Magnetron Sputtered DLC Coatings for KCI Optics for High Power Industrial CO2 Laser

Abstract

Magnetron Sputtered DLC has been studied for possible applications for anti-hygrosity protective coatings of KCI IR optics for high power industrial CO2 laser. Absorption coefficient of sputtered DLC was shown to vary with sputtering parameters and hydrogen content in the deposition environment. By proper control of paramers DLC with absorption coefficient as low as 80cm−1 at 10.6um is obtainable. Laser damage due to pulsed and continuous CO2 laser was studied. Damage threshold due to pulsed CO2 laser was 4–7 GW / cm2, which was relatively insensitive to sputtering power. Damage threshold due to cw CO2 laser for DLC prepared at favourable conditions was shown to be 7.2–7.4 KW / cm2, which was very sensitive to sputtering parameters and the cleaness of the film surface and defects in the film and in KCI substrate. Damage behaviour of DLC has been studied in detail. DLC protected KCI focusing lense (Φ50mm, f= 200mm) has been successfully used for industrial kilowatt CO2 laser processing machine at 1.5KW power level for months long period in a humid atmosphere in shanghai, China.