On the relation between coherence and monochromaticity

Jan Peřina

M. Bertolotti, Aldo Ferrari, Leonid Sereda

We discuss the relation between the coherence of light from nonstationary sources in the space–time domain and the coherence of the monochromatic components of the light. For this purpose we use Loéve’s theory of harmonizable stochastic processes, particularly the spectral representation of a nonstationary stochastic process and the relation between its correlation function and the two-frequency spectral function as a measure of coherence of the monochromatic components of the source.

Soma, Gaius

H. Rauch, H. Wölwitsch, Helmut Kaiser +2 more

The spatial coherence function in all three orthogonal directions has been measured by means of perfect crystal neutron interferometry. It has been demonstrated that the coherence function is given by the Fourier transform of the related momentum distribution, which in turn is determined by the collimation and monochromatization of the beam incident upon and traversing the interferometer. Thus, a measurement of the coherence function can replace a measurement of the momentum distribution in certain cases. Retrieval of the coherence can be accomplished by phase echo and/or postselection methods. A complete retrieval of the coherence is impossible in principle due to unavoidable loss factors.

Martti Hanhisalo, M. S. Mirmoosa, Tero Setälä +2 more

Light is known to exhibit quantum uncertainty in terms of its amplitude, phase, and polarization. However, quantum uncertainty related to coherence, which is also a fundamental physical property of light, remains to be considered. Here, we formulate and explore the concept of quantum optical coherence uncertainty. We focus on the first-order coherence of the simplest possible light field, a purely monochromatic plane wave, which is classically completely stable. Starting from a scalar treatment, we show that the field displays zero coherence uncertainty only for a number state. We then proceed to the vectorial regime and establish that any state leads to coherence fluctuations, governed by a set of uncertainty relations depending on the polarization state and space-time points. Our work thus provides fundamental insights into the quantum character of optical coherence, with potential benefits in applications using highly sensitive interferometric and polarimetric techniques.

Ingolf Volker Hertel, Claus-Peter Schulz