Diffraction in Dispersive Media: A System-theoretical Approach

After a short reminder of system theory, it is shown that polychromatic diffraction in dilute dielectric dispersive media leads to an input-output relationship between field amplitudes incident on and emerging from a spatially modulating transparency. If Rayleigh-Sommerfeld diffraction theory is used and in Green's function the vacuum wavenumber is replaced by a function of susceptibility, which depends on frequency, then the system-theoretical interpretation of the formula is straightforward. Linearity, time-invariance and causality are satisfied and the state space is physically identifiable.