We proposed a multilayer infrared metamaterial absorber with metal-insulator-metal (MIM) stacks and patterned nanostructured surfaces for ultra-broadband infrared applications. Chromium (Cr) and silicon dioxide (SiO2) were designated as the main materials of the absorber considering assessing the real functionalities of several metals and insulator materials in the structure. Furthermore, the electromagnetic field distribution shows that the stacks of different MIMs above the structure excite absorption peaks in distinct wavelength ranges, and the absorption range can be enlarged by manipulating structural parameters. The average absorptivity is higher than 80% throughout a wide wavelength range of 780 nm to 5500 nm, according to results of numerical simulation. The absorption spectrum encompasses the entire near-infrared and mid-infrared range, and it has promising applications in spectral sensing, infrared light sources, and detectors.
Fano resonance with high quality (Q) factor is of great significance to enhance the interaction between light and matter. The all-dielectric metasurface has low loss and can be used to realize the Fano resonance with high Q-factor. Herein , we propose a novel metasurface and apply it to the optical refractive index sensor in the near infrared. It consists of a silicon layer based on four rectangular holes and the substrate is silica. By introducing a new rectangular hole, the symmetry of the structure is broken and two new Fano resonance peaks are excited at the same time. The maximum Q-factor is 7709 (at 1304.4 nm). It can be applied to optical refractive index sensor with sensitivity of 296.7 nm/RIU and FOM of 1483.5.
An all-dielectric metasurface structure, composed of triple silicon strip arrayed on silica substrate, is proposed in this letter. Simulation results show that multiple Fano resonances arise in the transmission spectrum, performing high-quality (Q)- factor and nearly 100% modulation depth. The highest Q-factor of ~2000. In addition, the Cartesian multipole decomposition technique (CMDT) is adopted to verify the excitation mode of the Fano resonances. The sensing performances of the proposed structure are investigated as well, yielding the refractive index sensitivity (S) of ~ 350 nm/RIU and maximum figure of merit (FOM) of ~ 56.7 RIU-1 . It is believed that the designed structure can provide some inspirations for the applications in nonlinear optics, optical modulations, lasing and biochemical sensing.
We designed ab all-dielectric device based on permittivity-asymmetric rectangular holes, yielding multiple Fano resonances with high Q-factor in the near-infrared regime. there is a newly-generated sharp Fano peak with arising from the interference between sub-radiant modes and the electric and magnetic dipole resonance modes. Combining the multipole decomposition based on cartesian system and the field distribution, the resonance modes are analyzed to be toroidal dipole (TD) and magnetic dipole (MD). Furthermore, the dependence on materials and geometric parameters has been studied and the maximal quality (Q)-factor reaches 28503. This structure may be used for optical switching, nonlinear optical devices, and laser
Plasmon-Induced Transparency (PIT) is extended from the classical electromagnetically induced transparency (EIT), which has been a hotspot in recent years because of its potential applications in optical integrated devices. In this letter, multiple Plasmon-Induced Transparency (PIT) effects are achieved by periodically arranged rectangular resonators (RRs). The proposed structure is composed of metal-dielectric-mental (MDM) waveguide with a connected stub cavity and coupled RRs. Two RRs with the same parameters are placed vertically and seen as a periodic unit. New PITs arise one by one as new RRs are etched continually. The interesting phenomenon can be applied in optical devices.
Fano resonance with high Q-factor based on all-dielectric metasurface is of great significance for the design of optical refractive index sensor. Herein, we proposed an all-dielectric metasurface structure based on silicon, which is composed of two circular holes and one hexagonal hole. The substrate is silica. Two schemes are put forward to achieve asymmetry structure: changing the radius of a circular hole and changing the circular hole into an elliptical hole. Both schemes can generate quasi-BIC mode. The transmission spectrum is calculated by finite difference time domain (FDTD) simulation software, and the maximum Q-factor can exceed 24000. Finally, the extremely narrow linewidth of Fano resonance is utilized to design the optical refractive index sensors, yielding the sensitivity of 273nm / RIU and figure of merit (FOM) of 2730.
