Power spectral density of self-mixing signals from a flowing Brownian motion system

An analytical expression for the power spectral density of the self-mixing signals from a flowing Brownian motion system irradiated by a focused Gaussian field is derived from the time autocorrelation function of the signals. The power spectral density is composed of two Voigt functions. An improved series summation method (SSM) is proposed to calculate the Voigt function. The characteristics of the power spectral density are analyzed according to the numerical results. The power spectral density can hopefully be used for measuring the flow velocity and the particle size.