For achieving balance between manufacturing effort and spectrometer accuracy, a spectral decomposition device is not completely integrated into a substrate stack, but, for example, after manufacturing the substrate stack in the manufacturing process, the opportunity of compensating inaccuracies in substrate stack manufacturing is given by mounting a component with a suitable optical functional element to a window, like, e.g., an entry, exit or intermediate window of the substrate stack, to at least partially cover the respective window, wherein the optical functional element is, for example, an entry aperture, an exit aperture or also part of an optics or an optical element having a spectrally decomposing effect. The substrate stack may be manufactured on wafer level and the manufacturing tolerances in this manufacturing may be loosened, as the subsequent substrate stack-individual mounting or even window-individual mounting of the components may compensate the fluctuations which resulted in substrate stack manufacturing.