New type liquid refractometer based on multiple total-internal reflections in heterodyne interferometry

A new type liquid refractometer based on multiple total-internal reflections in heterodyne interferometry is proposed. The sensing unit of the new-type liquid refractometer is an elongated prism, i.e., a parallelogram prism. With the new-type refractometer, we can achieve the refractive index for the tested medium only by measuring the variation in phase difference between s-and p-polarization states at the total-internal reflection effect. Its resolution can 1 × 10^-6 refractive index unit (RIU). The new-type liquid refractometer has some merits, e.g., a simple optical setup, high resolution, high sensitivity, rapid measurement, and high stability.