Optical Sensing Apparatus And Method

Optical devices and techniques are disclosed for sensing properties of an environment with improved stability and lower cost. In a disclosed embodiment, there is provided a substrate having an index of refraction ns. A waveguide layer is provided and has a surface adjacent the substrate, the waveguide layer having an index of refraction nf that is greater than ns. A superstrate is provided adjacent the opposing surface of the waveguide layer, the superstrate having an index of refraction nc that is less than nf, the index of refraction of the superstrate being affected by the environment. An optical beam is injected into the waveguide layer such that at least two modes of the beam propagate in the waveguide layer. The interfering product of said at least two modes of the beam which have propagated through the waveguide layer is then detected.Georgia Tech Research Corporatio