Introduction

We saw in paragraph B.2 that the spectral content of the interfering waves influences the signal, especially the modulation term. In the case of two waves that are perfectly monochromatic and have the same wavelength, the fringes have the maximum contrast. This paragraph aims to study the influence of the wave spectral width on the fringe contrast. The influence of the spectral width describes the temporal coherence of light. The description of the source's spectral content is based on the notion of spectral energy density. This notion will be explained in the following.