Research On Tunable Terahertz Biosensor Based On Graphene Metamaterials

The fingerprint characteristics of Terahertz（THz）spectrum can provide biomolecule vibration information,which has great application value in the field of biological sample detection.However,the biological sample are weakly interacted with the THz wave propagating in free space,so the signal obtained from the biological sample is weak and cannot meet the needs of detecting trace samples.Metamaterials can effectively enhance the local electric field,and it is very sensitive to the surrounding dielectric changes,and this feature is conducive to improving the biological sample signal.Therefore,metamaterials are widely used in the detection of trace samples,and gradually developed into a new type of sensor device.However,conventional metamaterial biosensors can only detect substances in a certain frequency band,and it is difficult to effectively modulate the design and processing,which is not conducive to the development of practical applications.The study reveals that graphene has high efficiency tunability and can realize the modulation of THz wave.Based on the above reasons,this subject research on tunable THz biosensors relied on graphene metamaterials are as follows:（1）The THz biosensor composed of concentric discs and rings was designed based on the disc-shaped graphene metamaterial.The simulation software was used to analyze and optimize the main structural parameters,and the resonance mechanism and sensing mechanism of sensor was analyzed by simulating the surface current distribution and electric field distribution of the structure.In addition,the influence of the refractive index and thickness of the test object on the sensing performance were calculated and analyzed.In addition,the adjustable ability of THz biosensor performance of metamaterials can be realized in a wide frequency range by the Fermi level of the graphene,and the impact of THz biosensor performance is analyzed via the graphene Fermi level.The results show that the sensor is insensitive to polarization and angle as well as sensitive to changes in refractive index and thickness of the test object.It’s sensitivity is 156.1 GHz/RIU（Refractive index unit）,and Q value is 72.3,and FOM value is 3.3.（2）Since the absorption peak width at half maximum of the metamaterial absorber is very narrow,and at the same time it is very sensitivity to changes in the external dielectric environment,and a THz biosensor based on an absorber-type graphene metamaterial is designed.The main structural parameters are optimized used simulation software,the absorption mechanism and sensing mechanism through the surface current distribution are analyzed,and the influence of the refractive index and thickness of the test object were analyzed on the sensing performance of the biosensor.The dynamic adjusting with the resonance frequency of the biosensor is realized by adjusting the Fermi level of graphene,and the measured range is enlarged.In addition,the effect of graphene Fermi energy level on the performance of metamaterial biosensors was analyzed.The calculation results show that the low-frequency f₁ sensitivity of the biosensor is 305.8 GHz/RIU and the high-frequency f₂ sensitivity is 448.9 GHz/RIU;the quality factors Q at the two resonances are 278.8 and 465,and the FOM values are 61.2 and 96.7,respectively,and the performance of the resonant metamaterial THz biosensor is better than that of the single sensor.