Amazing technological progresses have been made in the high-power laser field in the last few decades, thus allowing laser systems to be used in several applications, ranging from materials processing (cutting, marking, welding etc.) to biomedical and military sectors. Before the last decade, laser material processing was dominated by CO2 lasers. However, due to their very low wall plug efficiency (amount of electrical power converted into optical) and mechanical reliability issues, CO2 lasers have been replaced by fiber lasers, which are pumped by high power laser diodes (HPLDs). HPLDs are characterized by compactness, high efficiency, high reliability and low ownership costs.