Interference fringes from four-time correlations of wave fields

MW Hamilton
Physics, Adelaide University, Adelaide SA 5005


Abstract

Second order interference fringes in which the contrast is greatest
when the field is partially coherent, rather than fully coherent, have
been observed.  Four-time correlation functions go beyond the usual
two-time correlations that are measured in Hanbury-Brown/Twiss type
experiments.  The fringes are to be found in the Fourier transform of
such functions - these transforms are directly measured in certain
nonlinear optical experiments. However acoustics and radio offer the
possibility of measuring field directly so that fourth order
correlations of fields at four independent times can be measured.  I
justify the assertion that these are interference fringes and
describe a simple acoustic experiment in which these are measured. In
this experiment the coherence time of the field may be continuously
varied so that the maximum of contrast for finite coherence time is
clearly demonstrated.