Passive optical systems

Abstract

Introduction Practical photonic systems can conveniently be divided into four distinct parts: (a) the optical source (or sources), (b) a passive optical structure, (c) an active optical structure, and (d) a detection system. A good example of such a system is the human eye, which is shown schematically in Fig. 13.1. In this system the source of light is the Sun, or artificial lighting that renders objects visible to the eye. The passive optical structure includes the cornea, the intraocular fluid, and other fixed structures in the eye. The active optical structure includes the deformable eye lens, whose shape is controlled by the ciliary muscles, and the iris, whose diameter is adjusted to control the amount of light entering the eye. The detector in this system is the retina, where photons are absorbed by special molecules, leading to chemical reactions that produce charges and subsequent electrical signals to the brain along the optic nerve. We have already explored in some detail the fundamental physics, constructional details, and properties of lasers.We have also seen the connection between the amplifying medium and the optical structures that turn the laser amplifier into an oscillator. In this and the following chapters we will further examine the characteristics of various passive and active optical structures that are important in photonic systems. Initially we will discuss the characteristics of important passive optical components and systems. These will include optical materials, lenses, mirrors, prisms, diffraction gratings, interferometers, crystals, polarizers, and optical fibers.