Design And Research Of Graphene-Based Actively Tuned Metamaterial Absorber

Graphene is a high-profile two-dimensional single-layer carbon atomic material.Its excellent photoelectric properties such as high carrier mobility,low loss and surface conductivity tunability make it an important candidate material in the design of nano-optoelectronic devices.The good binding property of graphene can form highly localized electromagnetic fields on the graphene surface,enhancing light absorption and achieving high sensitivity sensing performance.Although some graphene-based adjustable absorbers have been proposed,the defects of these absorbers,such as low absorption efficiency,single resonance mode,complex structure,tedious manufacturing steps and weak sensing performance,have caused great obstacles to the practical application of the absorbers.Therefore,it is necessary to design a graphene-based absorber with simple structure,easy manufacturing,multi-mode resonant absorption and good sensing performance.Anodic Aluminum Oxide(AAO)has simple preparation process,high cost performance,good mechanical properties and thermal stability.It can be used many times and has a lower cost,which facilitates the mass production of absorbers.In order to improve the Q factor of sensor,bound states in the continuous-spectrum(BIC)are introduced into our metamaterial structures.Its ultra-high Q value and narrow linewidth resonance mode help to improve its sensing performance.Based on the above considerations,three different types of graphene-based absorption sensors are proposed in this paper.The Finite-Difference Time-Domain(FDTD)method is used for calculation simulation,and the absorption sensing performance of the three absorption sensors is explored and analyzed.The specific research contents are as follows:(1)A three-band active tunability graphene perfect absorber is proposed in the mid-infrared band.By adjusting the Fermi level of graphene,the active tunability of the absorber can be achieved.Four parameters,sensitivity S,figure of merit FOM,quality factor Q and detection factor P,were calculated to characterize the sensor performance.The sensing properties of the absorbers in different concentrations of solution were simulated respectively,and it was proved that the absorbers have high refractive index sensitivity.In addition,the specific application of the absorber in the measurement of hemoglobin content in vivo is discussed.The results show that the sensing performance of the absorber is good and stable.(2)A graphene-anodized alumina template combined absorber was designed in visible and near infrared bands.By comparing the absorption of different shapes of AAO holes,the circular hole was determined as the best shape.The influence of the thickness of alumina layer and PMMA layer on the light absorption was investigated.The hole radius and lattice period of AAO template were designed to control the leakage rate in the coupling.Then,the sensor performance of the absorber and the application of the absorber for substance detection is analyzed.The results show that the resonant wavelength of the structure designed is highly sensitive to the refractive index of the surrounding medium.(3)A grating-disk graphene sensor based on BIC mechanism is proposed in visible and near infrared bands.By constructing a periodic alternating medium structure in the y direction,the symmetry of the structure is broken under the condition of oblique incidence,thus stimulating the Quasi-BIC mode of the device.The sensor generates six perfect resonant transmission modes at 698.26 nm,734.43 nm,762.37 nm,817.89 nm,921.85 nm and 1016.71 nm.The influences of the period and the thickness of the structure on the resonance mode are studied,and the change of BIC mode when the structure changes is discussed.The maximum quality factor Q(max)of the sensor is calculated to be 3917.68,which proves the excellent sensing performance of the sensor,and is expected to be applied in biosensing,medical imaging and other fields in the future.