Basic Tranducers for Radiation

Abstract

The term photodetectors is usually applied to transducers for a very narrow range — the visible and near infra-red — of the electromagnetic spectrum. There is of course no real limit to the electromagnetic spectrum; it stretches from very low frequency waves of less than 1 Hz, observed by magnetometers, to X-rays and γ-rays of frequencies up to 10²⁰ Hz, as indicated in figure 7.1. However, we will confine our attention here to photodetectors, since this range is particularly important in many types of measurement.