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We present a theoretical investigation of the Goös-Hanchen shift (GHS) experienced by acoustic and optical vibrational modes reflected and transmitted from the surfaces of a semiconductor thin film sandwiched between two semi-infinite media. Our study focuses on the impact of the incident angle on the GHS, considering the coupling between longitudinal and transverse modes. For acoustic vibrations, our findings reveal that the GHS can reach magnitudes up to seven times larger than the thickness of the thin film and up to 20 times larger than the incident wavelength. Besides, it is shown that this significant amplification of the GHS highlights the strong influence of the incident angle and the frequency of the modes involved. In the case of optical vibrations, we observe even more pronounced GHS values, exceeding 30 times the incident wavelength. This demonstrates the potential of GHS in acoustical systems, which opens up possibilities for applications in the design of acoustic devices., (Creative Commons Attribution license.)

This investigation focuses on the Goos-Hänchen (GH) and Imbert-Fedorov (IF) shifts on the surface of the uniaxial hyperbolic material hexagonal boron nitride (hBN) based on the biaxial hyperbolic material alpha-molybdenum (α-MoO 3 ) trioxide structure, where the anisotropic axis of hBN is rotated by an angle with respect to the incident plane. The surface with the highest degree of anisotropy among the two crystals is selected in order to analyze and calculate the GH- and IF-shifts of the system, and obtain the complex beam-shift spectra. The addition of α-MoO 3 substrate significantly amplified the GH shift on the system's surface, as compared to silica substrate. With the p-polarization light incident, the GH shift can reach 381.76λ 0 at about 759.82 cm -1 , with the s-polarization light incident, the GH shift can reach 288.84λ 0 at about 906.88 cm -1 , and with the c-polarization light incident, the IF shift can reach 3.76λ 0 at about 751.94 cm -1 . The adjustment of the IF shift, both positive and negative, as well as its asymmetric nature, can be achieved by manipulating the left and right circular polarization light and torsion angle. The aforementioned intriguing phenomena offer novel insights for the advancement of sensor technology and optical encoder design.

The enhancement of the Goos-Hänchen (GH) shift has become a research hotspot due to its promoted application of the GH effect in various fields. However, currently, the maximum GH shift is located at the reflectance dip, making it difficult to detect GH shift signals in practical applications. This paper proposes a new metasurface to achieve reflection-type bound states in the continuum (BIC). The GH shift can be significantly enhanced by the quasi-BIC with a high quality factor. The maximum GH shift can reach more than 400 times the resonant wavelength, and the maximum GH shift is located exactly at the reflection peak with unity reflectance, which can be applied to detect the GH shift signal. Finally, the metasurface is used to detect the variation in the refractive index, and the sensitivity can reach 3.58 × 10 6 μm/RIU (refractive index unit) according to the simulation's calculations. The findings provide a theoretical basis to prepare a metasurface with high refractive index sensitivity, a large GH shift, and high reflection.

In this paper, we demonstrated the ability of a plasmonic metasensor to detect ultra-low refractive index changes (in the order of ∆n = 10 -10 RIU), using an innovative phase-change material, vanadium dioxide (VO 2 ), as the sensing layer. Different from current cumbersome plasmonic biosensing setups based on optical-phase-singularity measurement, our phase signal detection is based on the direct measurement of the phase-related lateral position shift (Goos-Hänchen) at the sensing interface. The high sensitivity (1.393 × 10 8 μm/RIU for ∆n = 10 -10 RIU), based on the Goos-Hänchen lateral shift of the reflected wave, becomes significant when the sensor is excited at resonance, due to the near-zero reflectivity dip, which corresponds to the absolute dark point (lower than 10 -6 ). GH shifts in the order of 2.997 × 10 3 μm were obtained using the optimal metasurface configuration. The surface plasmon resonance (SPR) curves (reflectivity, phase, GH) and electromagnetic simulations were derived using the MATLAB programming algorithm (by the transfer matrix method) and Comsol modeling (by finite element analysis), respectively. These results will provide a feasible way for the detection of cancer biomarkers.

In this letter, we demonstrate the existence of large transmitted optical positive and negative Goos-Hänchen shifts in photonic crystal slabs numerically and experimentally. The Goos-Hänchen shift we observed directly reaches ∼20 μm, which is 30 times the wavelength, approaching the radius of the beam waist. To explain this phenomenon, we measure the transmission phase through the phase measurement system and find there is an acute phase change near the resonance in photonic crystal slabs, which enhances the Goos-Hänchen shift. Our experimental results are consistent with simulation, and the work can be used to modulate the propagation of light in further research., (© 2022 the author(s), published by De Gruyter, Berlin/Boston.)

