We propose a terahertz (THz) vortex emitter that utilizes a high-resistance silicon resonator to generate vortex beams with various topological charges. Addressing the challenge of double circular polarization superposition resulting from the high refractive index contrast, we regulate the transverse spin state through a newly designed second-order grating partially etched on the waveguide’s top side. The reflected wave can be received directly by a linearly polarized antenna, simplifying the process. Benefiting from the tuning feature, a joint detection method involving positive and negative topological charges identifies and detects rotational Doppler effects amid robust micro-Doppler interference signals. This emitter can be used for the rotational velocity measurement of an on-axis spinning object, achieving an impressive maximum speed error rate of ∼2 % . This approach holds promise for the future development of THz vortex beam applications in radar target detection and countermeasure systems, given its low cost and potential for mass production.
The influence of the inner disk radius r, the filling ratio α, numbers of sectors N, and the gap g on transmission response for corrugated metallic disk (CMD) with single C-shaped resonator(CSR) has been fully studied. The results indicate that varying parameters r can efficiently excite the higher order spoof localized surface plasmon modes in corrugated metallic disk. The relationship between the bright dipole and dark multipolar resonances presents the possibility of high Q dark resonances excitation. All results may be of great interest for diverse applications.
A novel invisible media based on transformation optics consisting of three regions to investigate invisibility was proposed here. What the media does is to compress the light to a small region so that the light can avoid interacting with objects, and then it would be recovered in the latter. Comparing with the traditional cylinder cloak, which require the light propagating around the concealed region, the media would help us to avoid singularity of material parameters. Finite element simulations for two-dimensional cases have been performed to prove these ideas.
Based on transformation optics and complementary media (folded geometry), levitative carpet cloak and overlapping effects (anti-mirror effects) can be realized. In common case, the levitative carpet cloak is limited by the shape of the hidden object, and the early folded geometry method can just make two objects with different shapes appear as only one. Here, based on transformation optics and finite element simulations, we propose an anisotropic but homogeneous shifting media that can shift an arbitrary-shaped object from original place to another place in terahertz (THz) region. As a result, an arbitrary shaped object levitated on a flat perfect electric conductor ground and covered with the shifting media cannot be detected, leading to the levitative and shape-independent carpet cloak. Furthermore, optical overlapping effects such as making two separated objects with the same shape appear as only one, can be also realized by using this kind of shifting media.
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