A laser source is used in a geodesic device to improve the emission of laser light, in which the laser diodes emitting multimodal radiation are influenced by a mode-selective component such that the laser radiation emitted by the laser source has monomodal character. An edge emitter or a vertical semiconductor emitter with an external cavity, is hence used, in which a mode selective component is arranged, for example, a monomode fibre or resonator mirror, which has the effect of a mode-selective resonator construction. Components with negative dispersion can be used for pulse compression to compensate for the greater pulse duration generated by the lengthened cavity.