基于涡旋光束的光纤磁场传感

涡旋光束也称作光学涡旋，是指具有相位涡旋或是偏振涡旋的光束。由于在涡旋中心存在孤立的奇点，涡旋光束拥有许多独特的性质。一般把具有相位涡旋的光束称为轨道角动量光束（Orbital Angular Momentum, OAM），把具有偏振涡旋的光束称为矢量光束（Vector Beam, VB）。随着人们对涡旋本质的不断探究，涡旋光束已经在光学的多个领域得到了广泛的应用。特别在传感领域中，涡旋光束因其多自由度和存在光学奇点的特性也受到研究者的广泛关注。

磁场传感在电力系统、航空航天、生物医疗等场景有着大量的需求，由于传统基于电学的传感器存在易受电磁干扰、结构复杂、对环境要求高等缺点，人们希望利用光学磁场传感的方式解决这些问题，其中光纤磁场传感器以其体积小、灵敏度高、环境适应力强等优势受到青睐。而目前大部分光纤磁场传感器只能对标量磁场进行测量，且测量结果容易受到外界环境变化的串扰。

为此本论文主要研究了涡旋光束在磁场传感中的应用，希望利用其多自由度的优势，实现对磁场传感中的多物理量测量和矢量磁场的测量。在多物理量的测量中，本研究利用柱状矢量光束（Cylindrical Vector Beam, CVB）偏振的径向分布和磁流体在磁场下表现出的二向色性，实现了温度和磁场的同时测量。同时本研究也探究了全庞加莱光束在磁场传感中的应用，借助庞加莱球的分析手段，构建了斯托克斯相位进行磁场传感。通过分析斯托克斯相位的旋转角度测量磁场强度的变化，灵敏度为0.934°/mT 。该方法对外界干扰具有很强的鲁棒性，能避免光强波动而引起的测量误差。在此基础上，本文进一步探究了利用全庞加莱光束中奇点的移动来实现矢量磁场传感的方案，并进行了相应的仿真和实验验证。

Vortex beam, also known as an optical vortex, refers to a beam of light with phase or polarization vortex. Due to the existence of an isolated singularity at the center of the vortex, vortex beams possess many unique properties. Beams with phase vortex are generally called orbital angular momentum (OAM) beams, while beams with polarization vortex are called vector beams (VB). With continuous exploration into the nature of vortices, vortex beams have been widely applied in various fields of optics. Particularly in the field of sensing, researchers have shown great interest in vortex beams due to their multiple degrees of freedom and the existence of optical singularities.

There is a great demand for magnetic field sensing in power systems, aerospace, biomedical scenarios and so on. Traditional electric-based sensors are prone to electromagnetic interference, have complex structures, and require a high level of environmental adaptability. Therefore, researchers hope to use optical magnetic field sensing to solve these problems, with fiber-optic magnetic field sensors being favored for their small size, high sensitivity, and strong environmental adaptability. However, currently, most fiber-optic magnetic field sensors can only measure scalar magnetic fields, and their measurement results are susceptible to external environmental changes.

Therefore, this paper mainly investigates the application of vortex beams in magnetic field sensing, hoping to use their advantages of multiple degrees of freedom to achieve measurements of multiple physical quantities and vector magnetic fields in magnetic field sensing. In the measurement of multiple physical quantities, we used the radial distribution of a cylindrical vector beam (CVB) polarization and the dichroism of magnetic fluid in a magnetic field to achieve simultaneous measurements of temperature and magnetic fields. We also explored the application of the full Poincaré beam in magnetic field sensing. With the analytical tool of the Poincaré sphere, we constructed a Stokes phase for magnetic field sensing. By measuring the rotation angle of the Stokes phase, we can detect changes in the magnetic field strength with a sensitivity of 0.934°/mT. This method has strong robustness against external interference and can avoid measurement errors caused by fluctuations in light intensity. Based on this, we investigated a scheme for vector magnetic field sensing using the movement of singularities in the full Poincaré beam, and conducted corresponding simulations and experimental verifications.

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