Power and precision
These incredible advances in semiconductor laser technology enable the development of direct diode lasers (DDLs), including high-power direct diode lasers (HPDDLs) that produce multi-kilowatt output power. DDLs combine numerous diode bars with beam shaping optics, control electronics and a cooling unit. Technology advances now enable DDLs to generate output power exceeding 20 kW in multi-mode systems and produce multi-kilowatt power at higher beam quality than before. In addition to DDLs, companies like Laserline (Germany) offer diode lasers coupled to active fiber converters, which produce 4-6 kW output power at an excellent beam quality of 4-6 mm mrad.
Dramatic improvements in beam quality now enable users to focus laser light to a small point, and this revealed DDLs as rapidly evolving tools for processing metal, plastic and composite materials. In applications like laser welding, which require high precision and deep penetration, DDLs can now compete with fiber lasers. While DDLs directly convert electricity to laser light, fiber lasers are based on rare-earth metal doped optical fibers, which must be optically pumped (energy input) via laser diodes or diode bars. The unit price of a DDL is significantly lower than a fiber laser for CW output power up to 1 kW. In 2018, the typical unit prices were $20,000 for a 1 kW HPDDL and $25,000 for a 1 kW fiber laser, as quoted by key player companies interviewed by IDTechEx. The difference in price between DDLs and fiber lasers is larger at sub-kilowatt output power. Additionally, the wavelengths offered by DDLs are different to fiber lasers, which means that DDLs can process materials with matching absorption spectra more efficiently.