Abstract: An impact resistant anti-reflection coating for an optical element mounted on an airborne system which mitigates damage to the optical element when the airborne system is flown through a high velocity droplet impact medium is described. In a first embodiment, the coating comprises a material having a relatively high modulus of elasticity deposited to a thickness equal to an odd multiple of a quarter of a wavelength of the wavelength radiation to be transmitted through the optical element. In accordance with a further aspect of the invention, the high modulus of elasticity layer may comprise a homogeneous mixture of a pair of high modulus elasticity materials as well as a composite layer comprising a first layer of a high modulus elasticity material and a second layer of a second modulus of elasticity material. In a second embodiment, the outer surface of an infrared material is strengthened by single diamond point turning the outer surface of the material to introduce into the surface a compressive layer.

Abstract: A single crystal Fe film is deposited on a (100) gallium arsenide substrate by ion beam sputtering the Fe film. The sputtered Fe atoms are imparted with energies in the range of about 1 electron volt to at least 10 electron volts to impart sufficient kinetic energy to said ions to allow said ions to have high surface diffusion rates, thereby permitting the atoms to be located at the proper lattice sites of the Fe crystal formed over the gallium arsenide substrate.