A sensor design that uses a grating-coupled multimode planar optical waveguide for absolute detection of the refractive indices of liquids or gases is presented. The waveguide consists of a simple 50-µm -thick, free-standing glass plate with air beneath it and the sample to be analyzed on top of it. This design offers a simple alternative to the well-known monomode waveguides, and, owing to its so-called reverse-symmetry configuration, a large detection range can be obtained.
© 2003 Optical Society of America
Nina Skivesen, Robert Horvath, and Henrik C. Pedersen, "Multimode reverse-symmetry waveguide sensor for broad-range refractometry," Opt. Lett. 28, 2473-2475 (2003)