Multiple Fano Resonances Research Articles

Low-frequency broadband acoustic ventilation meta-barrier based on consecutive multiple Fano resonances

Acoustic metamaterials utilizing Fano resonance provide the possibility of simultaneous airborne sound insulation and high-performance ventilation. However, the ultra-sharp line shape results in a narrow working frequency range, which is still insufficient for practical applications. In this work, we propose a low-frequency acoustic meta-barrier supporting consecutive multiple Fano resonances (CMFRs) with broadband (~75%) capability, efficient ventilation, and ultra-thin thickness, etc. The barrier features a binary metastructure, incorporating a chiral space coiling tunnel and a hollow pipe in a planar arrangement. This configuration offers discrete and continuous states within the composed Fano system, corresponding to the tunnel and the pipe, respectively. By means of superposition of multi-order Fano resonance modes, the destructive interference between the discrete and continuum states keeps effective in a broad frequency range, while simultaneously achieving high air permeability. Numerical results of transmission loss show significant attenuation of incident energy in the range of 479-1032 Hz. Our work lays the groundwork for next generation of Fano-based metamaterial applications, with far-reaching implications for noise control and related fields.

Multiple Fano Resonance Modes based Plasmonic Refractive Index Sensor for Edible Oil Adulteration Detection

Surface plasmon polariton (SPP)-based plasmonic sensors are increasingly replacing traditional bulky sensors in refractive index sensing, biosensing, food adulteration detection, and other applications due to their unique optical features and different Metal-Insulator-Metal (MIM) topologies. The present research introduces a new design for a highly sensitive MIM waveguide-based refractive index sensor. This design incorporates an innovative combination of an inverted U-shaped rectangular split-ring resonator (RSRR), a semi-circle-split-ring resonator (SCSRR), and a stub. The sensor’s wave-guiding capabilities, such as electromagnetic wave transmission, field profile distribution, and sensitivity, are meticulously analyzed using a two-dimensional finite-element method. The key objective of this device is to identify slight differences in the refractive index by observing shifts in resonant wavelength through the light’s interaction with the plasmonic structure. Moreover, optimizing the geometric parameters significantly enhances the sensor’s performance. The optimized sensor achieves a maximum refractive index sensitivity of 2400 nm/RIU, a figure of merit (FOM) of 45.28, and a Q-factor of 39.86, as demonstrated by simulation results. Further investigations reveal the MIM structure’s capacity to detect adulteration in edible oils, underscoring the sensor’s adaptability and its potential for widespread biosensing applications.

Multiple Fano Resonances Enabled by the Interference between an Out‐of‐Plane Plasmon Mode and Fabry–Pérot Cavity Modes

AbstractMultiple Fano resonances (mFRs) are arising as a promising optical platform to achieve precise sensing and detection. However, experimentally achieving mFRs by simple structures has remained challenging, which impedes the widespread applications of mFRs. Herein a simple structure composed of a single colloidal metal nanoparticle and a transition metal dichalcogenide flake to simultaneously achieve up to 8 FRs in experiments is demonstrated. Combining theoretical and experimental techniques, that an out‐of‐plane plasmon mode of the metal nanoparticle interferes with the Fabry–Pérot cavity modes from the WS2 flake to form mFRs in the visible region is proved. The simplicity and generality of the method further allow us to systematically study the tunability of the mFRs, in terms of the peak/dip positions and the number of FRs, by changing the structural parameters, which include the thickness of the WS2 flake, size and shape of the plasmonic nanoparticle. In addition, the quality of the mFRs is proved to be adjustable by tuning the reflectivity of the substrate in the system. The highest quality factor and spectral contrast of the achieved resonances are up to ≈180 and ≈0.95, respectively. The simple structure and high‐quality optical modes will prosper applications in precise sensing and light modulation.