This paper mainly presents a nanoscale plasmonic structure, consisting of a waveguide with baffle, a semicircle connecting with four rectangular cavities, called tooth cavities. The whole evolution process of adding tooth cavity and adjusting parameters from the basic structure is also analyzed. Additionally, the position of the tooth cavity is independently adjustable, and the best sensing characteristic curve can be obtained by adjusting the positions of the middle two tooth cavities. Due to the coupling between the wide-spectrum resonance excited by the baffle in waveguide and narrow spectrum resonances emerging from the semicircular cavity connecting rectangular cavities, multi-Fano resonances arise in the simulation results. The transmission spectrum of the proposed structure indicates that 5 Fano peaks are generated in total, and the transmittance of the highest Fano peak can reach 0.88. The structure can be used as a refractive index sensor with a sensitivity of 1000 nm/RIU and figure of merit (FOM) of 38026 by avail of Fano resonance.
In this paper, a novel plasmonic structure consisting of a metal-insulator-metal (MIM) waveguide which is separated in intermediate region coupled with a cross-shaped cavity (CSC) is proposed. Based on the finite element method (FEM), results are simulated by COMSOL Multiphysics software concluding three different Fano resonances peaks and an independent Lorentz peak. Theoretically, multimode interference coupled mode theory (MICMT) is used to calculated the formation of the peaks. Besides, by changing the parameters of the structure, the influence of different parameters on each resonance peak is studied. Based on the original CSC structure, the system is extended to five types of Fano resonance system by appending a semi annular (SA) structure. The research results show that the sensitivity of expanded structure can be up to 1478 nm/RIU, and the FOM value can be as high as 5×105, demonstrating its excellent nano-sensing performance and can be used as an efficient refractive index (RI) sensor.
A plasmonic structure, constituted by metal insulator metal waveguides and split annular cavity connected with rectangular resonator (SACRR), is proposed and investigated. Numerical simulation by the finite element method (FEM) has been done to investigate the transmittance properties of the proposed structure and four Fano resonances arise in the results. To analyze and verify the simulation results, multimode interference coupled mode theory is engaged, theoretically. In addition, the structural parameters are analyzed and discussed to design and control the proposed structure, which shows sufficient flexibility. Due to multi-Fano resonances providing multiple monitoring points and the extremely sharp asymmetry of Fano resonance, the structure can service as a high-performance multichannel refractive index nanosensor with a sensitivity of 1000 nm/RIU and maximum figure of merit of 1.358 × 105. The designed structure can surely meet extensive applications for nanoscale devices and integrated optical devices.
Fano resonances based on circle-with-inner-core and stub structure are investigated using data derived from the finite element method and theoretically explained by the multimode interference coupled mode theory and the electric distribution in the system. The parameters of specific structure are modified to investigate the influence of different parts for this metal–insulator–metal system. Due to the high sensitivity to filled dielectric materials, the proposed structure can be applied as a refractive index sensor, whose performances are also explored. High sensitivity is gained as high as 1183.3 nm / RIU. And the figure of merit, a key parameter to describe the sensing characteristic, is achieved as 5.1115 × 104, which is better than most similar structures. Our work is significant for the sensitive refractive index nanosensor.
In this paper, a surface plasmon waveguide structure consisting of annular gap and metal-insulator-metal waveguides is proposed, and its spectral characteristics are analyzed and studied. The results show that this waveguide structure has good performance in narrowband filtering in sub-wavelength band, and the central wavelength of the transmission peak is linearly related to the angle of the annular with notch. The results are of great significance for the application of filtering structures in highly integrated photonic circuits.
A compact tunable quintuple Fano-like plasmonics structure, composed of a metal-insulator-metal, a baffle, a quarter ring and a rectangular cavity, was proposed and applied to refractive index sensor in this paper. According to the numerical simulations, quintuple Fano resonances, which derived from the coupling and interference between the narrow discrete state supported by the quarter ring and the rectangular cavity and the broad continuum state excited by the baffle, were obtained in its transmission spectrum. Additionally, the quintuple Fano resonances obtained can be easily tuned by changing the geometric parameters of the resonators. Because of the sharp asymmetry of Fano resonance, the proposed system can be served as a high efficient refractive index sensor with a sensitivity of 1600 nm/RIU and figure of merit (FOM) of 6743. Considering the development of high integrated photonic circuits, it is believed that the proposed structure can find significant applications in optical sensing and optical communication areas.
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