Jingya Xie, Xi Zhu, Xiaofei Zang, Qingqing Cheng, Lin Chen, Yiming Zhu,
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| Fig. 1 Schematic illustration of (a) the experiment setup, (b) optical image of the metamaterial with L-tartaric acid deposited on it, and (c) the SRR unit cell. |
We present metamaterial-enhanced terahertz vibrational spectroscopy to solve the low sensitivity problem of the THz ray absorption detection in molecular and biomolecular thin film. In a proof-of-principle experiment, we demonstrate the system in split ring resonators (SRRs) metamaterial that is strongly coupled to L-tartaric acid molecular under a low-temperature condition. The experimental results show that the extinction ratio of the detected signal can be significantly improved from 1.75 dB to 4.5 dB. The numerical calculations confirm and explain the experimental observations. By detuning the resonance of metamaterial, the behavior of the spectral signal is modified. When the SRRs and molecular vibrational resonance frequencies are closely aligned, a clear mode splitting is observed resulting in a transparency transmission with enhanced extinction ratio. This method shows great potential for application in thin film sensing by detecting molecular vibrations in the lower-energy terahertz region.
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