Sensors that are used to detect optical radiation are usually confined to use in two types of detectors: thermal detectors and photon detectors. Thermal detectors sense the heat generated by the absorbed radiation, so their operation is a two-step process: conversion of the radiation energy into heat, followed by conversion of the heat energy into the energy of an electrical signal. The incident radiation is absorbed to change the material temperature, and the resultant change in some physical property is used to generate an electrical output.
Despite this two-step operation, thermal detectors are relatively simple devices (see Fig. 1.1) that operate primarily at ambient temperature. In general, a thermal detector is suspended on lags that are connected to a heat sink. The signal does not depend upon the photonic nature of the incident radiation.
Online access to SPIE eBooks is limited to subscribing institutions.