Since the semiconductor laser has a high conversion efficiency, it has many expectations for effective application. There are increasing application trials of processing at actual factories and jobsites. Moreover, it can currently be used as a heat source to directly conduct processing. This is called direct-diode laser (DDL). However, since there is almost no information regarding the DDL structure and beam mode, there are no scientific documents for the theoretical treatment of this heat source. This is considered to have interfered with the broad application for development. This research establishes the theoretical analysis of the semiconductor heat source for material processing, and we attempted to employ a simulation for processing. To verify the established theory, surface hardening and welding processing were performed as typical processing.

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