GaAs/GaAlAs laser diodes with reactive ion etched facets have been demonstrated for the first time with high output powers (5 W from 100‐&mgr;m‐wide apertures), high output power density (15 MW/cm2), and high slope efficiencies (66%) in junction‐up configuration under quasi‐cw operation. Mirror etching was performed in a pure SiCl4gas environment by maintaining a low background pressure and gas pressure. High quality etched facets have been achieved with almost no scattering loss.