表面等离子共振现象的新应用——微弱磁场的测量

提出了一种新的表面等离子体共振传感器, 它包含三层结构: 棱镜、金属薄膜及二能级介质. 通过理论分析发现, 与通常表面等离子体共振系统不同, 这一物理系统中同时存在两种共振效应 (表面等离子体共振和能级间量子跃迁的共振效应), 它们共同作用的结果导致一系列新的物理现象, 其中一个令人感兴趣的现象是入射光的反射率对外场导致的微小能级移动十分敏感 (这一现象是通常的表面等离子体共振系统所不具有的). 由于能级移动依赖于外场, 所以最终入射光的反射率对外场具有灵敏的响应. 本文以外磁场导致能级移动的情况进行了理论计算, 结果表明, 这种表面等离子体共振系统的入射光的反射率对外加磁场极其敏感. 这一特性可以用来测量物质表面附近的微弱磁场, 有可能发展成为一种新型检测技术.

New application of surface plasmon resonance-measurement of weak magnetic field

In this paper, we present a new kind of surface plasma resonance (SPR) sensor. It comprises three layers, an upper coupling prism, a middle metal layer, and a bottom semi-infinite two-level atom medium. Based on theoretical analysis on this SPR system, it is found that there are some new phenomena due to the coexistence of two resonant effects, i.e., the surface plasmon resonance and the resonant quantum transition between atomic energy levels. An interesting phenomenon is that the reflectivity of the incident light is very sensitive to the shift of atomic level induced by external field. This phenomenon is absent in ordinary SPR systems. Because the shift of atomic level is determined by external field, ultimately, the reflectivity of the incident light is sensitive to the external field. In this paper calculations are presented in the case where the external field is a magnetic field. It is found that the reflectivity of the incident light is very sensitive to the magnetic field. This property can be used for measuring a very weak magnetic field near surface of matter , thus it can be used for developing a new detection technology.