The Goos-Hänchen (GH) shift refers to a lateral displacement (from the path expected from geometrical optics) along an interface in totally internal reflection. This phenomenon results from a coherence effect. In order to bring to light the role of coherence, the reflection of partially coherent light fields was investigated within the framework of the theory of coherence. A formal expression for the GH shifts of partially coherent light fields is obtained in terms of Mercer's expansion. It is shown that both the spatial coherence and the beam width have an important effect on the GH shift, especially near the critical angles (such as totally reflection angle). These results are important to observe the GH shifts of the beams with imperfect coherence, like x-ray and matter-wave beams.
The Goos-Hänchen (GH) shift refers to a lateral displacement (from the path expected from geometrical optics) along an interface in totally internal reflection. This phenomenon results from a coherence effect. In order to bring to light the role of coherence, the reflection of partially coherent light fields was investigated within the framework of the theory of coherence. A formal expression for the GH shifts of partially coherent light fields is obtained in terms of Mercer's expansion. It is shown that both the spatial coherence and the beam width have an important effect on the GH shift, especially near the critical angles (such as totally reflection angle). These results are important to observe the GH shifts of the beams with imperfect coherence, like x-ray and matter-wave beams.
The negative and positive Goos-H\"anchen (GH) shifts in reflected light are revisited for a partial coherent light incident on a cavity. A three-level dilute gaseous atomic medium, which follows two-photon Raman transitions, is considered in a cavity. The anomalous (negative group index) and normal (positive group index) dispersions of the intracavity medium lead to negative and positive GH shifts, respectively. The effects of beam width, spatial coherence, and mode index of partial coherent light fields are studied on the negative and positive GH shifts. It is observed that the amplitude of negative and positive GH shifts are relatively large for a small range of beam width and for a small value of spatial coherence of partial coherent light beams. The amplitude of GH shifts becomes small for large beam width and spatial coherence of incident light. Further, the distortion in the reflected light field increases when the amplitude of the GH shifts increases and vice versa.
Goos–Hänchen (GH) shifts in the reflected and transmitted light are investigated for p-polarized partially coherent light beams incident on a cavity having a quantum dot (QD) system as the intracavity medium. The coherent coupling between the two quantum dots via a tunneling field leads to tunneling-induced transparency and giant Kerr nonlinearity with vanishing absorption. The Kerr nonlinearity of the double QD system thus increases the amplitude of GH shifts in the reflected and transmitted light. The influence of the spatial coherence and the beam width of the partially coherent light fields on GH shifts in the reflected and transmitted light are also investigated, and large GH shifts are reported for the small range of the spatial coherence and the beam width of the partially coherent light field.
The Goos-H\"anchen (GH) shift is a specifical optical phenomenon that describes a shift parallel to the reflected light inside the plane of incidence, when a finite-width light undergoes total internal reflection at the interface of medium. Although the GH shift in optics has been widely observed experimentally, its generalization remains uncovered completely in relativistic quantum mechanics for the spinor structure and the possible existence of Klein's paradox. Through approximation and angular spectrum analysis, we calculate the GH shift for Dirac fermions under relativistic conditions when they are incident obliquely on a three-dimensional infinite potential barrier. Furthermore, we find that the relativistic quantum GH shift will degenerate into the result based on Schr\"odinger equation under nonrelativistic limit, while the GH shift can be negative in Dirac's framework, which is different from the nonrelativistic case.
In conventional optics for light waves, the pioneering work by Goos-Hänchen in 1947 on the lateral shift (or displacement) of a light beam along the surface of a dielectric boundary under the condition of total reflection has stimulated a large number of studies. The key physics behind the Goos-Hänchen shift is the nature of wave interference. From the perspective of wave optics, the incident beam of a finite transverse width can be viewed as composed of plane wave components, each of which has a slightly different transverse wavevector. Each wave component, after the total internal reflection, undergoes a different phase shift, and the superposition of all the reflected wave components gives rise to the lateral shift of the intensity peak in the reflected beam.
In this work, we investigate the manipulation of the Goos-Hänchen (GH) shifts, referring to the lateral displacement of light beams at planar interfaces, in a global sodium atomic vapor medium by utilizing its tunable optical characteristics under the coherent control fields and the variable incident angles (0.6rad≤θ≤0.8rad). We achieve this by accurately manipulating probe detuning and control field intensities using a technique called 'electromagnetically induced transparency (EIT)'. EIT is a quantum interference effect that makes a medium transparent to a probe beam. By combining a near-resonant probe beam with transitions in the sodium atoms [D₂ line (5S1/2→5P3/2)], we obtain remarkable amplification of absorption, reflection, and transmission with spatially shifted beams that present up to ±4λ bidirectional GH shifts in reflection and ±2λ in transmission. The non-ideal normalization condition (∣T∣2+∣R∣2+∣A∣2<1) results from the redistribution of energy due to these shifts and indicates that established efficiency bounds no longer apply in coherent media. The GH-shifted beams astonishingly also maintain uniform intensity profiles at large displacements. Here, then, angular-dependent reflection pivots peak around critical angles, and transmission shifts are dynamically tunable, all emphasizing the atomic susceptibility gradients as key shapers for beam steering. These observations reveal unprecedented promise in applications, such as super-precision optical measurement, sub-wavelength displacement detection, and refractive index measurement, thus making sodium atomic vapors a tunable platform for advanced photonic devices with unique and high sensitivity. Keywords: Goos-Hänchen shift, Sodium atomic vapor, Atomic coherence, Beam displacement sensing, Optical susceptibility modulation
As a paraxial wave packet is reflected or refracted from a planar interface separating two material media, it experiences spatial and angular shifts of its center position with respect to predictions of the geometrical ray picture. These in-plane and out-of-plane beam shifts are known as Goos-Hänchen and Imbert-Fedorov shifts, respectively. We discover a universal link between the phase-space nonseparability of an incident wave packet of any degree of spatial coherence and the reflected beam shifts. We unveil coherence Goos-Hänchen and coherence Hall effects, absent in the fully coherent limit. While the former effect can trigger a pronounced enhancement of the spatial Goos-Hänchen shift, the latter enables control of the spatial Imbert-Fedorov shift, from complete cancellation at a certain incidence angle to dramatic enhancement of the shift to giant magnitudes for nearly incoherent incident wave packets. Our results are equally applicable to optical, x-ray, and neutron, as well as matter waves, and they showcase novel phenomena in wave-matter interactions.