ABSTRACT
This chapter considers the influence of noise – any fluctuating unwanted output – on the sensitivity of the detection system. It begins with an ideal photon detector and aims to derive an expression for the best achievable sensitivity, limited only by the properties of the incident radiation. The chapter looks at ways of characterising and minimising their effects on the overall sensitivity of the measurement. The sensitivity of a detector, or detector system, is often expressed in terms of the noise equivalent power. The detector and other components will contribute a negligible amount of additional noise compared to the photon noise. The random fluctuations in the photon arrival rate are called photon shot noise. Generation-recombination noise occurs in semiconductors and is due to the random thermal generation and recombination of electron/hole pairs giving rise to fluctuations in carrier concentration and so leading to a noise current if there is an applied voltage.
