硫化锌透镜中长波红外宽带增透膜的研制

硫化锌(ZnS)透镜由于其透光区域较宽，便于光学系统的装校而被经常应用于红外光学系统中，但是其作为基底，镀制中长波红外增透膜却具有相当大的难度，尤其是牢固度的问题。根据任务要求研制的增透膜是在3．5～3．9μm的中波红外波段及9～12μm的长波红外波段，平均透射率大于90％。由于长波红外区可选用的宽透射区材料较少，所以兼顾材料的选用、光谱特性及可靠性满足使用要求等几方面考虑，最终采用氟化钇(YF3)作为低折射率材料，经过多次实验，采用混蒸、离子辅助等工艺方法以及选取合适的基底温度，通过对其他工艺环节的不断改进，解决了在ZnS透镜上镀制宽带增透膜，由YF3膜层严重的应力作用而导致膜层龟裂的问题，最终研制成功符合使用要求，并且可靠性和光谱特性皆优的中长波红外增透膜。

Design and Deposition of Broadband IR Antireflection Coatings on ZnS Lenses

Infrared (IR) antireflection (AR) coatings are indispensable to optical and electrooptical system, especially to the systems such as IR camera. They are very important for the system to improve the energy output and the optical performance. ZnS is usually used to make lenses for IR systems because of its wideband transmission region. But as a substrate, it is very difficult to deposit AR coatings on ZnS in IR region, especially for the durability. The AR coating is for the ranges of 3.5～3.9 μm and 9～12 μm, and the transmittance required of the spectra is more than 90%. Because there are very few materials that have a wideband transparency available for the long wavelength IR region, it is much more difficult to obtain a good coating which has both good transmittance and good durability. Giving attention to both choosing IR coating materials and meeting the spectra requirement, yttrium fluoride (YF3) was adopted as low-index material at last. But the severe stresses of YF3 would result in chapping if there was not a suitable depositing condition. This problem was solved by utilizing improved techniques such as mixed-vaporizing, ion beam assisted deposition and feasible temperature. The durability, stability and transmittance are all advanced.