Research On Biological Sensing Based On THz Metameterial EIT

Biological sensor based on planar terahertz metamaterials, which is one kind of label-free sensor, has attracted much attention from researchers owing to its advantages of high sensing sensitivity and high reliability. This sensor based on the principle of the shift of the resonance frequency has important application future. Up to now, there are two main problems for the research: the quality factor(Q factor) of the resonance in the planar THz metamaterials sensor is not high enough, and lacking of testing system with high THz spectrum resolution. These two problems affected the measurement accuracy, which hindered its practical application.This paper focuses on these two problems, planar terahertz metamaterials biological sensor based on EIT effect, which features high Q resonance, and testing system with high THz spectrum resolution based on the principle of photonmixing is studied. And the main points are as follows:(1) At present, planar terahertz metamaterials sensor, which applied to biological sensing experiment, relies on LC resonance and dipole resonance, and the Q factor of the resonance are all below 10. Based on the EIT effect, DSRR metamaterials biological sensors, with their Q factor higher than 25, are designed. Among them, the highest Q factor reached 34, the sensitivity is 23.7 GHz/RIU(RIU,Refractive Index Unit), and the value of FOM(Figure of merit) is 2.47. In addition, the simulation results show that the sensing performance of EIT resonance is better than that of LC resonant and dipole resonance, and the sensing sensitivity is proportional to the center frequency of resonance peak. This has laid a theoretical foundation for the DSRR planar THz metamaterials sensor applying for biological Detection.(2) A tunable continuous-wave THz radiation and detection system with high spectral resolution, using external cavity semiconductor laser and an interdigited finger bow-tie antenna, has been established based on the principle of photonmixing. The linewidth of THz output is better than 1MHz. The signal-to-noise ratio(SNR) of the system is better than 50 d B at frequency lower than 0.7 THz, and the maximum system SNR of 68 d B is achieved at 0.50 THz. Such technical indicators have reached the advanced level, providing a guarantee for the transmission characteristics measurement of THz metamaterials Biological sensor.(3) A DSRR THz metamaterials sensor, based on EIT effect, with high Q factor is fabricated using photolithography, vacuum coating and lift-off technology. The experimental test result show that its EIT resonance frequency is 0.324 THz and Q factor of 27. The recognition and detection of SA in BAS is realized by DSRR planar terahertz metamaterials biological sensor with Biotin as sensitive element. In the experiment, the minimum frequency shift of EIT resonance is 0.60 GHz while minimum SA concentration of 0.2 mg/m L. In conclusion, the key to improve the sensitivity of the biosensor is to design a planar metamaterials sensor with higher Q factor.