Intensity correlation function, homodyne

In an actual QELS experiment performed by using the homodyne regime, the time correlation function of the intensity of the scattered light is measured. Because of the Gaussian nature of the electric field, the time correlation function is given by the square of the correlation function of the electric field see equation 14). The equation is... 

When monochromatic light is scattered by moving particles that show thermal motion, the field amplitudes E oo) show a Gaussian distribution. The experimental arrangement for measuring the homodyne spectrum is shown in Fig. 7.31. The power spectrum P (jo) of the photocurrent (7.68), which is related to the spectral distribution I oo), is measured either directly by an electronic spectrum analyzer, or with a correlator, which determines the Fourier transform of the autocorrelation function C(r) a i t)) i t -f- r)). According to (7.63), C(r) is related to the intensity correlation function G (r), which yields (7.64), and I co). 

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