The interference of waves evenly separated in frequency generates a periodic signal, whose intensity fluctuations depend on the phases of the individual waves. A fundamental question in telecommunications and acoustics is the minimization of the peak-to-average-power ratio (PAR): for a given spectrum, how to arrange the phases of the individual frequency components to ensure minimal intensity fluctuations of the resulting signal? For a flat spectrum a near-optimal solution is brought by the so-called Newman phases, commonly used in acoustic and radio waves. Here we transpose this property into the optical domain and prove the possibility to suppress the intensity fluctuations resulting from intermodal beating of a broadband comb of optical frequencies, whose phases are set according to a generalization of the Newman phases. We demonstrate experimentally a broadband laser, whose intensity contrast (defined as the standard deviation-to-mean ratio) is reduced down to 0.54 as compared to 1 when the phases are set randomly.