Spatial Imbert-Fedorov Shifts Research Articles

Spin-orbit interaction of light: When twisted light meets twisted metasurfaces

Singular optics and metamaterials are both fascinating branches of modern optics. While the twist of vortex beams in phase and polarization leads to singularities, the twist of metasurfaces also leads to extraordinary properties in both optics and electronics. Here we present the spin-orbit interaction of a vortex beam reflected on twisted few-layer hyperbolic metasurfaces. As a result, the spatial Imbert-Fedorov (IF) shift and photonic spin Hall effect (PSHE) shift are investigated. We find that the spatial IF shift versus twist angle is symmetrical about the $l=0$ shift and it is symmetrical about the origin for opposite twist angle with opposite topological charge. In addition, the PSHE shift versus twist angle is also symmetrical about the $l=0$ shift. The shifts are enhanced with increasing topological charge and show a pretty different dependence on the twist angle when the incident beam is in different polarization state. These findings provide a different perspective for further investigations of twisted light and twisted metasurfaces.

Ionosphere induced spatial Imbert Fedorov shifts

The reflection and transmission of radio waves are two most common techniques used to study the ionosphere. Considering an electromagnetic wave with a finite diameter, however, displacements and deflections different from the predictions of geometric optics arise. In this paper, we investigate thru calculations one type of these shifts, the out-of-plane Imbert-Fedorov (IF) displacements, induced by the ionosphere on the reflected radio waves. We model the ionosphere as a simple collection of electrons moving in a uniform magnetic field and use the resulting dispersive expressions to calculate the corresponding IF shifts. Since the ionosphere is a dispersive medium, we consider three cases: (1) metallic, (2) dielectric and (3) epsilon-near-zero (ENZ) behavior of the layer. We determine that there exists non-zero differential spatial IF shifts for all the three cases and find that the maximum shift of up to 95 m occurs when the ionosphere acts like an ENZ medium. Finally, we show that these transverse shifts are measurable and discuss how these can be utilized as a potential tool to profile the ionosphere using reflected radio waves.

Investigating Imbert–Fedorov shift at a planner interface of dispersive–dissipative dielectric–magnetic metamaterial

The main objective of this paper is to analyze the spatial Imbert-Fedorov shift (IFS) on a planar interface of dispersive-dissipative dielectric-magnetic metamaterial. Spatial IFS is calculated by utilizing the energy flux method. The Lorentz–Drude Model is used to calculate the complex permittivity and permeability of frequency-dependent material. The behavior of spatial IFS is examined in both lossy and lossless mediums of transmission. Furthermore, spatial IFS is analyzed by varying the losses of dispersive–dissipative dielectric–magnetic metamaterial. The impact of the resonance frequency is also observed in this manuscript. DPS metamaterial behaves like an ordinary material and highest positive IFS with value of 33λ is observed for lossless case. ENG and MNG metamaterials behave like the metal and negative shifts are observed with the order of −0.014λ and −2λ respectively for lossy case. Because of the backward travelling wave, the DNG metamaterial has a negative shift. IFS observed for Lossless DNG metamaterial is −15λ, which is larger than the ENG and MNG metamaterials.

Enhanced and tunable Imbert-Fedorov shift based on epsilon-near-zero response of Weyl semimetal

We theoretically investigate the reflected spatial Imbert–Fedorov (IF) shift of transverse-electric (TE)-polarized beam illuminating on a bulk Weyl semimetal (WSM). The spatial IF shift is enhanced significantly at two different frequencies close to the epsilon-near-zero (ENZ) frequency, where large values of reflection coefficients |r pp|/|r ss| are obtained due to the ENZ response induced different rapid increasing trends of |r pp| and |r ss|. Particularly, the tunable ENZ effect with tilt degree of Weyl cones and Fermi energy enables the enhanced spatial IF shift at different frequencies. The enhanced spatial IF shift also shows the adjustability of WSM thickness, incident angle and Weyl node separation. Our findings provide easy and available methods to enlarge and adjust the reflected IF shift of TE-polarized light with a WSM.

Determination of tilt degree and Weyl-node separation by the spatial Imbert-Fedorov shift near the Brewster angle

The Imbert-Fedorov (IF) shift at the optical interface of Weyl semimetal (WSM) is extremely significant to recognize the optical characteristics of WSM. In this paper, we have studied the spatial IF shift on the surface of a bulk WSM by theoretically deriving a 4 \ifmmode\times\else\texttimes\fi{} 4 magneto-optic matrix. It is found that the phenomenon of spatial IF shift changing from positive to negative occurs at an incident angle near the Brewster angle. Remarkably, this special phenomenon can be regulated by changing the frequency of incident light, tilt degree, and Weyl node separation. Specially, for a fixed Weyl node separation, the phenomena of spatial IF shift changing from positive to negative can be realized at different tilt degrees by simply changing the frequency, and there exists one-to-one correspondence between the tilt degree and frequency at these situations. Similarly, for a fixed tilt degree, these phenomena can be achieved at different Weyl node separations by changing the frequency, and there also exists one-to-one correspondence between the Weyl node separation and frequency. Therefore, these tunable phenomena of spatial IF shift changing from positive to negative enable the feasibility of accurate determination of tilt degree and Weyl node separation. Our study can also provide a reference for the research of IF shift in such similar structures.

