Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Historical milestones
- 3 Basics of the classical description of light
- 4 Quantum mechanical understanding of light
- 5 Light detectors
- 6 Spontaneous emission
- 7 Interference
- 8 Photon statistics
- 9 Squeezed light
- 10 Measuring distribution functions
- 11 Optical Einstein–Podolsky–Rosen experiments
- 12 Quantum cryptography
- 13 Quantum teleportation
- 14 Summarizing what we know about the photon
- 15 Appendix. Mathematical description
- References
- Index
5 - Light detectors
Published online by Cambridge University Press: 25 January 2010
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Historical milestones
- 3 Basics of the classical description of light
- 4 Quantum mechanical understanding of light
- 5 Light detectors
- 6 Spontaneous emission
- 7 Interference
- 8 Photon statistics
- 9 Squeezed light
- 10 Measuring distribution functions
- 11 Optical Einstein–Podolsky–Rosen experiments
- 12 Quantum cryptography
- 13 Quantum teleportation
- 14 Summarizing what we know about the photon
- 15 Appendix. Mathematical description
- References
- Index
Summary
Light absorption
Whereas receiving radio waves is a macroscopic process and hence belongs to the area of classical electrodynamics – in a macroscopic antenna an electric voltage is induced whereby a large number of electrons follow the electric field strength of the incident wave, in a kind of collective motion – the detection of light, so far as the elementary process is concerned, takes place in microscopic type objects such as atoms and molecules. As a consequence, the response of an optical detector is determined by the microstructure of matter. In particular, it is impossible – due to the enormously high frequency of light (in the region of 1015 Hz) – to measure the electric field strength. What is in fact detectable is the energy transfer from the radiation field to the atomic receiver, and this allows us to draw conclusions about the (instantaneous) intensity of light.
We might ask what we can say about the above-mentioned absorption process from an experimentalist's point of view. Among the basic experiences that provide an insight into the structure of the micro-cosmos is the resonance character of the interaction between light and an atomic system. The atomic system, when hit by light, behaves like a resonator with certain resonance frequencies; i.e. it becomes excited (takes up energy) only when the light frequency coincides with a value that is characteristic for the particular atom. Hence, an incident light wave with an initial broadband frequency spectrum that has passed through a gas exhibits in its spectrum dark zones, the so-called absorption lines.
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- Chapter
- Information
- Introduction to Quantum OpticsFrom Light Quanta to Quantum Teleportation, pp. 41 - 58Publisher: Cambridge University PressPrint publication year: 2004