Abstract: In a single-frequency laser and amplifier system, the radiation of a single-frequency, diode-pumped solid-state laser, preferably of a low power microcrystal laser or a monolithic ring-laser consisting of rare-earth-doped or transition-metal-doped crystal or glass materials, is coupled into a semiconductor amplifier chip (preferably GaAlAs, InGaAs or InGaAsP). The material system and the epitaxial structuring of the amplifier chip are selected to adapt it to the emission wavelength of the solid-state laser, so that it amplifies the single-frequency radiation of the solid-state laser and therefore generates an output beam which is intensified with respect to the coupled-in laser radiation.