Magneto-optical Goos-Hänchen effect in a prism-waveguide coupling structure

Non-specular reflection of a narrow spatially phase-modulated Gaussian beam

The lateral and angular Goos-Hänchen shifts undergone upon reflection on a dielectric plate by a spatially phase-modulated Gaussian beam are derived. It is shown that the amplitude and direction of both lateral and angular shifts are very sensitive to the degree of spatial phase modulation of the incident beam, so that such modulation thus provides a means to control those shifts. It is also shown that the modulation incurs some beam reshaping upon reflection. Analytical calculations of the lateral shift are found to be in good agreement with numerical simulations of beam propagation before and after reflection. In these simulations, the required spatial transverse phase modulation is achieved by focusing a microwave Gaussian beam onto the dielectric plate with a non-spherical lens or a flat-surfaced thin lamella exhibiting a suitable gradient of its refractive index. The optimal parameters governing the spatial phase modulation are discussed to achieve: (i) enhancement of the lateral shift of a spatially phase-modulated beam in comparison to that of a non-modulated beam and (ii) simultaneous large values of reflectivity and of the lateral shift, while keeping the reshaping of the reflected beam to a minimum.

Weak measurement of magneto-optical Goos-Hänchen effect

As a lateral shift of reflected light beam from the optical interface, the Goos-Hänchen (GH) effect led to various practical applications in biosensing and optical field manipulations. Magneto-optical (MO) effect of dielectric or metal may bring flexible modulation for GH effect, which can be regarded as the magneto-optical Goos-Hänchen (MOGH) effect. In this paper, the GH and MOGH effects in a BK7 prism/Fe/Au waveguide enhanced by surface plasmon resonance (SPR) are demonstrated experimentally for the first time. By weak measurement, the GH and MOGH shifts are further amplified to facilitate their applications. By contrast, the results of theory and experiment are basically consistent. The maximum MOGH shift of the proposed BK7/Fe/Au waveguide achieves 120 μm when optimum thicknesses are chosen. As MOGH effect exhibits a higher sensitivity to the refractive index of sample than GH shift, it can be applied in refractive index detection. The demonstrated MOGH effect with advantages of high sensitivity and convenient control opens avenues for future applications with biosensors and functionally optical devices.

Surface plasmons excited by multiple layer grating

The surface plasmons that are excited by the multiple layer grating structures on the gold thin film are studied using the finite-difference time-domain method in this paper. The structure parameters' effects on the coupling enhancement of surface plasmons are examined, and the structure design guidelines are given. It is found that the distance between the grating layers and the distance between the gratings and gold thin film are the key structure parameters for better cavity resonances. To have the stronger field enhancements of the excited surface plasmons for the multilayer grating structures, it is found that the width of the gratings should be smaller for the lower grating layers. The multiple layer gratings with proper structure designs can have better performances than single layer grating structure because the cavity effects can enhance the light coupling and more light can be coupled into the surface plasmons by more layers of grating. It is found that the maximum electric field intensity for five layer grating structures can be 163% of the case of the single layer grating structure in our simulations.

Collinear heterodyne interferometer technique for measuring Goos-Hänchen shift

Directly measuring the difference of the lateral Goos-Hänchen shift between TM and TE polarized lights under total internal reflection using what we believe is a new approach is introduced. This approach is based on the heterodyne interferometer system with two acousto-optic modulators driven at different frequencies combined with an analyzer with a high extinction ratio, two polarization beam splitters, an isosceles glass prism with two base angles of a critical angle, and a position-sensitive detector with high resolution. This approach compared to a 45° right-angle prism used to obtain the Goos-Hänchen shift on the total internal reflection has the advantages of reducing angle-modulated noise caused by small angle error of a rotary stage, the measurement of the absolute GH shifts of TE or TM polarized light, respectively, by means of the aluminum coating deposited on parallel plate glass, and the potential to simultaneously measure the phase changes and the GH shift at surface plasmon resonance in a Kretschmann-Raether configuration.

Magnetic control of Goos-Hänchen shifts in a yttrium-iron-garnet film

We investigate the Goos-Hänchen (GH) shifts reflected and transmitted by a yttrium-iron-garnet (YIG) film for both normal and oblique incidence. It is found that the nonreciprocity effect of the MO material does not only result in a nonvanishing reflected shift at normal incidence, but also leads to a slab-thickness-independent term which breaks the symmetry between the reflected and transmitted shifts at oblique incidence. The asymptotic behaviors of the normal-incidence reflected shift are obtained in the vicinity of two characteristic frequencies corresponding to a minimum reflectivity and a total reflection, respectively. Moreover, the coexistence of two types of negative-reflected-shift (NRS) at oblique incidence is discussed. We show that the reversal of the shifts from positive to negative values can be realized by tuning the magnitude of applied magnetic field, the frequency of incident wave and the slab thickness as well as the incident angle. In addition, we further investigate two special cases for practical purposes: the reflected shift with a total reflection and the transmitted shift with a total transmission. Numerical simulations are also performed to verify our analytical results.