Ying Qiao Zhang

Polarization-independent electromagnetically induced transparency-like effects in stacked metamaterials based on Fabry–Pérot resonance

We propose a scheme for realizing plasmonic electromagnetically induced transparency (EIT)-like effects at optical frequencies in a stacked metamaterial that consists of two silver rings. The two silver rings are excited strongly by an incident wave. Based on Fabry–Perot (FP) resonance coupling between the two resonators, polarization-independent EIT-like effects appear at optical frequencies.

Ultra-narrow-band perfect absorber based on high-order plasmonic resonance in metamaterial

We demonstrate an, ultra-narrow-band perfect absorber based on high-order magnetic plasmonic resonance, which is polarization independent because of the ring element in the structure. When the thickness t of MgF2 is 60nm, the absorption at frequency 424.5THz is close to 1, its full width at half maximum (FWHM) is 13nm. In our structure, a wavelength sensitivity about 190nm/RIU is achieved by utilizing the absorption peaks alter upon the refractive index change. In addition, we also discuss the figure of merit (FOM*) under different reflective index of sample surface. Therefore, the ultra-narrow-band perfect absorber will provide the great potential applications to filters and plasmonic refractive index sensors.

Unidirectional reflectionless propagation in a non-ideal parity-time metasurface based on far field coupling

We propose a scheme to achieve a controllable unidirectional reflectionless propagation at exceptional point (EP) in a non-ideal parity-time metasurface consisting of two silver ring resonators. The unidirectional reflectionless propagation can be manipulated by simply adjusting the angle of incident wave and the distance s between two silver rings based on the far field coupling. In addition, the angle of incident wave in a wide range of ∼25° is available to achieve the unidirectional reflectionless propagation. Moreover, the unidirectional reflectionless propagation at EP is insensitive to the polarization of incident wave due to the two-ring structure.

Unidirectional Reflectionless Propagation in Plasmonic Waveguide System Based on Phase Coupling Between Two Stub Resonators

A scheme on unidirectional reflectionless propagation is theoretically investigated in a plasmonic waveguide system which consists of two metal–insulator–metal (MIM) stub resonators side coupled to an MIM plasmonic waveguide. By appropriately tuning the phase difference between two stub resonators, unidirectional reflectionless propagation at exceptional point, phase transition, and coherent perfect absorber are realized. Moreover, in both directions, reflectivity for one side is close to 0 and for the other side approximates to 0.8.

Narrow-dual-band perfect absorption plasmonic sensor in metamaterials based on the coupling of two resonators

We propose a narrow-dual-band metamaterial perfect absorber (MPA) made of metal-insulator-metal multilayer composite based on the coupling of two resonators. The absorptance of dual resonant peak all exceeding 95% at l1 = 270nm and 98% at l1 = 290nm (l1 is the length of ‘left’–‘right’ pair), respectively, where the full absorption width at half-maximum is about 3% (low frequency) and 5% (high frequency). The narrow distance of dual resonant peak is 31.4THz together with 43.6THz when l1 = 270nm and 290nm, respectively. In addition, we demonstrate that the MPA can work as a sensitive sensor for refractive index sensing. The figure of merit FOM* reaches 197.7 (low frequency) and 274.8 (high frequency) when l1 = 290nm. The narrow-dual-band peak position can be controlled by changing l1 as well.

Switching the unidirectional reflectionlessness by polarization in non-ideal PT metamaterial based on the phase coupling

An effective scheme on switching the exceptional point(EP) where unidirectional reflectionlessness occurs is firstly proposed in non-ideal PT metamaterial via the polarization of incident light. The unidirectional reflectionlessness could be effectively controlled only by adjusting the phase coupling of the two resonators which are consisted of two identical but vertically placed crosses and are excited by incident light as an effective gain. Besides, the unidirectional perfect absorber occurs in the vicinity of EP.

Dual-band unidirectional reflectionless phenomena in an ultracompact non-Hermitian plasmonic waveguide system based on near-field coupling

Dual-band unidirectional reflectionlessness and coherent perfect absorption (CPA) are demonstrated in a non-Hermitian plasmonic waveguide system based on near-field coupling between a single resonator and the resonant modes of two resonators showing an electromagnetically induced-transparency-like (EIT-like) effect. The non-Hermitian plasmonic system consists of three metal-insulator-metal (MIM) resonators coupled to a MIM plasmonic waveguide.

Unidirectional reflectionlessness and perfect nonreciprocal absorption in stacked asymmetric metamaterial based on near-field coupling

We propose a scheme for achieving unidirectional reflectionlessness and perfect nonreciprocal absorption at the exceptional point, based on near-field coupling in a stacked asymmetric nanostrip metamaterial structure. The result of theoretical analysis shows good agreement with a numerical simulation. Unidirectional reflectionlessness is realized well in wide ranges of the parameters s and a. The absorbance reaches ~1 in the +z incident direction, and the contrast ratio of the reflectance between the +z and −z incident directions is ~1.

Unidirectional reflectionless phenomena in a non-Hermitian quantum system of quantum dots coupled to a plasmonic waveguide

Unidirectional reflectionless phenomena are investigated theoretically in a non-Hermitian quantum system composed of several quantum dots and a plasmonic waveguide. By adjusting the phase shifts between quantum dots, single- and dual-band unidirectional reflectionlessnesses are realized at exceptional points based on two and three quantum dots coupled to a plasmonic waveguide, respectively. In addition, single- and dual-band unidirectional perfect absorptions with high quality factors are obtained at the vicinity of exceptional points.