ABSTRACT
Not having to retain knowledge of the photon phase means incoherent, broadband continuum detectors are not subject to the quantum mechanical noise limit of coherent receivers (Shimoda et al., 1957; Zmuidzinas, 2002). A simplified block diagram of an incoherent detector system is shown in Figure 7.1. Light from the telescope enters a cryostat where it encounters a filter and/or dispersive optical system that selects the range of frequencies to be observed (Stacey, 2011). The filtered light is then conveyed to one or more detectors that
PROLOGUE
The first detector used for THz astronomy was a bolometer. Bolometers belong to the incoherent family of detectors. Such detectors are extremely sensitive to the power of an incident signal, but do not “phase-tag” the incoming photons as is done by coherent receivers. Incoherent detectors are well suited for conducting broadband observations of dust in the ISM (interstellar medium), and for performing low resolution spectroscopy of the Milky Way and external galaxies. In this chapter, three types of incoherent detectors will be introduced: the semiconductor bolometer, the superconducting transition edge sensor, and the microwave kinetic inductance detector.
