Reflective type liquid refractometer based on multiple total internal reflections and attenuated total reflections in heterodyne interferometry

In this paper, a reflective type liquid refractometer based on multiple attenuated total reflections and total internal reflections in heterodyne interferometry is proposed. The liquid refractometer is designed as a reflective elongated prism that is made of BK7 glass. The shorter-side surface of the reflective elongated prism was coated with 2 nm Ti-film and 45.5 nm Au-film, but the longer-side surface of that was not coated with metal films. With the new type liquid refractometer, the refractive index for the tested medium can be obtained only by measuring the phase difference between the p-and s-polarization lights due to the multiple attenuated total reflections and total internal reflections effects. Its resolution can reach 1´ 10^-6 refractive index unit (RIU). The reflective type liquid refractometer has some merits, e.g., high resolution, high sensitivity, stability, and in real-time test, etc.