Field and intensity correlation in random media

We have obtained the spectral and spatial field correlation functions, C_E(Δω) and C_E(Δx), respectively, from measurement of the microwave field spectrum at a series of points along a line on the output of a random dielectric medium. C_E(Δω) and C_E(Δx) are shown to be the Fourier transforms, respectively, of the time of flight distribution, obtained from pulsed measurements, and of the specific intensity. Unlike C_E(Δω), the imaginary part of C_E(Δx) is shown to vanish as a result of the isotropy of the correlation function in the output plane. The complex square of the field correlation function gives the short-range or C₁ contribution to the intensity correlation function C. Longer-range contributions to the intensity correlation function are obtained directly by subtracting C₁ from C and are in good agreement with theory.