Fano Resonance Wavelength Research Articles

Electrical field-induced Fano resonance tunability in photonic crystal slabs

The creation of tunable Fano resonances in a photonic crystal structure with a side-coupled nanocavity and a waveguide with a partially transmitting element is investigated in this paper. In the proposed structure, the nanocavity’s central hole is made up of two cylinders with different radii that are nested inside each other. The outer and inner cylinders are made of quartz and liquid crystal, respectively. The performance of this device is analyzed using the three-dimensional finite-difference time-domain. The transmission spectrum, resonance wavelength, and quality factor of the proposed structure are calculated for various applied voltages. It is demonstrated that as the applied voltage increases, the quality factor changes and the Fano resonance wavelength shifts. Based on the findings, a tuning range of 5.2 nm is achievable with an excellent transmission contrast within this range. The presented structure is appropriate for applications such as tunable switches and filters.

Optical non-volatile correction of SERS wavelength using optical pumping

In this paper, we propose a reconfigurable two-dimensional photonic crystal (PC) made from a new ultralow loss phase change material for detecting and imaging applications of surface-enhanced Raman scattering (SERS). The proposed all-dielectric structure is composed of identical holes periodically distributed on Sb2S3 as a substrate, tuned by optical pumping. The proposed PC is investigated using full-wave simulation of the CST with the finite-difference frequency domain method over a wide bandwidth of optical wavelengths. In this study, compensation for the error of the Fano resonance wavelength due to the fabrication process is realized through tuning optical pumping applied to the configuration. Also, the numerical results show the designed PC supports two high-quality Fano resonance modes, leading to uniform and high field enhancement with a SERS enhancement factor of 1.23 × 1012, which is significant for the application of SERS enhancement.

Glycerol concentration sensor based on the MIM waveguide structure

Glycerol is widely used in medicine, industry and skin care products. This study investigated a high-sensitivity glycerol concentration sensor based on double Fano resonances in a metal-insulator-metal (MIM) waveguide structure, established a coupling model of a baffle waveguide (BW) and a circular split ring resonator (CSRR), and generated asymmetric double Fano resonances in the waveguide structure. The Fano resonance transmittance reached 0.82, and the linear relationship between the refractive index (RI) and the glycerol concentration was obtained using the sensitivity of the Fano resonance spectrum. The application of the proposed sensor for glycerol concentration detection revealed that the Fano resonance wavelength was redshifted with the RI and that the sensing sensitivity reached 1153.85 nm/refractive index unit (RIU); therefore, the quick detection of the corresponding glycerol concentration can be realized. This proposed structure has significance in the research of optical sensors and optical switches.

Fully Reconfigurable Fano Resonator on a Silicon Photonic Chip

A fully reconfigurable Fano resonator on a silicon photonic chip is reported. The Fano resonator is realized with the use of an add-drop micro-disk resonator (MDR) and a Mach-Zehnder interferometer (MZI). The waveguides at the through and drop ports of the MDR connect to two spiral waveguide arms of the MZI directly. Two independent metallic micro-heaters are incorporated on top of the MDR and the lower arm of the MZI. Thanks to the resonant mode interference between the MDR and the MZI, the Fano resonance occurs. By thermal tuning the resonance coupling between the MDR and the MZI, the generated Fano resonance is fully tunable. In addition to the independent tunable slope rate (SR) and the resonance wavelength, the Fano resonance wavelength can shift while its line shape remains by simultaneously controlling the two micro-heaters. A chip is designed, fabricated and evaluated. The measurement results show that the static Fano resonance has a line shape with an extinction ratio (ER) of 17.1 dB and SR of −13.6 dB/nm. By simultaneously controlling the two micro-heaters, full reconfigurability of the Fano resonance is demonstrated. Thanks to its straightforward configuration, the proposed Fano resonator holds the key advantage in terms of ultra-compactness and fully reconfigurability, which offers a great potential for applications such as on-chip optical switching, modulation and microwave photonics applications.

Multimode Fano Resonances Sensing Based on a Non-Through MIM Waveguide with a Square Split-Ring Resonance Cavity.

In this article, a non-through metal–insulator–metal (MIM) waveguide that can excite fivefold Fano resonances is reported. The Fano resonances are obtained by the interaction between the modes excited by the square split-ring resonator (SSRC) and the bus waveguide. After a detailed analysis of the transmission characteristics and magnetic field strength of the structure using the finite element method (FEM), it was found that the independent tuning of Fano resonance wavelength and transmittance can be achieved by adjusting the geometric parameters of SSRC. In addition, after optimizing the geometric parameters, the refractive index sensing sensitivity (S) and figure of merit (FOM) of the structure can be optimal, which are 1290.2 nm/RIU and 3.6 × 104, respectively. Additionally, the annular cavity of the MIM waveguide structure can also be filled with biomass solution to act as a biosensor. On this basis, the structure can be produced for optical refractive index sensing in the biological, micro and nano fields.

