Calculation of vectorial diffraction efficiency of subwavelength blazed gratings
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摘要: 将矢量衍射数值算法严格耦合波分析用于精确计算亚波长闪耀光栅的衍射效率,并分析其衍射特性。建立了闪耀光栅的电磁介质模型,并将楔形不规则结构简化为多层矩形光栅结构,通过电磁场的介质分布建立严格耦合波方程。根据边界条件求解出各层的电磁场分布,再通过增透矩阵方法将各层电磁场依次迭代,求解出了整个结构的衍射效率。计算分析显示,对闪耀角为11.3、周期为500 nm的金属铝闪耀光栅可以得到高于90%的衍射效率和相应的闪耀级次。实验表明这种矢量衍射数值算法具有较高的准确性,可以推广应用于高致密刻线复杂光栅的衍射计算分析。Abstract: The vectorial diffraction numeric algorithm, Rigorous Coupled Wave Analysis(RCWA), was introduced, and it was used to calculate the diffraction efficiency of a subwavelength blazed grating precisely and to investigate the diffraction characteristics. Firstly, the electromagnetic medium model was created, and the irregular structure was simplified into a multi-layer rectangle grating. The rigorous coupled wave equation among the electromagnetic field was built, and the electromagnetic distribution based on the boundary conditions was solved. After that, enhanced transmittance matrix approach was employed to iterate the results between layers, and finally the diffraction efficiency of the whole structure was solved. Calculated results show that the diffraction efficiency of aluminium film grating with the blazed angle of 11.3 and a period of 500 nm is higher than 90% and can also offer a relative blazed order. This numerical vectorial diffraction algorithm has a good precision and wider applications in the calculation of the high and compact complicated grating.
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