Coherence in Classical Electromagnetism and Quantum Optics

Abstract

This thesis is a study of coherence theory in light in classical electromagnetism and quantum optics. %The coherence is quantified Specifically two quantities are studied: The degree of first-order temporal coherence, which quantifies the field-field coherence, and the degree of second-order coherence, quantifying the intensity-intensity coherence. In the first part of the thesis these concepts are applied to classical electric fields; to both the ideal plane wave and to chaotic light. We then study how they can be measured using two interferometer technologies from optical astronomy, specifically with the Michelson stellar interferometer and the intensity interferometer.

In the second part we define the quantum degrees of first- and second-order coherence. These are calculated for light in a quantum coherent state, in a Fock state and for light in a mixed thermal state. The results for the coherent state and the thermal state are found to be analogous to those obtained for the ideal plane wave and chaotic light, respectively, from the classical coherence theory seen in the first part.

We proceed to investigate the properties of the three-level laser with the aim of showing that far above threshold it develops similar photon statistics and values for the degrees of first- and second-order coherence, to light in a coherent state. The mechanism of phase-drift in the laser is also looked into. Subsequently the Mølmer-model is discussed, where it is demonstrated that the coherent state is not a necessary construct, but merely a convenient one, in describing phenomena in quantum optics.