Dynamically tunable refractive index sensor based on Fano resonance with metal-insulator-metal-graphene nanotube hybrid structure

In practical applications, the performances of conventional metal-insulator-metal (MIM) waveguide structured optical devices cured during fabrication are not dynamically tunable. In order to address the problem that such devices are not dynamically tunable, based on the excellent optoelectronic properties of graphene materials, graphene nanotubes are induced into the metal-insulator-metal waveguide coupled circular resonant cavity structure, thus designing a dynamically tunable MIM-graphene nanotube hybrid structure refractive index sensor in this work. The finite element method (FEM) is used to numerically study the transmission characteristics, electric field distribution and magnetic field distribution of the system, and the theoretical analysis is performed by multimode interference coupled mode theory (MICMT) to verify its correctness. The results show that after adding graphene nanotube to the MIM waveguide coupled ring resonant cavity structure, a Fano resonance peak appears in this system, which originates from the coherent coupling between the TM<sub>10</sub> cavity resonance mode and the graphene plasmonic electrical resonance mode. The sensor can dynamically tune the resonance wavelength and linewidth of Fano resonance in a wide wavelength range by changing the chemical potential of graphene, thus realizing the performance tuning of the refractive index sensor. Hence, the problem that the conventional plasma refractive index sensor is not dynamically tunable issolved. In addition, the influence of the geometrical parameters of the structure on the sensing performance of this system is also studied in detail. The sensor sensitivity increases up to 1250 nm/RIU and the quality factor rises up to 42.4 RIU<sup>–1</sup> at the optimal structural parameters. Compared with the traditional metal-insulator-metal waveguide structure design, this device has many merits such as wide operating band range, easy processing and dynamic tunability, which is a guideline for designing the dynamically tunable high performance nano-photonic integrated devices.

New Optical Method for the Sucrose Solution Measurement Based on Fano Resonance

We propose a new method to determine the concentration of a sucrose solution based on Fano resonance, demonstrate that the [Formula: see text]-shaped resonator and rectangular resonator structures can realize the Fano resonance, observe higher sensitivity up to 2142 nm/RIU, and use the structure to measure the concentration of a sucrose solution. This work shows that the Fano resonance wavelength removed to longer wavelengths as the concentration of the solution increased, and the resolution of solution concentration is [Formula: see text], which can be used for measuring the concentration of solutions other than sucrose. This research is an important first step towards creating the industrial application of photon properties to extend photon polariton applications throughout the infrared.

Flexible standing-wave-node adjustment in square cavity to facilitate Fano resonance and nanosensing analyses

The influencing factors and modulating effects of Fano resonance in a plasmonic metal–insulator–metal waveguide Fano system have been extensively studied in the past. While standing wave node of the electromagnetic field in the resonator in the Fano system, which can play a good and flexible regulating role in Fano resonance in its own way, has not been systematically studied. In view of the important and special influence of standing wave nodes on Fano resonance, it is necessary to be studied systematically. This study investigates a plasmonic Fano-resonance system comprising a metal–insulator–metal waveguide and stub resonator, which is side-coupled to a square-cavity resonator. The variations in the transmission properties of the system corresponding to changes in its different geometric parameters are investigated via finite-element analyses. Furthermore, the peak Fano-resonance wavelength equation deduced in this study is applied in combination with the standing-wave theory to explain the Fano-resonance phenomenon. The results obtained reveal that the effect of the nodes corresponding to the standing-wave modes (1, 0) and (1, 1) in square/rectangular cavities facilitates the remarkable and flexible regulation of Fano resonances corresponding to the said modes as the stub shifts from the horizontally self-symmetric to the self-asymmetric orientation about the vertical nodal lines. The formation mechanism of standing-wave-node adjustment in square cavity to facilitate Fano resonance is analyzed. When the stub remains horizontally self-asymmetric about the vertical nodal lines of the mode (0, 1), the first-order mode in the square cavities, which facilitates the realization of Fano resonance, is dual in nature and comprises the (0, 1) and (1, 0) modes. It is confirmed that more favorable relative positions of the stub and the square cavity result in a higher probability of realizing Fano resonance Six instances of Fano resonance of the structure comprising two single-side-coupled square cavities are realized in this study. The coupling arrangement is such that the Fano resonance remains unaffected by the standing-wave nodes in the square cavities. The proposed structure demonstrates a sensitivity of 1128 nm/RIU (RIU: refractive index unit). Furthermore, the geometric parameters are optimized considering a fixed environmental refractive index of 1.04. The resulting optimum figure of merit equals 2.76 × 104. The proposed plasmonic Fano system demonstrates great potential for use in micro–nano photonic integrated circuits and high-sensitivity sensors.

