A Study Of The Goos-Hanchen Shift And The Imbert-Fedoroff Shift In Coherent Atomic Media

The Snell law and Snell formula are usually used to describe the reflection and refraction of light when it propagates from one medium to another.The actual reflection and refraction points have a movement compared to the points predicted by geometric optics when the reflection and refraction occurs at the interface of the two dielectrics due to the limited width of the actual beam,the longitudinal shift is called the Goos-Hanchen shift(GH shift)and the transverse shift is named the Imbert-Fedorov shift(IF shift).With the research of the GH and IF shifts in various materials or structures,it is found that the shifts are particularly sensitive to the refractive index,absorption dispersion,and structural properties of media.Based on this characteristic,it has been applied to the accurate measurement of physical quantities such as temperature,refractive index and small shift,and also has a wide range of applications in optical switches and sensors.It is found that the absorption and dispersion characteristics of the medium can be significantly changed by the atomic coherence effect,and then the beam shift of the system can be regulated.In this paper,the GH shift of the erbium-doped dielectric slab as well as the GH and IF shifts of the cavity coupled four-level atomic system are theoretically regulated based on the atomic coherence effect.1.The GH shifts of reflected and transmitted light when TE polarized light is incident on a erbium-doped dielectric slab are investigated.In this scheme,atomic coherence and quantum interference effects are used to change the absorption gain characteristics of the medium,and then the magnitude and direction of the GH shift are controlled.The results show that,when the system exhibits absorption characteristics,the GH shift of the reflected light is negative,and the shift increases with the decrease of absorption;when the system exhibits gain characteristics,the GH shift is positive,and the shift increases with the decrease of gain.It is obvious that the GH shift of the reflected beam is inversely correlated with the absorption gain coefficients of the medium.However,for the transmitted beam,the GH shift is positive regardless of the absorption or gain characteristics of the system,and the shift does not change with the change of absorption or gain.Further research finds that both the coherent driving field and the incoherent pumping field can be used to adjust the absorption gain of the system,and then to adjust the magnitude and direction of the GH shift in reflected light.Finally,it is found that with the increase of the thickness of the dielectric slab,the GH shift of the reflected light showed a periodic change.This scheme provides an effective method to control GH shift by adjusting external field parameters without changing the system structure.It is more convenient to operate in practical application,and the adjustment to the position of the reflected beam has potential application value in the optical switch.2.The GH and IF shifts of the reflected light were studied in a cavity-coupled four-level atomic system,and the shifts were adjusted by using the quantum interference effect to change the gain coefficient of the system.The results show that the shift of some light incident at a certain angle is obviously enhanced when the corresponding resonance conditions are satisfied.For TM polarized light,the GH shift is positive,and the positive shift increases significantly as the gain coefficient decreases.For TE-polarized light,the GH shift is positive at some resonance positions,and the shift increases obviously with the decrease of gain;however,for other resonance positions,as the gain increases,the GH shift changes from negative to positive value,realizing the change of shift direction.Further research finds that both the coherent driving field and the incoherent pumping field can adjust the gain coefficient of the system,and then regulate the magnitude and direction of the GH shift.At the same time,the IF shift of right-handed circularly polarized light is also studied.It is found that the IF shift is positive,and the shift gradually increases with the decrease of gain.Therefore,both the driving field and the pump field can also regulate the IF shift.In this scheme,the GH and IF shifts are enhanced without changing the structure of the system,and the magnitude and direction of GH shift are adjusted at some resonance positions,which has a certain application in beam regulation.