基于增强条纹去除的超冷原子成像  

Ultracold atomic imaging based on enhanced fringe removal method

作　　者：王帅 李希[1,2,3] 姚星灿 Wang Shuai;Li Xi;Yao Xing-Can(Hefei National Research Center for Physical Sciences at the Microscale,School of Physical Sciences,University of Science and Technology of China,Hefei 230026,China;Shanghai Research Center for Quantum Sciences,CAS Center for Excellence in Quantum Information and Quantum Physics,University of Science and Technology of China,Shanghai 201315,China;Hefei National Laboratory,University of Science and Technology of China,Hefei 230088,China)

机构地区：[1]中国科学技术大学物理学院,合肥微尺度物质科学国家研究中心,合肥230026 [2]中国科学技术大学,中国科学院量子信息与量子科技创新研究院,上海量子科学研究中心,上海201315 [3]中国科学技术大学,合肥国家实验室,合肥230088

出　　处：《物理学报》2024年第14期193-200,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11874340);国家重点研发计划(批准号:2018YFA0306501)资助的课题.

摘　　要：吸收成像是超冷原子实验中定量测量的基础.典型的成像过程涉及记录探测光场和原子吸收光场的照片.在拍摄这两张照片的时间间隔内,由于探测光不可避免的抖动,会在成像过程中引入条纹噪声模式.常规的条纹去除算法虽然可以抑制这种噪声,但由于其忽略了原子吸收效应对噪声信号的调制,使得原子团上会出现无法完全消除的剩余条纹,并且这一现象会随着原子密度的增大而愈发明显.本文提出了一种创新的增强条纹去除算法,该方法考虑了原子的吸收效应,并通过主动调制噪声信号的强度,从根本上避免了剩余条纹的产生并显著提高了成像的信噪比.在处理均匀费米气体的吸收成像时,新算法成功将表征原子密度波动的相对标准偏差降低约37%.此外,本文还利用该方法对6Li费米原子超流中的第二声波进行了定量观测.与传统的条纹去除算法相比,我们的新方法将密度波关联函数的对比度提高了近4倍,密度响应谱强度提升约15%.上述结果表明,增强条纹去除算法不仅可以有效地抑制条纹噪声,而且更有利于在高密度原子体系中识别和探测一些重要物理效应.Absorption imaging is the foundation for quantitative measurements in experiments on ultracold atoms.This technique mainly involves capturing images of both the probing light field and the atom absorption light field.In this process,the unavoidable jitter of the probing light introduces imaging noise of fringe patterns into the atomic optical density distribution OD.In conventional fringe removal algorithms,this type of noise can be normalized by constructing an optimal reference image from multiple reference images that have been actually taken,which shares similar fringe patterns to an absorption image(Fig.(a)).Although this method works well in the region without atomic signal,they often overlook the modulation of the noise signal due to atomic absorption effects,leading to persistent residual fringes on the atom clouds.This problem becomes more pronounced with atomic density increasing.Here,we propose an enhanced fringe removal algorithm that takes into account the effects of atomic absorption,and actively modulates the intensity of the noise signal in the reference image constructed by conventional fringe removal algorithms(Fig.(b)),effectively preventing the residual fringes from forming,thus significantly improving the signal-to-noise ratio of the atomic images.When applied to the absorption imaging of homogeneous Fermi gases with high density,as shown in Fig.(d),this new algorithm successfully reduces the relative standard deviation of optical depth characterizing atomic density fluctuations by approximately 37%,which is about 3 times the relative standard deviation by conventional algorithm.Three subgraphs in Fig.(e)show the optical depth distribution at corresponding data points labeled by square boxes in Fig.(d).Furthermore,we also use this technique to quantitatively determine the second sound in the unitary Fermi superfluid of 6Li atoms.Compared with conventional fringe removal methods,our new algorithm increases the correlation function’s contrast of the density wave nearly 4 times,therefore enhan

关 键 词：条纹去除 吸收成像 幺正费米超流 第二声波 

分 类 号：O562[理学—原子与分子物理]