Abstract: The dielectric and/or semiconductor device influences the dispersion of electromagnetic radiation within a given spectral range. It comprises a substrate being essentially transparent to said electromagnetic radiation. The substrate has a first surface for incoupling said electromagnetic radiation into said substrate, and a second surface. The device further comprises a reflective multilayer structure on said second surface, said multilayer structure providing a controlled dispersion characteristic upon reflection of said electromagnetic radiation, e.g., a chirped mirror. The device is arranged in such a way that there is essentially no interference of electromagnetic radiation propagating in the direction of said multilayer structure and electromagnetic radiation reflected by said multilayer structure. An antireflection coating may be provided on the first surface of the substrate. With this device, oscillations in the group delay dispersion can almost completely be avoided.