Research On Dynamic Modulation Characteristics Of Terahertz Metamaterals Based On Graphene Plasmon Induced Transparency

As an atom-thin layer,graphene and its plasmon are very sensitive to the immediate environment.Graphene plasmons strongly couple to molecular vibrations of the adsorbates,and lattice vibrations of other atomically thin layer.Graphene metasurface emerged as an attractive material for sample detection.On the other way,due to their low loss subradiant behavior,plasmon induced transparency(PIT)allows excitation of high-quality(Q)factor resonances.Graphene plasmon induced transparency(GPIT)has great prospects for developing label-free terahertz biosensor.Baesd on the graphene plasmon induced transparency structure,several new dynamic terahertz metamaterials are designed and studied,and their application mechanism in label-free terahertz biosensor are discussed.The details of my work are listed as following:1.The dynamic electrical characteristics of GPIT structure in terahertz modulator are investigated.By tuned the Fermi level of the T-shape graphene strip through electrostatic gating,the amplitude modulation depth of the peak frequency in the transparent window and the peak frequency modulation range in the transparent window are discussed.The coupled Lorentz oscillator model is applied to well explain the formation mechanism of GPIT.Meanwhile,the dynamic adjustable properties of the maximum group velocity refractive index in the transparent window is investigated by the coupled Lorentz oscillator model.2.The physical mechanism of the terahertz dual band perfect absorber,based on the periodically patterned elliptical nanodisk graphene structure,is investigated.The polarization and incident angle of the incident terahertz light influenced on the absorption peak are discussed.The dynamic tunable properties of resonance absorption are discussed by changed the the Fermi level and the carrier relaxation time of graphene,respectively.3.The physical mechanism of the terahertz perfect absorber based on GPIT structure is investigated.The absorption bandwidth is researched through changing the Fermi level of the T-shape graphene strip under different incident electric field polarization.Finally,an absorber circuit model for graphene metasurface is proposed,based on the Lorentz function spectrum,which provides theoretical guidance for the design of terahertz perfect absorber.4.The physical formation mechanism of graphene plasmon-induced polarization conversion is analyzed.The dynamic modulation characteristics of the transparent window are studied by tuned the Fermi level of T-shape graphene strip through electrostatic gating.At the same time,the polarization state of the transmitted light at different Fermi level and carrier relaxation time are discussed,respectively.The dynamic tunable range of the group velocity refractive index in the transparent window is obtained by solving the coupled Lorentz oscillator model.