Large spatial shifts of reflected light beam off biaxial hyperbolic materials

Many optical systems that deal with polarization rely on the adaptability of controlling light reflection in the lithography-free nanostructure. In this study, we explore the Goos–H?nchen(GH) shift and Imbert–Fedorov(IF) shift in a biaxial hyperbolic film on a uniaxial hyperbolic substrate. This research statistically calculates and analyzes the GH shift and IF shift for the natural biaxial hyperbolic material(NBHM). We select the surface with the strongest anisotropy within the NBHM and obtain the complex beam-shift spectrum. By incorporating the NBHM film, the GH shift caused by a transversely magnetic incident-beam on the surface increases significantly compared with that on the uniaxial hyperbolic material. The maximum of GH shift can reach 86 λ0at about 841 cm-1when the thickness of NBHM is 90 nm, and the IF shift can approach 2.7 λ0for a circularly-polarized beam incident on a 1700-nm-thick NBHM. It is found that the spatialshift increases when a highly anisotropic hyperbolic polariton is excited in hyperbolic material, where the shift spectrum exhibits an oscillating behaviour accompanied with sharp shift peak(steep slope). This large spatial shift may provide an alternative strategy to develop novel sub-micrometric optical devices and biosensors.

Tunable enhanced spatial shifts of reflective beam on the surface of a twisted bilayer of hBN

We investigated Goos-Hänchen(GH)and Imbert-Fedorov(IF)shifts of a reflective beam on a twisted bilayer of hexagonal boron nitride(hBN),where a left circularly polarized beam was incident on the surface.Our results demonstrate that the twist angle between the two optical axes plays an important role in obtaining large shifts with a high reflectivity.The GH shift with 10λ_(0) is achieved,while the reflectivity is near 100%by tuning the twist angle.The maximum of the IF shift is found in the certain condition satisfied by the reflective coefficients,and the shift strongly depends on the twist angle between the optical axes of the two slabs.The spatial shifts obtained directly from the GH and IF shift definitions were provided,which indicate that the theoretical results from the stationary phase method are believable.These results may open up a new way for developing the nano-optical devices.

Narrowband perfect terahertz absorber based on polar-dielectrics metasurface

We theoretically propose a narrowband perfect absorber metasurface(PAMS) based on surface phonon polaritons in the terahertz range. The PAMS has unit cell consisting of a silver biarc on the top, a thin polar-dielectric in the middle and a silver layer at the bottom. The phonon polaritons are excited at the interface between the silver biarc and the polar dielectric, and enhance the absorption of the PAMS. The absorption peak is at 36.813 μm and the full width half maximum(FWHM) is nearly 36 nm, independent of the polarization and incidence angle. The electric fields are located at the split of the biarc silver layer and the quality factor Q is 1150. The FWHM decreases with the decreasing split width. When the thickness of the bottom layer is larger than 50 nm, the narrow band and high absorption are insensitive to the thickness of those layers. The designed absorber may have useful applications in terahertz spectra such as energy harvesting, thermal emitter, and sensing.

Nonlinear polaritons in antiferromagnetic/nonmagnetic superlattices

We discuss nonlinear characteristics of surface and bulk magnetic polaritons in the AF/NM superlattices composed of nonlinear antiferromagnetic and linear nonmagnetic layers.The results obtained for nonlinear bulk modes show the