A photonic circuit with a hybrid III-V on silicon or silicon-germanium active section, that comprises an amplifying medium with a III-V heterostructure (1, QW, 2) and an optical wave guide. The wave guide comprises a coupling section (31) facing a central portion of the amplifying medium, a propagation section (34, 35) and a modal transition section (32, 33) arranged between the coupling section and the propagation section. In the modal transition section, the optical wave guide widens progressively from the propagation section towards the coupling section.