Integrated semiconductor structure with optically coupled laser diode (11) and photodiode (12A), both devices having etched, vertical facets (16A, 21). The photodiode has a spatially non-uniform sensitivity profile with respect to the incident light beam (18A) emitted by the laser. This is due to the varying distance from the laser facet and/or to variations in the angle of incidence and results in photocurrents produced by the photodiode that depend on the intensity distribution of the light beam. The spatially non-uniform sensitivity profile allows the measurement of the far-field intensity distribution of the laser and thus on-wafer screening of lasers with respect to their mode-stability.