Diode lasers are best-used for conduction mode welding of thin metals. Because of their small size (see Figure 2), diode laser systems can be mounted directly on robot arms and moved relatively quickly. Also called laser diode welding, semiconductor (LD) laser welding is a technique that uses a laser beam generated by an electric current passing through a semiconductor as the heat source. Because the lamp is not used as the excitation source, devices can be compact, and maintenance such as lamp. A diode laser is a semiconductor device that uses a p-n junction to produce coherent light using Light Amplification by Stimulated Emission of Radiation (LASER).