Interference: dark rays description

Abstract

The concept of spatial coherence wavelet has been introduced some years ago with very productive results. It has given new insight on the fundamental optical phenomena, and has predicted novel light characteristics like polarizations domain and transverse energy transference. The concept of marginal power spectrum emerges as the amplitude of the wavelet and provides a phase-space representation of the optical field in any state of spatial coherence. Its values have energy units and are carried by the spatial coherence wavelets along specific paths or rays. Some of them, called carrier rays, are corresponding to the radiant energy of the field, but the rest, called dark (or tamasic) rays, do not contribute to the radiant energy, i.e. they take on positive and negative values, symmetrically distributed, which are responsible for the constructive and destructive interference after redistributing the radiant energy of the field. This description of interference is illustrated by analyzing the Young experiment, gratings and one-dimensional apertures. Furthermore, the principle of spatial coherence modulation is introduced, showing its feasibility for practical applications in beam shaping.