For evaporating a protective coating on a light emitting end surface 51a of a laser chip 51, there is formed first an Si film 52a, which is free from generation of oxygen due to decomposition. Thus, there is created a coating in the vicinity of the light emitting end surface 51a immediately after start of evaporation process under conditions of low partial pressure of oxygen. At the same time, in the later evaporation process of the protective coating 52b, if oxygen is generated due to decomposition of the evaporation material Al2O3, and oxygen partial pressure is increased, collision or bonding of the oxygen with the end surface 51a is prevented, thereby decreasing damages given to the end surface 51a in the process of protective coating creation. Further, the Si film 52a has a film thickness as small as approx. 20 Å. This controls generation of leakage current in the Si film 52a (or the end surface 51a), and prevents negative influence on oscillation characteristics.