Measurement of Potassium Vapor Number Density Based on Surface Plasmon Resonance

碱金属气室是用于磁场测量的原子磁强计的主要组成部分。为了实现对气室中碱金属气体数密度的测量，本文提出了一种新的基于表面等离子体共振效应的碱金属气室密度测量方法。碱金属原子在极化状态下不同数密度的碱金属气体会有微小的折射率差异，通过表面等离子体共振(SPR)的方法测量该差异，实现对该其数密度的测量。研究分析了适合钾原子气室数密度测量的角度调制的Kretschmann型棱镜耦合式SPR结构。理论计算结果表明，在共振角度42.6˚到46˚内，对应的钾金属数密度从1.97 × 1012 cm−3到2.01 × 1016 cm−3，覆盖大部分较为常见的钾原子气室的密度范围。本文提供了一种新型实时、无接触、空间分布式定点的测量碱金属气体密度方法，对原子磁强计的发展具有重要意义。The alkali metal gas chamber is the main component of the atomic magnetometer used for magnetic field measurement. In order to measure the number density of alkali metal gas in the gas chamber, a new method based on surface plasmon resonance effect is proposed. Alkali metal atoms in the polarization state of different number density of alkali metal gas will have a small refractive index difference, through the surface plasmon resonance (SPR) method to measure the difference, to achieve the measurement of the number density. An angle-modulated Kretschmann prism-coupled SPR structure suitable for potassium atom chamber number density measurement is studied and analyzed. The theoretical calculation results show that the corresponding potassium metal number density ranges from 1.97 × 1012 cm−3 to 2.01 × 1016 cm−3 at the resonance Angle of 42.6˚ to 46˚, covering most of the density range of the more common potassium atom gas chamber. This paper presents a new real-time, contactless, spatially distributed fixed-point measurement method for alkali metal gas density, which is of great significance to the development of atomic magnetometer.