Topological Imbert–Fedorov shifts in silicene

In this paper, we study the topological Imbert–Fedorov (IF) shifts of a light beam reflected from a silicene–substrate system in the presence of an externally applied electric field and circularly polarized beam. Silicene is a topological material and due to the strong spin–orbit interaction has a rich phase diagram. Using the famous Kubo formalism, we derive analytical expressions for the longitudinal and transverse Hall conductivities of silicene. By employing angular spectrum analysis, the analytical expression of the spatial IF shift is obtained. We show that electric field/circularly polarized light beam modulated positive and negative spatial beam shifts can be obtained by tuning the angle of incidence near the Brewster angle and the incident photonic energy in the terahertz regime. Furthermore, we also investigate the IF shifts in different topological phases of the silicene by driving the system through distinct topological quantum phase transitions (TQPTs), i.e., from topologically nontrivial to a semi-metallic state and further to a band insulating state by manipulating the interplay between the electric field and circularly polarized light beam. We believe these results are helpful for developing novel optoelectronic, spintronic, and valleytronic devices and may provide a possible technique for probing Berry curvature, topological Chern numbers, and TQPTs by direct optical measurement.

Adjustable spin Hall effect of light in surface plasmon resonance structure with consideration of angular Imbert–Fedorov shift

For a horizontally polarized Gaussian beam incident on surface plasmon resonance structure composed of prism, silver film, and absorptive liquid, the left- and right-handed circularly polarized components of the reflected beam undergo spin-dependent spatial and angular Imbert–Fedorov (IF) shift. We investigate spin Hall effect of light (SHEL) after the reflected beam travels a distance of Rayleigh range. It is shown that the maximum total transverse shift (TTS) of one spin component at Rayleigh range is always larger than the maximum spatial IF shift, and TTS is more sensitive to variations in the parameters of the structure than spatial IF shift. Furthermore, this SHEL is adjustable by changing the complex refractive index of the absorptive liquid. This research provides a simple way to enhance SHEL and may have potential application of improving the accuracy of sensors based on SHEL.

Photonic spin Hall effect in guided-wave resonance structure with consideration of beam propagation

We present a unified formalism about spatial and angular Goos-Hänchen (GH) and Imbert-Fedorov (IF) shifts. When a horizontally polarized Gaussian beam is reflected from guided-wave resonance structure, the photonic spin Hall effect (PSHE) caused by both spatial and angular IF shifts is theoretically investigated with consideration of beam propagation. When PSHE is observed at Rayleigh range of the reflected beam, the maximum total IF shift is larger than the maximum spatial IF shift. Meanwhile, total IF shift varies faster with the incident angle than the spatial IF shift. The formalism also shows that the spatial and angular IF shifts increase with the increase of the width of the resonant absorption dip. Theoretical predictions agree well with numerical calculations. Those results provide a new way to improve PSHE and have potential application of improving the accuracy of sensors based on PSHE of this structure.

Spatial Goos-Hänchen and Imbert-Fedorov shifts of rotational 2-D finite energy Airy beams

Expressions of Goos-Hänchen and Imbert-Fedorov shifts of rotational 2-D finite energy Airy beams are introduced in this paper. The influences of the second-order terms of the reflection coefficient on the spatial Goos-Hänchen shift (GHS) and spatial Imbert-Fedorov shift (IFS) of rotational 2-D finite energy Airy beams are theoretically and numerically investigated at the surface between air and weakly absorbing medium for the first time. It is found that the axial symmetry of the initial field of beams has huge influences on GHS and IFS and both of the GHS and IFS can be controlled by adjusting the rotation angle of the initial field distribution.

Enhanced Goos-Hanchen Shift and Imbert-Fedorov Shift in Three layered Kretschmann-Geometry with Gaussian Beam, Laguerre-Gaussian Beam and Bessel Beam in Silver Nano Layer with Surface Plasmon Resonance

A new theoretical approach towards the exact identification of the output reflected beam position by the effect of spatial Goos-Hanchen (GH) shift and Imbert-Fedorov (IF) shift using Gaussian beam, Laguerre-Gaussian beam and Bessel beam are observed, designed and simulated with the three layered Kretschmann geometry at a free space wavelength of 1550 nm, where the proposed configuration comprising a BK7 prism (n=1.5007) and a 50 nm thin metal layer of silver (n= 0.4096+10.048i). To the best of our knowledge several articles have been discussed, separately considering the Gaussian beam, Laguerre-Gaussian beam and Bessel beam in which without the composite effect of spatial GH shift and IF shift whereas the exact beam position can only be identified with the effect of these shifts. In our proposed configuration by varying incident angle through Bessel beam, the observed spatial GH shift is tuned from 44.267 µm to 0.261 µm and the spatial IF shift is tuned from 39.301 µm to -13.024 µm. With the same variation of incident angle, the spatial GH shift and IF shift are also observed for Gaussian beam and as well as for Laguerre Gaussian beam. This new idea explores the accurate tuning of output beam position with varying incident angle which expedites the path of fine tuning in optical switching within µm ranges.