Multiple toroidal dipole Fano resonances from quasi-bound states in the continuum in an all-dielectric metasurface

In this paper, a highly sensitive sensor consisting of a silicon nanorod and symmetric rings (SNSR) is presented. Theoretically, three Fano resonances with high Q-factors are excited in the near-infrared range by breaking the symmetry structure based on quasi-bound states in the continuum (Q-BICs). The electromagnetic near-field analysis confirms that the resonances are mainly controlled by toroidal dipole (TD) resonance. The structure is optimized by adjusting different geometrical parameters, and the maximum Q-factor of the Fano resonances can reach 7427. To evaluate the sensing performance of the structure, the sensitivity and the figure of merit (FOM) are calculated by adjusting the environmental refractive index: the maximum sensitivity of 474 nm/RIU and the maximum FOM of 3306 RIU-1. The SNSR can be fabricated by semiconductor-compatible processes, which is experimentally evaluated for changes in transmission spectra at different solution concentrations. The results show that the sensitivity and the Q-factor of the designed metasurface can reach 295 nm/RIU and 850, while the FOM can reach 235 RIU-1. Therefore, the metasurface of SNSR is characterized by high sensitivity and multi-wavelength sensing, which are current research hotspots in the field of optics and can be applied to biomedical sensing and multi-target detection.

Broadband ventilated sound insulation based on acoustic consecutive multiple Fano resonances

Broadband ventilated sound insulation based on acoustic consecutive multiple Fano resonances

Multiple Fano resonances by MIM waveguide coupling whispering gallery mode resonator and application in Refractive index sensing

In this study, a baffled metal–insulator–metal (MIM) waveguide coupled with a whispering gallery mode resonator (WGMR) is proposed. This structure could excite quadruple Fano resonances. The asymmetric Fano resonance transmittance spectrum and the electric field at the resonance peak were numerically simulated using the finite difference time domain method. The obtained data were fitted using the multimode interference coupled mode theory. The number of Fano resonance peaks was tuned by the outer radius of the WGMR. With other geometric parameters unchanged, the number of Fano resonance peaks increased with increasing outer radius of the WGMR. Thus, it achieved multiple Fano resonances by adjusting solely the radius of the WGMR. When the ring width was fixed, the structure could excite multiple Fano resonances within a certain outer radius range. This structure was used for refractive index sensing and its sensitivity and figure of merit (FOM) were 3004 nm/RIU and 3.14 × 104 in a gas environment, respectively. Therefore, the proposed structure can excite multiple Fano resonances and achieve high sensitivity and FOM, providing a theoretical basis for micro and nano applications.

Numerical investigation of a plasma-dielectric-plasma waveguide with tunable Fano resonances

Resonance and interference phenomena in waveguide systems are remarkable for control of electromagnetic wave propagations, with extensive applications in many areas. This paper introduces a plasma-dielectric-plasma (PDP) waveguide supporting multiple Fano resonances, made of a tooth cavity directly connected to a straight waveguide and a rectangle cavity with plasma holes. Different from metal-insulator-metal (MIM) waveguides at the near-infrared band with nanoscales, the PDP works in the microwave regime and with centimetre dimension. Furthermore, it has a prominent advantage in tunability due to inherent properties of gaseous discharge plasmas. A finite element method is adopted to study transmission responses and field distributions in details. Also, coupled mode and standing wave theories are applied to confirm the validity of numerical results and theoretically analyze Fano spectra, respectively. Results indicate that the number and position of Fano resonances can be modulated by adjusting the number of plasma holes and altering the plasma frequency, respectively. Also, the independent tunability of multiple Fano resonances can be verified by the additional structure. The numerical simulations provide a reference for plasma to modulate electromagnetic waves and may open up a new path for developing tunable microwave devices, especially in the parallel processing of microwave signals.

Nanometer refractive index sensor based on water droplet cavity structure with rectangular short rod

In this paper, a novel nano sensor structure is proposed, which consists of a metal-insulator-metal waveguide (MIM) with rectangular baffles and a water droplet cavity with rectangular stubs (WDCRS). The WDCRS structure optimizes the sensitivity of a single water droplet cavity and makes the transmission curve clearer and smoother. The transmission characteristics of WDCRS structure were simulated using finite element method (FEM). The transmission characteristics of the exported structure were analyzed in detail. In addition, the influence of structural geometric parameters on sensing performance was also studied, and it was found that the size of the water droplet cavity is a key factor in improving sensitivity. When applied to a refractive index sensor, the structure achieves a sensitivity of up to 2,300 nm/RIU with a corresponding figure of merit (FOM) of 60.5. These works provide some ideas for the design of high-performance nanostructures and multiple Fano resonance excitation structures.

