基于表面等离子体共振和双频激光干涉相位测量的空气折射率测量

设计了一种基于表面等离子体共振和相位检测的空气折射率实时测量系统,该系统采用双频激光外差干涉光路和具有角漂移自适应结构的表面等离子体共振传感器。理论分析表明测量光信号的p、s分量的相位差相对于参考光信号的变化与空气折射率近似呈线性关系,并由此得到测量公式,传感器的自适应结构将角漂移引起的误差降低了一个数量级并大幅提高了测量灵敏度。与Edlen公式的测量比对实验结果表明,在44.0°入射角(共振角附近)和0.1°的相位测量精度下,空气折射率的测量精度优于5×10-6。该测量系统还可为更高精度的空气折射率测量仪提供足够精确的初值。

Measurement of Air Refractive Index Based on Surface Plasmon Resonance and Phase Detection by Dual-Frequency Laser Interferometry

A measurement system of refractive index of air (RIA) based on surface plasmon resonance (SPR) and phase detection is presented. A heterodyne interference optical path is built and a SPR sensor with self-adaptive structure for angle shift is applied. Theoretical analyses indicate that the variation of the phase difference between p and s polarization components of the measurement signal versus that of the reference signal is almost linear with RIA fluctuation. Thus the formula of RIA measurement is derived. The application of the self-adaptive SPR sensor reduces the measurement error by an order of magnitude and greatly improves the sensitivity. The comparison experiments with the method of Edlen equations show that the measurement accuracy reaches less than 5×10-6 at the phase detection precision of 0.1° and the incident angle of 44.0° (which is close to the resonance angle). Furthermore, the measurement system can provide an initial estimate of RIA accurate enough for other measuring instruments with higher precision.