提出了一种新型的纳米级旋转共轭希腊十字型手征结构，并对该结构上下两层希腊十字的旋转角度进行了优化；数值模拟了该结构对不同频率入射波的透射和反射响应，发现透射谱在频率为145和300 THz处存在两个明显的谐振点。通过对透射反射谱的反演，计算了结构的圆二色性、旋光角，得出该结构在谐振频率附近具有很强的旋光性，最大旋光角达到了95°。分析了折射率、相对介电常数、相对磁导率和手征参数，发现这一结构在谐振频率附近分别实现了左旋圆极化波和右旋圆极化波的负折射率，且进一步证明了手征结构实现负折射率的主要原因是大的手征参数。

A new nanometer twisted conjugated gammadion chiral structure is proposed, and the twisted angle of upper and lower layers of the structure is optimized. The transmission and reflection spectra for the incident wave with different frequencies are obtained from numerical simulations. The resonance dips of the transmission spectra at the frequencies of 145 and 300 THz are observed. The circular dichroism, polarization azimuth rotation angle are calculated from simulated transmission and reflection spectra. The results show that the larger circular dichroism and exceptionally strong optical activity are found at the resonance frequency region. The maximum polarization azimuth rotation angle θ can reach 95°. Then the effective parameters of the structure, including relative permittivity, relative permeability, chiral parameter and refractive indexes, are retrieved from simulated transmission and reflection spectra. It is found that the negative refractive indexes of the right-handed circularly polarized and left-handed circularly polarized waves of the structure can be realized at the resonance frequency region. The numerical results demonstrate that the negative refractive index of the chiral metamaterial is due to the large chiral parameter.