增透膜的遗传算法设计

Anti-Reflection Coating Designed by Genetic Algorithm

用遗传算法设计了多层光学膜。设计时只要事先确定最大层数，算法就可自动优化选择合适的层数，同样每层的镀膜材料及厚度也由算法自动优化选择。设计中采用了不同以往的评价函数。在LBO（LiB3O5）晶体上用两种评价函数设计了1064nm，532nm二倍频增透膜。前一种评价函数设计的增透膜在1064nm和532nm处的透射率分别达到99．98％和99．99％，后一种评价函数设计的增透膜在两处的透射率均达到100．00％。在K9玻璃上设计了可见光宽带增透膜，450～650nm范围的宽带增透膜的透射率均超过99．91％，390～780nm范围的宽带增透膜的透射率均超过99．30％。采用的评价函数对膜系结构的变化敏感时，用遗传算法设计才有效。

An approach for designing multilayer optical coatings is presented by use of genetic algorithm. With a predetermined maximum layer number, the algorithm automatically specifies the appropriate layer number and material and thickness of each layer. Evaluation function used here is different from the others before. The 1064 nm, 532 nm frequency-doubled anti-reflection coating is designed on LBO （LiB305） substrate with two evaluations functions. Two coating structures are found with high transmissivities, one with transmissivity 99.98% at 1064 nm and 99.99% at 532 nm, the other with transmissivity of 100.00% at both wavelengths. The broad-band anti-reflection coating on K9 glass substrate is designed. The transmissivities of two broad-band antireflection coatings optimized over a range of wavelength （450-650 nm） and （390-780 nm） are above 99.91% and 99.30% respectively. If the evaluation function is sensitive to the deviation of coating structure, the approach by genetic algorithm is effective.