通过对主膜系添加匹配层并借助计算机对膜系进行优化,设计出结构规整、性能优良的1064 nm倍频波长分离膜。用电子束蒸发及光电极值监控技术在K9玻璃基底上沉积薄膜,将样品置于空气中在260 ℃温度下进行3 h热退火处理。然后用Lambda 900分光光度计测量了样品的光谱性能;用表面热透镜(STL)技术测量了样品的弱吸收值;用调Q脉冲激光装置测试了样品的抗激光损伤阈值(LIDT)。实验结果发现,样品的实验光谱性能与理论光谱性能有很好的一致性,退火前后其光谱性能几乎没有发生温漂,说明薄膜的温度稳定性好;同时退火使样品的弱吸收减小,从而其激光损伤阈值提高。理论和实验结果均表明,对主膜系添加匹配层的方法是1064 nm倍频波长分离膜设计的较好方法。

A harmonic beam splitter with a simply regular structure and good optical characteristics was designed by adding matching layers between the basic stack and its media and optimizing with a computed-aided film stack design procedure. Coatings were deposited on K9 glass substrates by electron beam evaporation and photoelectric maximum control method, and then annealed in air at 260 ℃ temperature for three hours. The optical properties of coatings were characterized with a Lambda 900 spectrophotometer, the weak absorption of coatings was measured by surface thermal lensing technique (STL), and laser-induced damage threshold (LIDT) was assessed using 1064 nm Q-switch pulsed laser at a pulse length of 12 ns. It was found that a good agreement between the theoretical and the experimental transmittance was obtained, there was almost no shift for the center wavelength after annealing at 260 ℃, which showed the sample had a good temperature stability, the absorption of the coating decreased after annealing, and a remarkable increase of LIDT was found with the decrease of absorption. The experimental results as well as the theoretical ones indicated that it was a good method to add matching layers to the basic stack for a harmonic beam splitter at 1064 nm.