Broadband AR coatings on germanium substrates using ion-assisted deposition

A series of five broadband antireflection coatings on germanium substrates was deposited with or without ion-assisted deposition at a substrate temperature of 220 degrees C. Measurements of laser-damage threshold for 10.6- microm 0.1-micros pulses were made on these coatings. Germanium films deposited under simultaneous argon-ion bombardments show higher laser-damage threshold and substantially better durability of the AR coatings on the germanium substrates.