Laser source with a germanium-based suspended membrane and an integrated waveguide that participates in forming the optical cavity

A laser source, comprising:

• a germanium-based semiconductor layer comprising a membrane suspended above a carrier layer, the suspended membrane being formed of:
• a central portion, which is tensilely stressed in a plane parallel to the carrier layer, comprising an optical amplification section that is configured to produce light radiation by stimulated emission, and
• a plurality of lateral portions forming tensioning arms that are opposite one another with respect to the central portion, and that are arranged so as to keep the central portion suspended and tensilely stressed, the tensioning arms having an average width larger than an average width of the central portion,
• an integrated waveguide that participates in forming an optical cavity with at least the optical amplification section, said integrated waveguide being located level with the carrier layer and at distance from the suspended membrane, and comprising:
• a coupling section, which is located facing the optical amplification section, and which is configured to allow evanescent-wave optical coupling to the optical amplification section, and
• at least one curved section that extends the coupling section, and which is arranged so that the integrated waveguide is placed at distance, in orthogonal projection, from the tensioning arms,
• wherein the coupling section comprises at least one coupling zone that has a transverse dimension that varies along the longitudinal axis of the integrated waveguide, so that an effective index of the optical mode supported by the coupling section passes locally from a value higher than an effective index of the optical mode supported by the optical amplification section to a value lower than the effective index of the optical modes supported by the optical amplification section.