Suitable for focusing high power laser light more than 5kW. Copper (Cu) is used mainly since it is superior in heat conductance and can be processed by ultraprecision cutting. In addition, Aluminum (Al) may be used for parts which need to be lightened. For the surface coating, Gold (Au) is used commonly because it has good reflectivity, heat conductance and durability. In addition, Molybdenum (Mo), which has a high melting point and high hardness as its material characteristics, is used for parts where adhesion back-splatters is drastic.