Chirality (C) is a fundamental symmetry property of objects. Detecting and distinguishing molecular chirality in the infrared spectrum is important in life sciences, biology, and chemistry. In this paper, we demonstrate an achiral metasurface based on a gaped dual-germanium-dimer array for enhanced mid-infrared chiral sensing under both circularly polarized light (CPL) and linearly polarized light (LPL) excitations. With the metasurface, strong electric and magnetic dipole resonances with large field enhancement can be generated, resulting in an accessible superchiral hotspot in the dimer gaps under both excitation modes. The maximum electric and magnetic field enhancements exceed 220 and 100 for the bare metasurface, and exceed 70 and 60 for the metasurface coated with a 50 nm chiral biolayer under both excitations, respectively. Importantly, a high volume-averaged C enhancement C E_ave of 241 (444) and C E_ave_bio of 161 (102) under CPL (LPL) excitation can be achieved for the bare metasurface and it coated with the chiral biolayer, respectively. These results may open up new possibilities for ultrasensitive vibrational circular dichroism (VCD) and rotational optical dispersion (ORD) spectroscopy in the mid-infrared range.

中文翻译：

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用于在两种激发模式下增强中红外手性传感的介电双二聚体超曲面

手性 (C) 是物体的基本对称性。检测和区分红外光谱中的分子手性在生命科学、生物学和化学中具有重要意义。在本文中，我们展示了一种基于带间隙双锗二聚体阵列的非手性超表面，用于在圆偏振光 (CPL) 和线偏振光 (LPL) 激发下增强中红外手性传感。利用超表面，可以产生具有大场增强的强电和磁偶极子共振，从而在两种激发模式下的二聚体间隙中产生可接近的超手性热点。在两种激发下，裸超表面的最大电场和磁场增强超过 220 和 100，而涂有 50 nm 手性生物层的超表面分别超过 70 和 60。重要的，C增强C E_ave 241 (444) 和C E_ave_bio 在 CPL (LPL) 激发下，裸超表面和涂有手性生物层的 161 (102) 可以分别实现。这些结果可能为中红外范围内的超灵敏振动圆二色性 (VCD) 和旋转光学色散 (ORD) 光谱开辟新的可能性。