各向异性超材料中太赫兹波的偏振转换

Polarization conversion of terahertz wave in anisotropic metamaterials

各向异性超材料可以控制太赫兹波的偏振态,实现入射太赫兹波的偏振转换。为了获得非手性各向异性超材料的透射响应与本征偏振复透射系数的关系及其入射偏振依赖性,在太赫兹时域光谱系统中测量了等臂长L形结构超材料在不同偏振角下的正入射透射谱,获得并分析了透射太赫兹波的偏振转换率和偏振态,所得结果与基于琼斯矩阵和坐标变换计算的结果一致。在0.7 THz^1.3 THz频率范围内可实现约20%的偏振态能量转换效率。在L结构和双L结构的偏振转换透射谱中分别观察到了宽带响应和多频共振响应,表明结构改变对太赫兹波透过特性的敏感性和可操控性。所得到的结果可用于太赫兹功能器件的设计、表征和优化。

Anisotropic metamaterials can be utilized to manipulate the polarization states of terahertz waves, and realize the polarization conversion. In order to obtain the dependence of transmission properties of achiral anisotropic metamaterials on the complex transmission coefficients of eigenmodes and incident polarization angles, transmission spectra of L-shaped metamaterials at different polarization angles are measured using terahertz time-domain spectroscopy. Consistent results are obtained through analytical calculation based on the Jones matrix and coordinate transformation. The polarization conversion rates and polarization states of transmitted terahertz waves are obtained and analyzed by the complex transmission coefficients of eigenmodes. A flat polarization conversion efficiency of about 20% is demonstrated in the frequency range 0.7 THz-1.3 THz. In addition, the cross-polarized transmission spectrum of L-shaped metamaterials is compared with that of double L-shaped metamaterials. Broadband and multiband responses are observed, respectively. The results can be used for design, characterization and optimization of various terahertz functional devices.