OPTICAL AND INFRARED DETECTORS FOR ASTRONOMY Basic principles to state-of-the-art

Detectors play a key role in an astronomical observatory. In astronomy, the role of the telescope and instrument is to bring light to a focus in effect, the telescope-instrument act as “spectacles”. The detectors, meanwhile, have the critical role of sensing the light the detectors are the “eyes” of an observatory. The performance of an astronomical observatory is directly dependent upon the performance of its detector systems. In many ways, today’s optical and infrared detectors are nearly perfect, with high quantum efficiency, low readout noise, high dynamic range and large arrays of pixels. However, as good as the detectors are, there are limitations that must be understood and respected in order to produce the best astronomical instruments and thereby, the best science. This chapter explains how optical and infrared detectors work, from basic principles to the state-of-the-art. The role of optical and infrared detectors in an observatory is presented, and the state-of-the-art is related to an ideal detector. An overview of the detector physics is presented, showing that the detection of light is a 5 step process. Each step in this process is explained in detail in the subsequent sections. The chapter concludes with references for further information.