Fabry-Perot cavity enhanced prism for highly sensitive refractive index measurement of water

An instrument for measuring the temperature of distilled water is proposed, theoretically analyzed and experimentally demonstrated. The instrument is composed of a Fabry-Perot cavity, a V-block prism, and a photodiode as the receiver. The detection limit of the instrument as high as 4.8 × 10−8 RIU has been demonstrated, which is one order of magnitude higher than that of the state-of-the-art V-block refractometers, without increasing the instrument size.