Transverse mode characteristics of a high power 1.3µm GaInAsP/InP buried crescent laser by the use of a dry etching process is described. With this technique, a single transverse mode (STM) yield as high as 95% was achieved. Transverse mode stability was confirmed after 1000 h aging at 50, 20 mW. A coupling efficiency into a single mode fiber as high as 63% was obtained.