Most optics experiments do not take place in vacuum, and the effect of the medium on the propagation of an electromagnetic wave is of fundamental importance in designing an optical component. The behavior of optical components is strongly defined by the materials from which they are made, and whereas the shape of the interface or interfaces is also of primary importance, material characteristics play an equally important role in defining what happens to a light wave impinging on an optical structure.

We begin this section by discussing the means by which we characterize materials optically. A key concept here is the refractive index, the wavelength-dependent, complex, frequently direction-dependent and occasionally nonlinear parameter that defines most of the important propagation conditions for an optical field. We will discuss its physical origins and implications for wave propagation, and also address absorption and scattering. In the second half of the chapter we will provide an overview of the most relevant materials used in micro-optics: for each of these we will learn about their most important characteristics, and also consider their relative advantages and disadvantages when compared with alternative material systems.

Material choices

As we will see in detail below, most micro-optical components are fabricated using one or more of five basic material systems: glass, semiconductors, dielectrics, plastics, and specialized crystals.