Light plays a vital role in our daily lives. It is used in compact disc (CD) players, in which a laser reflecting off a CD transforms the returning signal into music. It is used in grocery store checkout lines, where laser beams read bar codes for prices. It is used by laser printers to record images on paper. It is used in digital cameras that capture our world and allow pictures to be displayed on the Internet. It is the basis of the technology that allows computers and telephones to be connected to one another over fiber-optic cables. And light is used in medicine, to produce images used in hospitals and in lasers that perform eye surgery. The generation, transport, manipulation, detection, and use of light are at the heart of photonics. Photonics is a critical part of the future and a growing career field. In 1997 it was a $50 billion market with a projected growth of 10 to 20 percent over the next decade. Photonics technicians and engineers must master new concepts, learn new techniques, and develop new skills. To work in photonics it is necessary to have a basic understanding of the nature of light and its properties.