Multiple fano resonances based on all-dielectric metastructure for refractive index sensing

We investigate an optical refractive index sensor based on an all-dielectric metastructure in the near-infrared regime for achieving high sensitivity and high quality factor (Q-factor). By introducing the asymmetry in the metastructure, four sharp Fano resonances with high Q-factor are generated owing to the transition from symmetry-protected bound states in the continuum (BIC) to quasi-BIC, and the magnetic quadrupole (MQ) resonance, magnetic dipole (MD) resonance, and toroidal dipole (TD) resonance are analyzed by a combination of the field distributions. By evaluating the sensing performance with finite difference time domain (FDTD), the highest Q-factor can reach 6900, the modulation depth is close to 100 %, the sensitivity can reach 288 nm/RIU, and the figure of merit (FOM) is 888 RIU−1. Furthermore, the sensor is prepared using electron beam lithography (EBL), and inductively coupled plasma reactive ion etch (ICP-RIE), and high sensitivity is achieved in liquids with different refractive indices in the near-infrared. The results show a good sensing performance of the designed metastructure. Our findings will give access to the development of applications in non-linear devices, narrow-band filters, optical switches, and quantum nanophotonics.

High Q-factor multiple Fano resonances in all-dielectric metasurface based on quasi-bound states in the continuum

High Q-factor multiple Fano resonances in all-dielectric metasurface based on quasi-bound states in the continuum

A high-performance multi-wavelength optical switch based on multiple Fano resonances in an all-dielectric metastructure

A high-performance multi-wavelength optical switch based on multiple Fano resonances in an all-dielectric metastructure

High-Q-factor multiple Fano resonance for sensitive refractive index sensors based on all-dielectric metasurface

High-Q-factor multiple Fano resonance for sensitive refractive index sensors based on all-dielectric metasurface

Generation of Multiple Plasmonic Fano Resonances and Detection of Distinct Analytes

Generation of Multiple Plasmonic Fano Resonances and Detection of Distinct Analytes

Investigation of Multiple High Quality-Factor Fano Resonances in Asymmetric Nanopillar Arrays for Optical Sensing

A novel asymmetric all-dielectric metasurface supporting multiple Fano resonances with high quality-factor through the excitation of quasi-bound states in the continuum is theoretically investigated. It is demonstrated that two resonances in the near-infrared wavelength are excited by the symmetry-protected bound state in the continuum, which can be transformed into the electric dipole and the toroidal dipole quasi-BIC resonance with high quality-factor by breaking the symmetry of metasurface. Moreover, the sensing properties based on different liquid refractive indexes are researched theoretically. The results show that the maximum quality-factor of the Fano resonance peak is 8422, and the sensitivity can reach 402 nm/RIU, with a maximum figure of merit of 2400 RIU−1. This research is believed to further promote the development of optical sensing and nonlinear optics.

Excitation of Multiple Fano Resonances in a Plasmonic Device and Carcinoma Detection

Excitation of Multiple Fano Resonances in a Plasmonic Device and Carcinoma Detection

Multiple Fano resonances inspired by bound states in all-dielectric double-opening resonant ring metasurfaces

Sensors are important tools in the fields of biology and chemistry. Highly sensitive, robust and low-cost sensors and their preparation methods have always constituted a research topic. In this paper, an all-dielectric metasurface with a double-opening resonant ring is proposed. The metasurfaces can support MD and ED modes to excite three q-BIC modes. And the Q-factor can reach 4.97×104, 2.02×105 and 1.39×106 respectively. For the asymmetric structure, the three excited peaks have certain polarization-insensitive characteristics. With the introduction of graphene, the dynamic regulation of transmission peak can be realized, specifically the regulation of resonance wavelength, and the intensity of transmittance. Since the all-dielectric metasurfaces assist in enhancing the interaction of the light field with dielectric materials, and the field enhancement effect is obvious, so we analyze the sensing properties of the metasurface. It has a sensitivity of up to 1340 nm/RIU and FOM can reach 1.17×106. Finally, we additionally analyze another asymmetric form, which enables the excitation of the q-BIC by changing the polarization angle, making the structure potentially valuable for optical switching as well.

High-Q Fano resonances in all-dielectric metastructures for enhanced optical biosensing applications.

