Hass G, Heaney J B, Herzig H, Osantowski J F, Triolo J J
Appl Opt. 1975 Nov 1;14(11):2639-44. doi: 10.1364/AO.14.002639.
A technique for producing adherent and well-protected front surface Ag mirrors with an evaporated Al(2)O(3) + SiO(x) overcoat and an evaporated Al(2)O(3) underlayer is described. A thin Al(2)O(3) layer promotes adhesion between the Ag film and its substrate. The optimum thickness of each outer layer necessary to give good adhesion and protection to the Ag surface with minimal loss in reflectance due to ir absorption was found to be about 300 A for the Al(2)O(3) layer and between 1000 A and 2000 A for the SiO(x) film. Ag surfaces coated in this fashion retained a normal incidence reflectance in excess of 95% over the wavelength region from 450 nm to the far ir, even when exposed to harsh sulfide and humidity environments. Calculations demonstrate the advantage of using protected front surface Ag in comparison to more durable metal reflectors, such as Al or Rh, in terms of high reflectance and low visible region polarization. However, a very pronouncedrestrahlen reflectance and absorption effect in the thicker SiO(x) film is responsible for a calculated drop in reflectance from 98.5% to about 65% at lambda = 8.1 mum and 45 degrees incidence for the Ag + Al(2)O(3) + SiO(x) coating.
描述了一种制备具有附着性好且保护良好的前表面银镜的技术，该银镜带有蒸发的Al₂O₃ + SiOₓ外涂层和蒸发的Al₂O₃底层。薄的Al₂O₃层可促进银膜与其基底之间的附着力。为了在因红外吸收导致反射率损失最小的情况下，给银表面提供良好的附着力和保护，发现Al₂O₃层的最佳厚度约为300埃，SiOₓ膜的最佳厚度在1000埃至2000埃之间。以这种方式涂覆的银表面，即使暴露在恶劣的硫化物和潮湿环境中，在450纳米至远红外的波长范围内，其垂直入射反射率仍超过95%。计算表明，与更耐用的金属反射镜（如铝或铑）相比，使用受保护的前表面银镜在高反射率和低可见光区域偏振方面具有优势。然而，较厚的SiOₓ膜中非常明显的剩余射线反射率和吸收效应，导致对于Ag + Al₂O₃ + SiOₓ涂层，在波长λ = 8.1微米、入射角为45度时，计算得到的反射率从98.5%下降到约65%。
