The influence of nonparaxiality on the spectral behavior in Young's experiment illuminated by partially coherent light

Starting from the Rayleigh–Sommerfeld diffraction integral, this paper studies the spectral behavior in Young's experiment illuminated by nonparaxial partially coherent light and compares with the paraxial case, where the influence of nonparaxiality of partially coherent light on the spectral shifts and spectral switches is stressed. It is shown that there is a spectral shift in the nonparaxial case relative to the paraxial one and the critical position changes, at which the spectral switch occurs. The ratio of the waist width to the central wavelength w0/λ0 and relative spatial correlation length Δ affect the spectral difference. The smaller w0/λ0 is, the larger the difference between the nonparaxial and paraxial results appears. The effect of relative spatial correlation length Δ is relatively small. (classical areas of phenomenology)