Goos-Hänchen shift provides a way to manipulate the transverse shift of an optical beam with sub-wavelength accuracy. Among various enhancement schemes, millimeter-scale shift at near-infrared range has been realized by a simple symmetrical metal-cladding waveguide structure owing to its unique ultrahigh-order modes. However, the interpretation of the shift depends crucially on its definition. This paper shows that the shift of a Gaussian beam is discrete if we follow the light peak based on the stationary phase approach, where the M-lines are fixed to specific directions and the beam profile is separated near resonance. On the contrary, continuous shift can be obtained if the waveguide is illuminated by a vortex beam, and the physical cause can be attributed to the position-dependent phase-match condition of the ultrahigh-order modes due to the spatial phase distribution.

A multilayer structure based on Dirac semimetals is investigated, where long-range surface plasmon resonance (LRSPR) of a dielectric layer/Dirac semimetal/dielectric layer are coupled with surface plasmon polaritons (SPPs) on graphene to substantially improve the Goos−Hänchen (GH) shift of Dirac semimetals in the mid-infrared band. This has important implications for the study of mid-infrared sensors. We studied the reflection coefficient and phase of this multilayer structure using a generalized transport matrix. We established that subtle changes in the refractive index of the sensing medium and the Fermi energy of the Dirac semimetal significantly affected the GH shift. Our numerical simulations show that the sensitivity of the coupling structure is more than 2.7×107 λ/RIU, which can be used as a potential new sensor application. The novelty of this work is the design of a tunable, highly sensitive, and simple structured mid-infrared sensor that takes advantage of the excellent properties of Dirac semimetals.

We demonstrate potential molecular monolayer detection using measurements of surface plasmon resonance (SPR) and angular Goos-Hänchen (GH) shift. Here, the molecular monolayer of interest is a benzenethiol self-assembled monolayer (BT-SAM) adsorbed on a gold (Au) substrate. Excitation of surface plasmons enhanced the GH shift which was dominated by angular GH shift because we focused the incident beam to a small beam waist making spatial GH shift negligible. For measurements in ambient, the presence of BT-SAM on a Au substrate induces hydrophobicity which decreases the likelihood of contamination on the surface allowing for molecular monolayer sensing. This is in contrast to the hydrophilic nature of a clean Au surface that is highly susceptible to contamination. Since our measurements were made in ambient, larger SPR angle than the expected value was measured due to the contamination in the Au substrate. In contrast, the SPR angle was smaller when BT-SAM coated the Au substrate due to the minimization of contaminants brought about by Au surface modification. Detection of the molecular monolayer acounts for the small change in the SPR angle from the expected value.

The change of the phase of light under the evolution of a nanomaterial with time is a promising new research direction. A phenomenon directly related to the sudden phase change of light is the Goos-Hänchen (G-H) shift, which describes the lateral beam displacement of the reflected light from the interface of two media when the angles of incidence are close to the total internal reflection angle or Brewster angle. Here, an innovative design of lithography-free nanophotonic cavities to realize electrically tunable G-H shifts at the singular phase of light in the visible wavelengths is reported. Reversible electrical tuning of phase and G-H shifts is experimentally demonstrated using a microheater integrated optical cavity consisting of a dielectric film on an absorbing substrate through a Joule heating mechanism. In particular, an enhanced G-H shift of 110 times of the operating wavelength at the Brewster angle of the thin-film cavity is reported. More importantly, electrically tunable G-H shifts are demonstrated by exploiting the significant tunable phase change that occurs at the Brewster angles, due to the small temperature-induced refractive index changes of the dielectric film. Realizing efficient electrically tunable G-H shifts with miniaturized heaters will extend the research scope of the G-H shift phenomenon and its applications., (© 2021 Wiley-VCH GmbH.)

Two-dimensional surface polaritons (2DSPs), such as graphene plasmons, exhibit various unusual properties, including electrical tunability and strong spatial confinement with high Q-factor, which can enable tunable photonic devices for deep subwavelength light manipulations. Reflection of plasmons at the graphene's edge plays a critical role in the manipulation of 2DSP and enables their direct visualization in near-field infrared microscopy. However, a quantitative understanding of the edge-reflections, including reflection phases and diffraction effects, has remained elusive. Here, we show theoretically and experimentally that edge-reflection of 2DSP exhibits unusual behaviors due to the presence of the evanescent waves, including an anomalous Goos-Hänchen phase shift as in total internal reflections and an unexpected even-odd peak amplitude oscillation from the wave diffraction at the edge. Our theory is not only valid for plasmons in graphene but also for other 2D polaritons, such as phonon polaritons in ultrathin boron nitride flakes and exciton polariton in two-dimensional semiconductors.