心磁测量中铯原子激光抽运磁场测量关键技术研究

项目名称： 心磁测量中铯原子激光抽运磁场测量关键技术研究

项目编号： No.10874012

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 生物科学

项目作者： 黄凯凯

作者单位： 浙江大学

项目金额： 39万元

中文摘要： 光磁共振是光抽运和射频磁共振相结合的一种双共振过程，是用光抽运来研究原子超精细结构塞曼子能级间磁共振现象的一种技术。在生物医学、激光物理、量子频标、弱磁场探测等方面都有重要应用价值。本课题运用激光抽运，射频场共振的方法，通过圆偏振光将铯原子抽运到暗态，实现偏极化。外磁场存在时，原子磁矩将以拉莫尔频率绕外磁场进动。在共振射频磁场的作用下，原子被去极化而重新吸收光子。在实验中，我们通过探测出射光光谱测得拉莫尔频率进而得到外磁场的信息,由于共振的射频信号被转化成光频信号探测，测量灵敏度提高了几个数量级。在本课题的研究过程中,我们课题组通过使用商品外腔激光器和自制的894nm外腔半导体激光器，建立了激光稳频装置,实现了低噪声磁场测量环境和高精度数字频率发生器DDS,最后实现了一种基于激光抽运射频共振的铯原子磁力仪。通过磁力仪参数优化以及铯泡缓冲气体分压强控制,我们实现的磁力仪灵敏度达到了137 fT/Hz1/2,空间分辨率小于2cm,这种磁力仪已经满足心磁测量的需要，为将来在医学中的应用研究奠定了基础,也可以用来在地磁,航空磁场,海洋磁场测量中得到应用.

中文关键词： 光磁共振;激光抽运;铯原子磁力仪;灵敏度

英文摘要： Optical detected magnetic resonance(ODMR) is a double resonance process involving optical pumping and rf magnetic resonance, which is a technique investigating the magnetic resonance among hyperfine structure Zeeman sublevels in atom. It is of great importance in biomedical , laser physics, quantum frequency standard, weak magnetic field detection and so on. We create spin polarization in the atomic vapor via the usage of a resonant circularly polarized laser beam. The magnetic moment of atoms will precess around the applied magnetic field at the Larmor frequency. The atom can be depolarized by absorption of resonant radio frequency radiation thus absorbing optical photons from the light beam again. By measuring the properties of the transmitted light the Larmor frequency can be measured, which will provide the information of the external magnetic field. The measurement sensitivity was improved several orders of magnitude by detecting the high-frequency optical signal instead of the low-frequency radio frequency signal. In our research supported by Nation Science Foundation, our group both used a commercial external cavity diode laser and a homemade 894nm laser, built the laser frequency stabilizing device, the low noise magnetic field measurement environment, the hign-precision Direct Digital Synthesizer, and realized the Cesium atomic magnetometer based on laser pumped rf magnetic resonance. By optimizing the magnetometer parameters and controlling the buffer gas pressure in Cs cell, the sensitivity of our magnetometer could reach 137 fT/Hz1/2 with a space resolution of 2cm, which satisfy the requirement of Cardio-Magnetic application. The result has made the foundation in future medical application. It may also be applied in earth magnetic, space magnetic and sea magnetic measurement.

英文关键词： optical-magnetic resonance;laser pump;Cesium magnetometer;sensitivity