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Controlling terahertz (THz) waves, especially the polarization state and deflection angle, is important in THz application systems. But most of conventional THz metasurfaces have limitations in efficiency and working bandwidth. Although Pancharatnam-Berry (P-B) metasurfaces shows excellent manipulation for the circular polarized (CP) waves (or called photonic spin states) without phase dispersion, there is still challenge in active controlling. Here, we developed a magnetically tunable gyrotropic P-B metasurface by combining the gyroelectric semiconductor InSb and the P-B elements, which obtain two important effects: One is the active photonic spin Hall effect, which controls the conversion between two CP states and the deflection in space. A broadband working frequency of 1.02∼1.7 THz is obtained with the sweeping deflection angle from 36.6° to 83.5° and the highest efficiency of over 70%. The other is photonic spin filter effect, which reflects one CP state but absorb the other orthogonal CP state, realizing nonreciprocal absorption with the isolation of 24 dB. This active, high efficiency and broadband P-B metasurface opens a new way in manipulation of the THz wave propagation and polarization states in both space and frequency domains. [ABSTRACT FROM AUTHOR]

Recent research work on magneto-optical micro- structure devices in terahertz (THz) regime has been reviewed. Some magneto-optical materials responding at THz frequency range were introduced. Based on these magneto-optical materials, MO microstructures devices were reviewed, including magnetic photonic crystals, magneto-plasmonics, and magneto-metasurface all in the submillimetre scale. These devices can realize several functions of isolating, modulation, sensing, and directional beam scanning. Moreover, the necessary conditions of forming THz nonreciprocal transmission in magneto-optical microstructure devices were concluded, and the tunability of these devices was also analysed, which strongly depends on the magneto-optical property of material and the symmetry of structure. The unique magneto-optical effects make it play an irreplaceable role in the high performance THz applications of communication, imaging, and sensing systems. [ABSTRACT FROM PUBLISHER]

An extraordinary optical transmission effect in a complementary metallic disk and hole array has been experimentally and numerically investigated in the terahertz (THz) regime, which shows a high transmission peak despite having zero effective aperture in the direction of light propagation. The results confirm that this effect is contributed not only by the surface plasmon excited on metallic disk and hole but also the resonance in the dielectric rod between them. Moreover, an optically pumped THz wave modulation with 40% amplitude modulation depth has been demonstrated in this device using a 532-nm laser with only 150 mW/mm2 power density. This novel plasmonic structure with high $Q$ transmission peak shows great promising applications in the THz modulation, filtering, and sensing. [ABSTRACT FROM PUBLISHER]

Terahertz (THz) silicon photonic column (PC) array has been designed and fabricated, and its resonance effect has been experimentally and numerically investigated. Using this resonance effect, the refractive index sensing for liquids has been demonstrated in this device by the theoretical model calculation, numerical simulation, and experimental measurement. Moreover, resonance dependence on different incident angles in this device has also been shown. These results confirm that this THz PC array can be used as a THz refractive index sensor with high sensitivity and robustness. This sensing strategy shows that the structured surface of this device is compatible for liquid monitoring and easy to couple and transmit THz waves, and therefore can be more easily implemented in liquid refractive index sensing. [ABSTRACT FROM PUBLISHER]

We have proposed and analyzed a novel terahertz (THz) single-polarization single-mode (SPSM) hollow-core fiber based on the index-matching coupling method. However, its coupling principle is different from the solid-core SPSM fiber. The confinement loss of the index-matched polarization state is increased slightly, while that of the other polarization state is enhanced by nearly two orders of magnitude. In particular, the confinement loss of the index-matched polarization state is only 0.004 dB/m at f=1.675~THz. [ABSTRACT FROM PUBLISHER]