We present three monolithic metamaterial-based THz bandpass filters, the skewed circular slot rings, meandered slots and Jerusalem cross slots, to fit in the THz gap. These THz bandpass filters are comprised of a metal-dielectric-metal (MDM) structure that supports multiple resonances of electric dipole, magnetic dipole, and standing-wave-like modes. By exciting and further hybridizing these individual resonance modes, we demonstrate excellent performance of broad bandwidth and sharp band-edge transition beyond conventional bandpass filters. By further employing our ad hoc Genetic Algorithm (GA) and Periodic Method of Moments (PMM) to optimize our designs, we achieve an ultra-broad 3dB fractional bandwidth and sharp band-edge transition up to 82.2% and 58.3 dB/octave, respectively, benefiting the practical applications such as material recognition in security systems, imaging, and absorbers.

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Abstract-By enabling both cavity modes and plasmonic resonance together in the designed two-handed metamaterial, we demonstrate a square-wave-like (SWL) bandpass filter with high-ratio bandwidth (HRB). Our results show that this metamaterial-based bandpass filter possesses high-ratio bandwidth of 30 GHz centered at 92 GHz, excellent transmittance beyond 87.5%, sharp transition within 1.0 GHz from −3 dB to −20 dB as upper and lower band edge transitions, and dualband behavior. Such an HRBSWL bandpass filter can be scalable and readily applicable for the commercialized unlicensed 60 GHz spectra with a bandwidth exceeding 7 GHz, solving the challenge of conventional passive bandpass filters to allow wide bandwidths and great quality factors simultaneously.

Electromagnetic components are important for ultraviolet (UV) applications. However, due to the limitation in the materials’ intrinsic responses, there are fewer electromagnetic components in high-frequency regimes than in low-frequency ones. Conventional UV components manipulate the wavefront via geometric phase accumulation; thus, they are significantly bulky and inefficient. In this study, we demonstrate all-dielectric Huygens’ metasurface (ADHMS) at a near-ultraviolet (NUV) regime. The NUV-ADHMS is comprised of resonant titanium dioxide (TiO2) nanodisks, with the ultrathin thickness of the fifth wavelength. In addition, by modulating the diameter of the resonant TiO2 nanodisks, we can simultaneously excite and control both electric and magnetic dipoles, achieving a powerful wavefront engineering of the near-unity transmittance and a full range of the 2π phase coverage. Finally, we employed the NUV-ADHMS to bend a normal incident beam, demonstrating a deflection angle of 11° at a wavelength of 405 nm.

Transformation optics has brought a wave of fanaticism among researchers to realize the first-ever invisible cloak over the past decade. Several relevant devices, including internal cloaks, external cloaks, and mantle cloaks, have already been proposed, with a few being experimentally demonstrated. Still, the proposed cloaks possess their insufficiencies to realize a reciprocal cloak. To better illustrate the cloak, here we report a new approach to a transformation-optics-based reciprocal cloak with designed dielectric-annulus-based metamaterials. Our results indicate we can easily control the anisotropic constitutive parameters at will. In addition, the as-fabricated cloak enables concurrent vision and movements of a hidden object, evidenced by both simulated and measured field distributions. More importantly, the cloak demands no bespoke design and is applicable to arbitrary electric-large objects. We affirm that we provide a method to developing the first-ever reciprocal cloak in experiments, and believe that the cloak could be further operated at visible ranges through the methodology we introduced, paving a route toward future applications in the fields of optics, physics, materials science, etc.