Tunable Optical Properties Based On Graphene-hBN

The optical pulse group delay and Goos-H?nchen(GH)shift on the surface of the medium are two typical optical phenomena in the process of beam propagation.Because group delay and GH shift are widely used in controllable delay line,optical sensor and,quantum information equipment respectively.However,due to the limitation of materials and devices,the values of optical pulse group delay and GH shift generated are small by traditional structures,and most of them focus on visible light,optical communication and terahertz band,so there is a lack of research on the infrared band.In recent years,the adjustable and hyperbolic properties of new two-dimensional materials such as graphene and hexagonal Boron Nitride(hBN)have created favorable conditions for the realization of the optical pulse group delay and GH shift in the infrared band.In this paper,based on the tunable properties of graphene and the hyperbolic properties of hBN in the infrared band,the enhancement and regulation of reflection group delay and GH shift are studied.In addition,a high sensitivity refractive index sensor in the infrared band is realized by designing the composite structure of graphene-hBN-bimetal.The specific research work is as follows:Firstly,the transmission matrix method was used to study the adjustable reflection group delay based on the infrared band and based on the graphene/hBN heterostructure.Since the significant Lorentz resonance characteristic of the dielectric constant of hBN in the bands of near 7.28?m and 12.72?m,it is possible to achieve a large optical reflection group delay using the graphene-h BN heterostructure near the Lorentz resonance band.It is shown that the reflected group delay can be effectively enhanced by tuning the Fermi energy or the number of graphene layers.Moreover,by adjusting the incident angle or the thickness of hBN,the reflection group delay can be tuned positive or negative near the incident angle of 47°or the thickness of hBN of128nm.Secondly,the enhanced GH shift is investigated based on graphene-hBN heterostructures in the infrared band by using the transfer matrix method and the steady-state phase method.The theoretical research showed that the GH shifts can be controlled by adjusting the graphene Fermi energy or layer numbers,when the wavelength of transverse magnetic polarized incident light is 12.2?m.In addition,by the hBN thickness around 1.53?m,the positive and negative variation of GH shifts can be switched in the range of-150??150?.Thirdly,a bimetallic sensor based on graphene-hBN heterostructure is theoretically studied.The sensitivity of sensor can be improved by enhancing the GH shift in the infrared band.The theoretical results show that the sensitivity of2.02?10~5?/RIU can be achieved when Fermi energy is 0.2 eV,graphene is monolayer,thickness of gold layer is 20 nm,thickness of silver layer is 15nm and thickness of hBN is 492 nm.In addition,the sensitivity of sensor can be effectively increased by choosing appropriate thickness of gold and silver.