A Three-Step Procedure for the Design of Broadband Terahertz Antireflection Structures Based on a Subwavelength Pyramidal-Frustum Grating

作者：Li Xian^*; Hu Xiaokun; Li Yanfeng; Chai Lu

来源：Journal of Lightwave Technology, 2014, 32(8): 1463-1471.

DOI：10.1109/JLT.2013.2296295

• Antireflection structure
• coupled-wave analysis
• subwavelength grating
• terahertz wave
• thin film theory

Materials in the terahertz (THz) region have high refractive indices, thus leading to significant Fresnel reflection loss. We present a step-by-step 2-D THz antireflection grating design procedure using thin film theory and coupled-coefficient-matrix method. A thin film with desirable properties is first optimized by genetic algorithm, and a 'translation' from thin film to multilevel grating is then implemented with the coupled-coefficient-matrix method. A final smoothing step leads to a square-pyramidal-frustum grating. Using rigorous coupled-wave analysis, we demonstrate a subwavelength square-pyramidal-frustum grating based on silicon producing broadband (0.5 to 5 THz) and efficient (transmittance> 95%) polarization-independent antireflection effects. The grating parameters are evaluated, showing that our design is resistant to parameter deviations such as grating depth and incidence angle.

• 出版日期2014-4-15
• 单位天津大学