement.The noise-suppressing range covers the typical parametric heating frequencies of the optical dipole trap.Therefore,it can be used to improve the trapping performance of these particles,such as the storage time of particles and the coherence time of quantum states.By applying the setup to our single cesium atom experiment,the atomic heating rate is reduced by two orders of magnitude.Thus,we can extend the storage time of a single atom by two orders of magnitude.The measured decoherence time is also enhanced five times.The setup is simple and flexible,so it can be easily applied to the optical trapping of a neutral atom or nano/micron particles with a laser with all kinds of wavelengths.

关 键 词：光电反馈 强度噪声 光学俘获 原子存储时间 原子退相干时间 

分 类 号：O439[机械工程—光学工程]