Research and Development of Optical Waveguides and Elements Using Anodically Oxidized Alumina Thin Film

我们研究了阳极氧化氧化铝薄膜的光学性质，并从理论上和实验上证明了它们是小而高效的光学元件的有前途的材料。采用铝基阳极氧化法制备了30 ~ 100 μ m厚度的阳极氧化氧化铝薄膜。在浓度为20 ~ 30%的硫酸中，以50 mA/cm^2的电流对铝进行阳极氧化时，光损耗最低，在200 ~ 300‰的温度下退火可进一步降低光损耗。我们用双豆干涉法检测了氧化铝薄膜，发现折射率随着与衬底距离的增加而减小。这种现象在阳极氧化时间较长的薄膜中更为明显。在0.63 nm波长处，水封氧化铝膜的双折射率可达4 × 10^<-3>。通过在氧化铝膜的圆柱孔中电镀镍，制备了微偏振器。在1.3 μ m波长处，消光比为- 30db。在大电流阳极氧化的氧化铝膜中也发现了极化功能，其中存在阳极氧化过程中未氧化的残余铝柱。从理论上计算了阳极氧化氧化铝薄膜的光学损耗和折射率。该理论很好地解释了实验结果，并为设计新型光学元件提供了指导。

We have studied the optical Properties of anodized alumina films and demonstrated both theoretically and experimentally that they are promising materials for small and efficient optical elements:1. We have fabricated the anodized alumina films of 30-100 mum thicknesses m u by anodic oxidation of aluminum substrates. The optical loss becomes lowest when the aluminum is anodized with an electric current of 50 mA/cm^2 in the sulfuric acid of 20- 30 %, and the loss is reduced further by annealing the film at 200-300 ﾟC.2. We have examined the alumina films by two-bean interference and found that the refractive index decreases as the distance from the substrate increases. This phenomenon becomes more eminent in a film of longer anodization time. It has also been found that the water-sealed alumina film has birefringence as large as 4 X 10^<-3> at the wavelength of 0.63 mum.3. We have fabricated a micropolarizer by electroplating nickel into the cylindrical pores in the alumina film. An extinction ratio of - 30 dB has been obtained at the wavelength of 1.3 mum. Polarizing function has also been found in the alumina film anodized with a large electric current, where there are residual aluminum columns that are not oxidized in the anodization process.4. We have calculated theoretically the optical loss and refractive index of the anodized alumina film. The theory explains the experimental results well and gives a guideline for designing novel optical elements.