Résumé
The GaN photonic platform is of large interest for broadband integrated photonics applications, from near-UV (NUV) to visible and near-IR. A broad set of building blocks can be monolithically integrated, including passive waveguides, couplers, gratings, as well as light emitters. Here we present the latest developments in NUV microlasers and their coupling to gratings and waveguides, based on GaN active layers. We demonstrate two iconic NUV microlasers:(i) a microdisk laser based on GaN/AlGaN quantum wells, coupled to a waveguide and an outcoupling grating. The evanescent coupling from the microdisk to the bus waveguide is carefully controlled through the design of the gap between the resonator and the waveguide [Tabataba-Vakili et al., Opt. Lett. 45, 4276 (2020)](ii) a ridge waveguide polariton laser operating with ultra-short Fabry-Perot ridge cavities (5-60µm). In standard ridge lasers, lasing action can only be reached if the pumped section of a laser is longer than the unpumped (absorptive) section. Here we present how a polariton laser, in a ridge waveguide laser geometry very similar to that of standard ridge lasers, operates on a fundamentally different lasing scheme: lasing action is observed for a pumped length equal to only 15% of the cavity. This evidences the difference between polariton lasers and standard lasers governed by Bernard-Durrafourg condition (population inversion);Both lasers operate around 380nm. They share a large set of photonics building blocks developed onto the GaN photonic platform. Strong efforts are pursued in order to operate these lasers under electrical injection.