Slab Waveguides in Chemistry

Abstract

Technological development in the telecommunications and related areas have made available a wide variety of optical structures such as thin silica rods, hollow cylinders, fiber bundles, and many planar geometries such as thin films or channels resting on flat substrates. These devices have become the basis of various chemical sensor studies. The application of cylindrical fiber optics has been leveraged heavily in developing microscopic detectors in which they serve as light pipes to transport spectrometric information between the source, analyte, and photodetector. Slab waveguides, on the other hand, offer many advantages over their cylindrical counterparts. Slab waveguides consist of planar or rectangular structures with a thickness ranging from 0.1 μm to 1 mm. They can also be molded as multilayers or channels on a substrate. Both thin and thick slab waveguides are useful in chemical sensing. In this article, the concept of waveguiding phenomena in thick and thin waveguides is introduced. Emphasis is placed on both the quantum nature and a phenomenological description of light guiding in thin slab waveguides. Several optical coupling techniques are discussed. The remainder of the article is devoted to specific applications in chemistry.