利用等效层的消偏振宽带减反膜设计

Design of Non-Polarizing Broadband Antireflection Coating Using Equivalent Layer

分析了倾斜入射条件下导致光学薄膜产生偏振的原因,针对不同偏振态的等效导纳与等效相位进行了分析,并计算了对称膜层在45°入射条件下不同偏振态的等效折射率与等效相位厚度,采用等效层方法设计了光学性能良好的600～900 nm波段消偏振宽带减反膜。最后利用电子束蒸发技术制备了薄膜样品,样品的光谱性能完全能够满足使用要求。其中在600～900 nm波段范围内,平均反射率均小于1．38%,反射率的偏振度均低于0．89%。另外,通过对其理论及实验光学性能、角度敏感性、膜层厚度误差敏感性等方面的分析结果可知,对称膜层组合法是设计消除倾斜入射下宽带减反膜偏振效应的一种行之有效的方法。

The reasons leading to polarization for optical coatings at oblique incidence were analyzed. Analysis was made for the equivalent admittance and phase of different polarization states, and the equivalent indices and phase thickness for both polarizations of a symmetrical structure at 45° incidence were computed. Then a non-polarizing broadband antireflection coating with good optical performance within 600- 900 nm was designed by using equivalent layer method. A sample was fabricated through electron beam evaporation technique, and its optical performance absolutely satisfied the requirements. From 600 to 900 nm, the average reflectance was less than 1.38%, and the polarization of reflectance was lower than 0. 89%. In addition, after analyzing its theoretical and experimental performance, angle sensitivity and layer-thickness error sensitivity, we drew a conclusion that symmetrical layer combination was a practical way to design a non-polarizing broadband antireflection coating at oblique incidence.