ABSTRACT
Almost as important as the transmitting optical components of the previous chapter are those whose function is to reflect a major portion of the incident light. In the vast majority of cases, the sole requirement is that the specular reflectance should be as high as conveniently possible, although, as we shall see, there are specialized applications where not only should the reflectance be high, but also the absorption should be extremely low. For mirrors in optical instruments, simple metallic layers usually give adequate performance and these will be examined first. For some applications where the reflectance must be higher than can be achieved with simple metallic layers, their reflectance can be boosted by the addition of extra dielectric layers. Multilayer all-dielectric reflectors, which combine maximum reflectance with minimum absorption, and which transmit the energy that they do not reflect, are reserved for the next chapter.
