A Study Of The Gooss-Hanshin Shift In Multi-level Coherent Media

When a light beam incidents on a boundary of media with different refractive indices,the centroids of the reflected and refracted beams are different from that of the incident beam.The small lateral displacement in the incident plane is Goos-H?nchen shift.A light beam with finite width has different plane-wave components.According to Fresnel equations,the reflected beam or refracted beam is a superposition of all the components with different transverse wave vectors,with each component undergoing a different phase change.As a result,a lateral shift occurs to the centroid of the reflected or refracted beam,of which the magnitude and direction are related to the slope of the phase of the reflection or transmission coefficient.Goos-H?nchen shift is sensitive to the optical properties of medium and the structure of the device,and therefore,tiny displacement,change of refractive index and temperature can give rise to a large change of lateral shift of light beam.Hence,Goos-Hanchen shift has potential applications in optical sensing and precious measurement.Quantum coherence effect resulting from the interaction between light and multi-level atoms has significant effect on the optical properties of medium,such as absorption,refractivity,nonlinearity.Recently,quantum coherence effect was used to control the Goos-H?nchen shift.In coherent media,the intensity of light field as well as its phase has impact on the absorption and dispersion.In this thesis,we investigate the amplitude and phase control of Goos-H?nchen shift in two different coherent media.(1)We studied the Goos-Hanchen shift of a light beam incident on a diamond dielectric slab.In a static magnetic field,the ground level of NV center is split because of Zeeman effect.An elliptically polarized light acts as the control field,of which the two circular polarized components respectively drive the transitions between the sublevels ms=±1 and the excited states.A weak probe field couples the transition between ground level ms=0 and the excited states.Therefore a four-level atomic system with tripod configuration forms.When the probe field is resonant with the slab,we obtain large lateral displacements for both the reflected and transmitted light beams.In the case of resonance,the magnitude of Goos-H?nchen shift has a negative correlation to the absorption of medium,while the resonant angle changes with the refractive index of medium.Based on quantum coherence effect,the Rabi frequency of control field,the phase difference of two circular polarized components and the strength of magnetic field have impact on the complex dielectric constant of diamond with NV centers.Therefore,the Goos-Hanchen shift and the resonant angle can be effectively controlled.Under certain parameters,the reflected beam undergoes significantly enhanced lateral displacement.Compared with the widely used sandwiches structure,i.e.dielectric slab-coherent medium-dielectric slab,the NV center system is more compact and simple,and therefore we can explore it to devise new type of photonic device to control the displacement of light beam.(2)We proposed a coupled system,in which a five-level coherent medium is sandwiched between two prisms,to realized phase control of Goos-H?nchen shift.In the atomic system,four control fields drive four excited states and therefore a diamond-type closed loop forms.A weak probe field acts on the ground level and the closed loop.The Rabi frequencies and the relative phase of control fields have impact on the absorption and dispersion of the medium as well as the phase of the reflection/transmission coefficients to the probe field.Therefore,the lateral displacement of light beam can be manipulated.The Goos-Hanchen shift of reflected beam is sensitive to the system parameters,while the change of the transmitted beam is not obvious.Whenthe probe field is resonant with the cavity formed by the two prism,Goos-H?nchen shift is large.The resonant angle and the corresponding lateral displacement are related to the intensity and phase of the control field.Then we can conveniently control Goos-Hanchen shift.The results are useful to the devise of new type of photonic device,such as switching for light beam.