利用磁控溅射方法在玻璃衬底上沉积一层金膜作为光学薄膜基底，在金膜上滴涂不同浓度的待测氯化钠溶液. 利 用光线与金属和溶液界面的表面等离子体的耦合，通过白光后焦面上暗环的相对位置，结合表面等离子体的相关理论，得到 不同浓度溶液的折射率，并且分析了基于后焦面成像测量液体折射率方法的误差来源，提出了提高测量精度的办法. 该实验 结合了高精度的微纳加工技术以及后焦面成像过程，提出了一种新的液体折射率测量方法，在物质分析以及传感等方面有重 要应用.

A layer of gold film is deposited on glass substrate by magnetic sputtering and different concentrations of sodium chloride solutions are drop on gold film as test samples. Refractive of sodium chloride solution is obtained by analyzing the coupling of light and surface plasmon produced on the interface of gold film and liquid，the relative position of dark ring in the back focal plane，and the theory of surface plasmon. Experimental error is calculated and the method of improving the measurement precision is proposed. This experiment combined micro and nano fabrication with the back focal plane imaging process，which has been developed a new way to measure refractive index of liquids and then has important applications in material analysis and sensor.