The invention relates to a method for the synthesis of electromagnetic radiation, wherein electromagnetic radiation having a spectrum comprising two or more spectral components is generated and phase setting of the electromagnetic radiation is performed. The invention proposes that the phase setting comprises phase shifting of the spectral components of the electromagnetic radiation, wherein the relative phase relationship of the spectral components is predeterminable. In addition, the invention relates to an apparatus for the synthesis of electromagnetic radiation, said apparatus comprising a pulsed laser (1), which generates a sequence of temporally equidistant light pulses, wherein the spectrum of the electromagnetic radiation of the pulsed laser (1) is the spectrum of an optical frequency comb, which is characterized by an offset frequency and a repetition rate. Furthermore, the apparatus has a phase setter (5), which effects phase setting of the electromagnetic radiation of the pulses laser (1). In accordance with the invention, the offset frequency of the spectral lines of the optical frequency comb is adjustable by time-proportional phase setting by means of the phase setter (5).