Research On Terahertz Absorption And Sensing Properties Based On Metamaterials

The Terahertz（THz）wave has attracted great attention due to its unique characteristics of low loss and low photon energy.It has become a research hotspot in physics,chemistry,electronic information,life science,material science,astronomy and other fields.In terms of non-invasive detection,terahertz（THz）sensor also shows superior performance compared with visible and infrared region.As an important part of terahertz detection technology,the performance of the sensor will greatly affect the use of the whole detection system.But so far,the quality factor（FOM）of terahertz sensor is very low due to the weak radiation and absorption loss.Metamaterials,as an artificial electromagnetic medium,can break through the shackles of electromagnetic properties of materials by artificial construction,and produce unique adjustable electromagnetic response to incident radiation.The birth of metamaterials provides a new idea for the construction of terahertz sensors.Terahertz sensors based on metamaterials are favored by researchers due to their low cost,simple fabrication process,superior performance and few restrictions.In view of the lack of excellent sensors in terahertz technology,this then’s uses theoretical analysis and numerical simulation methods to explore the physical mechanism of the artificially built metamaterial terahertz absorber and its potential application to improve the performance of the sensor.This then’s focuses on terahertz multi band absorber based on metamaterials.Firstly,this then’s selects the perfect terahertz metamaterial absorber composed of four layers of periodic structure composed of gold（Au）and silicon dioxide（Si O₂）with perfect processing technology and stable properties,which are alternately distributed and stacked in the vertical direction.Using the finite-difference time-domain method,the near perfect narrow-band absorption of five frequency bands is realized in the range of 0.9-1.2 THz,resulting in excellent sensing performance.Secondly,the electromagnetic field distribution of each unit of the absorber under the incidence of terahertz wave is obtained by using the finite difference time domain（FDTD）simulation.Combined with the electromagnetic resonance theory and simulation results,we describe the formation mechanism of multi band absorption,optimize the structural parameters combined with Mie resonance theory,increase the FOM to 1792,and realize the ultra-high sensitivity multi band absorber based on metamaterials.Finally,based on the proposed terahertz absorber composed of three-layer periodic structure,this then’s deeply analyzes the influence of silica film coating on Mie resonance.The gain effect and reason of mien resonance excited by silica film on the fifth resonance peak are described.Without affecting the transmission effect of other peaks,a method to enhance the absorptivity of absorption peaks and sensing performance is proposed.