the central layer 10 is produced so as to be as thin as possible the doping must be high enough so as to assure high conductivity the minimum thickness is limited by the manufacturing processes utilized holes which interrupt the central layer 10 must not be present the lower limit of 0 02 u03bcm for the thickness and the upper limit of 20 20 cm 3 for the doping level which are given in table 1 represent the present state of the art lower values for the thicknesses and higher values for the doping of the central layer would be advantageous for the invention the quasi index discontinuity at the edge of the ridge corresponding tot he mcrw principle must be greater the narrower the ridge and thus the narrower the intended emission limitation and this requires adequately small spacing of the layers that carry the emission which are the tuning layer 9 and the active layer 6 from the surface or the boundary surface to the cladding layer 11 and thus these layers must be adequately thin as a compromise the active layer 6 is kept optimally thin so as to maintain a thickness for the tuning layer 9 that is adequate.