Detecting the temperature of ethanol based on Fano resonance spectra obtained using a metal-insulator-metal waveguide with SiO2 branches

Based on the transmission characteristics of surface plasmon polaritons (SPPs) in sub-wavelength structures, this paper proposes a metal-insulator-metal (MIM) waveguide structure composed of a main waveguide with glass (SiO2) branches (WWGB) coupled with an elliptical split-ring resonance cavity (ESRRC). WWGB has a broadband continuous transmission spectrum, while ESRRC has a narrow-band discrete transmission spectrum. The coupling and interference between the two can generate excited dual-Fano resonance, with sensitivities and figures of merits (FOM) of 800 nm/RIU, 1150 nm/RIU, and 9.88, 104.55, respectively. After adding SiO2 branches to both sides of the main waveguide, the FOM are enhanced to 28.57 and 127.78, representing increases of 189% and 22.15%, respectively. This structure can be applied as a temperature sensor. After filling the cavity of the to-be-tested material with 75% ethanol, as the temperature increases, the Fano resonance wavelength to drift, therefore, the corresponding temperature can be calculated by the Fano resonance wavelength. Experiments show that the proposed MIM waveguide has a maximum sensitivity of 1406.25 nm/RIU, an FOM of 156.25, and a temperature sensitivity of 0.45 nm/℃. Ultimately, the results demonstrate that incorporating SiO2 branches enhances the sensing characteristics of the MIM waveguide, after adding ethanol, the MIM can be applied to temperature sensors, with a high sensitivity of 1406.25 nm/RIU, thereby providing a new design strategy for producing high-performance waveguides.

Fano Resonance Ion Sensor Enabled by 2D Plasmonic Sub-Nanopores-Material

Silicon photonics has shown great potential in integrated biochemical sensing. However, it is challenging to detect ions selectively, which is crucial in several biochemical application. In this paper, we propose and demonstrate a newly designed ion sensor by combining two-dimensional (2D) plasmonic and sub-nanoporous K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> MoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> with a silicon waveguide. A T-shaped waveguide coupled with a microring resonator (MRR) generates Fano resonance at all resonance modes. Sharp Fano-like spectra were optimized by numerically simulating the structure of the waveguide in terms of the coupling coefficients, phase factor, and MRR power loss. In our design, a Fano resonance wavelength shift is caused by a refractive index change based on the interaction between 2D near-infrared plasmonic K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> MoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> . Moreover, the alteration in plasmonic absorption leads to a variation in transmission power. This dual-sensing output method is unique compared with existing methods that utilize optical ion sensors. Our results demonstrate that the micro-scale silicon waveguide combined with a 2D plasmonic material exhibits excellent potential as a chemical sensor.

Optical sensing based on multimode Fano resonances in metal-insulator-metal waveguide systems with X-shaped resonant cavities

A plasmonic metal-insulator-metal (MIM) waveguide system is proposed, which is composed of a symmetrical X-shaped resonant cavity and a bus waveguide with a baffle, and its Fano resonance and optical sensing characteristics are investigated by using the finite element method (FEM). The results show that the system allows easy implementation of up to four Fano resonances, and the maximum refractive index sensitivity and figure of merit are 1303 nm/RIU and 3113, respectively. The influences of the geometric parameters of the system on the Fano resonances are also investigated, and further the independent adjustments of the Fano resonance line shape and wavelength are realized. Moreover, when an additional X-shaped resonant cavity is added to the system, more ultrasharp Fano resonances with considerable performances are obtained, which may enhance the parallel processing capability of the system. The proposed plasmonic MIM waveguide system may have potential applications in integrated photonic devices and nanoscale optical sensing.

Fano-resonance-based refractive index sensor with ultra-high sensitivity

In this paper, we propose a Fano-resonance-based refractive index sensor with ultra-high sensitivity. The sensor comprises a metal–insulator-metal (MIM) waveguide with two rectangular stubs coupled with a circular resonator embedded with a defective metal nanocube (CRMN). The transmission characteristics of the structure are simulated using the 2D finite element method. This analysis reveals that the Fano resonance mode splitting is affected by the geometry of the sensor. In addition, the modulation depth and position of the Fano resonance can be tuned by adjusting the width and length of the stub on the CRMN. Optimizing the structural parameters results in a peak sensing sensitivity of 10200 nm∙RIU−1 under the ultra-compact sensor size. This sensitivity allows the sensor to be used in the detection of hemoglobin concentration (HC). By processing simulation data, the linear relationship between the refractive index of three different blood groups (A, B, and O) and HC is obtained. Based on the sensing principle of the designed device, HC can be calculated from measuring the shift of the Fano resonance wavelength. These results provide critical developments for the application of nanoscale refractive index sensors in the biomedical field.

