Research On Goos-H(?)nchen Shift And Its Sensing Application In Graphene

The Goos-H(?)nchen(GH)shift refers to the lateral shift of a reflected beam between two media interfaces when the incident angle.The GH shift has attracted much attention since its introduction and has been widely used in the fields of precision metrology,nanotechnology,optical switching,optical sensing,and quantum information.Nevertheless,the small GH shift produced at the interface limits its observation and measurement.Graphene is a novel two-dimensional crystal material composed of single atomic layer with excellent electrical and optical properties,so it is expected to improve the control ability of GH shift.In this thesis,the beam transmission characteristics in the graphene structure are systematically studied by adopting the transfer matrix method.On this basis,a series of methods to realize the convenient adjustment and large control range of the GH shift are proposed.These studies are expected to provide theoretical support for the research of the sensing application based on the GH shift.The main results are obtained as follows:Firstly,a new scheme of precisely controlling positive and negative GH shifts in a graphene-substrate system is proposed.It is revealed that the magnitude and sign of GH shifts are closely related to the imaginary part of graphene conductivity,while the Brewster angle position is largely influenced by the real part of conductivity.Further studies show that the magnitude and sign of GH shifts at a certain Brewster angle are changed only by Fermi energy.On the basis of these findings,a scheme to control the positive and negative GH shifts precisely is proposed and demonstrated by instances.Finally,a refractive index detector with adjustable sensitivity coefficient is designed by applying the precise control properties of GH shift.Secondly,a temperature sensing method based on GH shifts with tunable and high sensitivity is proposed by using weak measurement technique.It is found that the GH shifts in graphene-substrate system are sensitive to the temperature,which is caused by the variations of both the conductivity of graphene and the refractive index of the substrate.Combined with the weak measurement technique,a temperature sensing method based on the amplification of GH shifts is proposed.Remarkably,the sensing sensitivity has two orders of magnitude enhancement and also can be controlled by adjusting the amplified angle.Finally,the sensitivity of temperature sensing can be 48.1×10 nm ? by changing the Fermi energy of graphene.Thirdly,a high-sensitivity temperature sensing method is proposed by using a symmetrical graphene-cladding waveguide structure.It is revealed that the GH shifts show a quasi-periodic trend with temperature,and the temperature dependence of GH shifts is mainly caused by the temperature dependence of BK7 glass.Further studies show that the GH shifts is very sensitive to a change in temperature near the resonance angle,and we can enhance the temperature dependence of GH shifts by adjusting Fermi energy.Based on these findings,the sensing region is established near the resonance angle,and then the maximum sensitivity of the temperature sensing-7.6×104?m ? is obtained by selecting the best incident angle and the Fermi energy in the region.