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The Quantum Theory of Optical Coherence

Phys. Rev. 130, 2529 – Published 15 June 1963
Roy J. Glauber


The concept of coherence which has conventionally been used in optics is found to be inadequate to the needs of recently opened areas of experiment. To provide a fuller discussion of coherence, a succession of correlation functions for the complex field strengths is defined. The nth order function expresses the correlation of values of the fields at 2n different points of space and time. Certain values of these functions are measurable by means of n-fold delayed coincidence detection of photons. A fully coherent field is defined as one whose correlation functions satisfy an infinite succession of stated conditions. Various orders of incomplete coherence are distinguished, according to the number of coherence conditions actually satisfied. It is noted that the fields historically described as coherent in optics have only first-order coherence. On the other hand, the existence, in principle, of fields coherent to all orders is shown both in quantum theory and classical theory. The methods used in these discussions apply to fields of arbitrary time dependence. It is shown, as a result, that coherence does not require monochromaticity. Coherent fields can be generated with arbitrary spectra.

DOI: http://dx.doi.org/10.1103/PhysRev.130.2529

  • Received 11 February 1963
  • Published in the issue dated June 1963

© 1963 The American Physical Society

Physics Focus

Nobel Focus: Photons at the Forefront

Published 25 October 2005

Authors & Affiliations

Roy J. Glauber

  • Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts

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