The invention relates to a
germanium substrate 8-12 [mu] m
infrared band diaphragm and a preparation method thereof, and belongs to the field of
infrared optics. The diaphragm takes
single crystal germanium as a substrate, and the front and back surfaces of the substrate are plated with the same
infrared antireflection film
system structures; and the structures of the infrared antireflection film systems on the front surface and the back surface are as follows: a substrate / 0.281 Ge / 0.475 ZnSe / 0.4641 Ge / 0.644 ZnSe / 0.578 YbF3 / 0.126 ZnS / air. According to the principle of destructive interference and constructive interference of light, the constructive interference of light can be maximized by using a multi-layer
film structure, so that the
transmittance of the coated lens is maximized. In the aspect of
transmittance, due to the fact that Ge, YbF3, ZnS and other
coating materials have absorption in the light-transmitting
wave band, and meanwhile, tensile
pressure stress between the film
layers also absorbs light in the
wave band, the thickness of the film
layers with absorption is reduced to the minimum, and meanwhile, ZnSe materials with more perfect light-transmitting performance are adopted in the second
coating film and the fourth
coating film, so that the
transmittance is improved, and the light-transmitting effect is improved. And in the film plating process, the film layer stress is reduced by adopting the
modes of
ion source assistant plating and bombardment before and after
ion source plating, so that the film layer strength is enhanced while the absorption is reduced, and the transmittance is improved.