Optical Modeling of MEMS

The theory and modeling of optical MEMS structures are discussed in this chapter. Optics is related to the processing of silicon MEMS in many ways. A typical example of optical MEMS (or micro-optical-electromechanical systems, MOEMS) is a movable mirror on silicon. This chapter discusses the most relevant optical properties of silicon and the ways to manipulate them. Often the simplest way to change n is heating. In addition to silicon, many other materials are used in optical MEMS. There is an assumption that the absorption of the propagation medium is negligible, unless otherwise stated. The simplest model for representing light propagation is called geometrical optics. Matrix optics is based on the use of paraxial approximation in ray optics. It is commonly used in the design of optical systems, especially in free space optics. With geometrical optics it is difficult to accurately explain and model such phenomena as interference and diffraction, or to predict the exact amount of light reflected from a material interface. Many optical simulation tasks in MEMS can be carried out by considering light as a simple scalar field. The design of optical MEMS mainly relies on numerical modeling methods. The ray tracing method is often the simplest and most effective simulation tool. Thin film stacks are 1D structures that have several applications in optical MEMS. In many applications light propagates with large angular variations or through complicated optical structures with large and continuously changing refractive index variations. Gratings are utilized in many optical applications.