Design of a Probe for Sensing the Complex Index of Refraction of Liquids

摘要

In the present work we propose a new design of a compact optical sensor used to measure the complex refractive index of liquids, based on optical reflectometry near the critical angle. The present design allows easy handling and portability. It can be used to measure the refractive index of transparent liquids, optically-absorbing liquids and highly-turbid liquids, indistinctly. The range of measurement of refractive index may be, for example from 1.26 to 1.4, which corresponds to liquids based on water. The main advantage of our design is that the angle of incidence is modified through linear displacements and all optical components except one remain fixed. The refractive index measurements are obtained from the photo-reflectance and its first derivative with respect to the angle of incidence. By its characteristics, this sensor has potential for industrial applications, particularly into the food industry and within chemical and biochemical laboratories.