Abstract

We report on a high-sensitivity differential refractometer based on the interaction of an evanescent wave with gaseous or liquid samples. The evanescent wave is achieved by coupling laser light into a dielectric waveguide by optical tunneling through a solid gap deposited on the base of a semi-cylindrical lens. The light reflected by this optical system carries information about the index of refraction of the sample. The technique presents sensitivity better than 10⁻⁵ for changes in the index of refraction caused by environmental conditions such as temperature, pressure and relative humidity.

© 2010 Optical Society of America