Abstract
To overcome the effect of analyte thickness and limitation of single wavelength sensing, we propose an ultra-sensitive stereo metamaterial biosensor with double resonance frequencies based on coupling electric resonance and magnetic resonance. The electromagnetic analysis demonstrates that the double resonance coupling, induced by the stereo double-layer structure, can significantly improve sensitive biosensing at the terahertz frequency. The results show that by changing the size of the structure, each resonance frequency can be independently tuned in the range of 0.5–1.8 THz and the maximum refractive index sensitivity is 930.4 GHz/RIU. These results have significant implications for the detection of samples with different frequency points. The proposed ultra-sensitive stereo metamaterial structure has excellent potential for application in biomolecule detection and differentiation.
Highlights
Among various optical sensing methods, terahertz (THz) spectroscopy (0.1–10 THz) is considered as one of the most promising tools towards biological sensing, since the fingerprint vibrational frequency of most chemical and biological molecules lies in this spectral region[1,2,3]
We present an ultra-high sensitivity stereo dual-split ring resonator (SDSRR) metamaterial biosensor with two transmission dips, which each dip can be independently tuned at 0.5-1.8 THz
For the SDSRR, the magnetic field plays a predominantly important role in high resonance frequency, but electric excitation can work at low resonance frequency due to coupling effect of the metal slab between the top gap (Tgap) and bottom gap (Bgap), as shown in Figure 4i and 4j
Summary
Among various optical sensing methods, terahertz (THz) spectroscopy (0.1–10 THz) is considered as one of the most promising tools towards biological sensing, since the fingerprint vibrational frequency of most chemical and biological molecules (protein, RNA, and DNA) lies in this spectral region[1,2,3]. The split ring resonators (SRR) is one of the original designs of strong artificial electromagnetic materials in which each SRR consists of two concentric open loops with opposite openings [23] This requires a higher sensitivity of the sensor as the samples being detected becomes more and more microscopic. To making effective use of sensing capability of metamaterial sensors at terahertz frequencies, usually, a large thickness of the analyte is desired In this case, the amplitude of the resonance becomes very weak so that it could be difficult detected in the noisy environment. The threedimensional structure that lifts the split ring from the substrate can greatly reduce the dielectric loss introduced by the substrate, and the three-dimensional structure produces a strong fundamental resonance excited by a pure magnetic field [18] The performance of this structure is much higher than that of a planar SRR sensor. This is the main reason why the SDSRR sensor has much higher sensitivity than that of VSRR structures
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