Fano resonance with high Q-factor is considered to play an important role in the field of refractive index sensing. In this paper, we theoretically and experimentally investigate a refractive index sensor with high performance, realizing a new approach to excite multiple Fano resonances of high Q-factor by introducing an asymmetric parameter to generate a quasi-bound state in the continuum (BIC). Combined with the electromagnetic properties, the formation mechanism of Fano resonances in multiple different excitation modes is analyzed and the resonant modes of the three resonant peaks are analyzed as toroidal dipole (TD), magnetic quadrupole (MQ), and magnetic dipole (MD), respectively. The simulation results show that the proposed metastructure has excellent sensing properties with a Q-factor of 3668, sensitivity of 350 nm/RIU, and figure of merit (FOM) of 1000. Furthermore, the metastructure has been fabricated and investigated experimentally, and the result shows that its maximum Q-factor, sensitivity and FOM can reach 634, 233 nm/RIU and 115, respectively. The proposed metastructure is believed to further contribute to the development of biosensors, nonlinear optics, and lasers.

Multi-Wavelength Selective and Broadband Near-Infrared Plasmonic Switches in Anisotropic Plasmonic Metasurfaces.

Anisotropic plasmonic metasurfaces have attracted broad research interest since they possess novel optical properties superior to natural materials and their tremendous design flexibility. However, the realization of multi-wavelength selective plasmonic metasurfaces that have emerged as promising candidates to uncover multichannel optical devices remains a challenge associated with weak modulation depths and narrow operation bandwidth. Herein, we propose and numerically demonstrate near-infrared multi-wavelength selective passive plasmonic switching (PPS) that encompasses high ON/OFF ratios and strong modulation depths via multiple Fano resonances (FRs) in anisotropic plasmonic metasurfaces. Specifically, the double FRs can be fulfilled and dedicated to establishing tailorable near-infrared dual-wavelength PPS. The multiple FRs mediated by in-plane mirror asymmetries cause the emergence of triple-wavelength PPS, whereas the multiple FRs governed by in-plane rotational asymmetries avail the implementation of the quasi-bound states in the continuum-endowed multi-wavelength PPS with the ability to unfold a tunable broad bandwidth. In addition, the strong polarization effects with in-plane anisotropic properties further validate the existence of the polarization-resolved multi-wavelength PPS. Our results provide an alternative approach to foster the achievement of multifunctional meta-devices in optical communication and information processing.

All-dielectric metasurface with multiple Fano resonances supporting high-performance refractive index sensing

All-dielectric metasurface has important application value in many fields, especially in refractive index sensing. In this paper, an all-dielectric metasurface composed of a silicon triangular-hole nanodisk array is designed and studied numerically. Through introducing asymmetry in the proposed metasurface and transforming the bound states in the continuum (BIC) into the quasi-BIC, three sharp Fano resonances with almost 100% modulation depth can be achieved, and the highest quality factor (Q-factor) can reach 49,915. Further, the three Fano resonances can be regulated and controlled by adjusting the structural parameters. Moreover, the sensing performance of the structure is researched by changing the ambient refractive index. The maximum sensitivity obtained is 248 nm/RIU, and the best figure of merit is 3815RIU−1. The proposed structure provides a scheme for the design of optical devices, especially refractive index sensors.

Refractive index sensor based on a D-shaped resonator and a stub resonator and its slow light characteristics

In this paper, a metal–insulator–metal waveguide structure is proposed based on a D-shaped resonator and a stub resonator, and it can generate multiple Fano resonances. The magnetic field (Z-direction) distribution and transmission spectrum of the structure are analyzed by the finite element method (FEM). The theory results are performed with the multimode interference coupled mode theory (MICMT), and they show high agreement with the simulation outcomes. The calculations also discuss the effect of structural parameters on the transmission spectrum. Moreover, the structure’s sensing characteristics are analyzed in detail, achieving a maximum sensitivity and FOM* of 1300 nm/RIU and 181.44, respectively. In addition, the slow light properties of the structure are also investigated, whose group delay and group index can reach 0.24 ps and 48.93, respectively. The group delay time is dynamically regulated by controlling the number of D-shaped resonators to achieve the effect of a delay line. It can provide some reference value for multifunctional on-chip optical integrated devices based on MIM waveguide structure.