Active Manipulation of Fano Resonance at Visible and Near-Infrared Wavelengths in Metal Plasmonic Nanodevices Using Graphene

Active manipulation of Fano resonance at visible and near-IR wavelengths in metal nanodevices is one of the important challenges for applications such as chemical and biological sensing. Here, we theoretically research an active manipulation of Fano resonance at visible and near-IR wavelengths in gold plasmonic nanodevices with graphene. The surface plasmon resonance of the gold plasmonic nanodevice with graphene has three resonance peaks, and this can be explained by the distribution of the electric field in the nanodevice. The Fano resonance wavelength of the gold plasmonic nanodevice with graphene has a significant blue-shift compared with the gold nanodevices without graphene. Moreover, the Fano resonance depends on the length and position of Au nanorods and the environment refractive index. The figure of merit of the gold nanodevice with graphene can be as high as 44.1, which makes the system suitable for high sensitivity applications. Finally, we actively manipulate the absorption spectrum and the reflected light phase through changing the Fermi energy of graphene. These results suggest an original method for the design of an actively manipulated Fano resonance nanodevice.

Novel Crescent-Shaped Cavity Resonator Based on Fano Resonance Spectrum

World is rich in unconventional oil and various alternatives to petroleum. However, conventional oil production declines so quickly that it is likely these unconventional oil resources cannot be put into production fast enough and thus will not be compensated sufficiently. We realize detecting rapid detection of water content in heavy oil. The waveguide consists of a metal-insulator-metal (MIM) waveguide, rectangular cavity resonator, and crescent-shaped cavity resonator. The effects of the coupling distance, geometry of the crescent-shaped cavity resonator and its rotation angle, and length and width of the rectangular cavity resonator on the Fano resonance lines were numerically analyzed. Multiple Fano resonances can be produced as the rotation angle of the crescent-shaped cavity resonator is adjusted, and the sensor’s refractive index sensitivity was found to be $$935.71\mathrm{ nm}/\mathrm{RIU}$$ . By measuring the water content in heavy oil, we found that the Fano resonance lines shift toward shorter wavelengths as the volume fraction of water content increases. The detection resolution in heavy oil $$1.79\times {10}^{-9}$$ . The results presented here show that water content in heavy oil can be calculated using the measured change in the Fano resonance wavelength.

Extremely high figure of merit in all-dielectric split asymmetric arc metasurface for refractive index sensing

In this paper, we have proposed the design of an all-dielectric metasurface that consists of a 2-dimensional periodic array of split asymmetric silicon arcs, making closed rings, on a silica substrate. The numerical simulation shows that the proposed metasurface exhibit Fano resonance due to close loop current density in asymmetric silicon arcs, at the wavelength of 967 nm for air as analyte surrounding the metasurface. The maximum achieved spectral contrast of the Fano resonance peak is 99%. It is also observed from the numerical simulation that the Fano-resonance wavelength and its linewidth is dependent on the refractive index and the thickness of the analyte above the silica substrate. The calculated sensitivity, quality factor (Q-Factor) and extremely high figure of merit (FoM) of the proposed sensor are 324 nm/RIU, 8720 and 2465, respectively.

Fano resonances based on plasmonic square resonator with high figure of merits and its application in glucose concentrations sensing

A compact plasmonic structure is proposed employing symmetrical metal–insulator-metal (MIM) waveguides coupled to the square resonator for nano-sensing applications, especially for water glucose sensing. Finite difference time domain method is chosen to derivate the output characteristics and magnetic-field distributions. Outcomes illustrate the Fano resonance in the output characteristics can be simply managed by varying the inner and outer lengths and the refractive index of the square cavity. Also, between Fano resonance wavelength and resonator length, a linear behavior exists. These features suggest that physical parameters provide flexibility to propose the structure. Our plasmonic device produces a sensitivity and figure of merit of about 6400 nm/RIU and 1 × 104, respectively. By utilizing the mathematical model for water refractive index, we aim to develop a sensor structure to detect the glucose concentration in water. This designed sensor may discover significant applications in future nanosensing domain.

Magnetic Fano resonance in silicon concentric nanoring resonator dimers under azimuthally polarized beam excitation

Abstract In this work, we proposed an all-dielectric nanostructure composed of silicon concentric nanoring resonator dimers (Si CNRD). We studied the scattering properties of Si CNRD and demonstrated the magnetic Fano resonance resulting from the interference between a narrow magnetic dipole mode and a broad magnetic dipole mode coupled into Si CNRD excited by an azimuthally polarized beam (APB). The spectral characteristics of the magnetic Fano resonance are characterized quantitatively by a coupled oscillator model. By changing the geometric parameters of the Si CNRD, the wavelength and intensity of the magnetic Fano resonance can be effectively adjusted. The nanostructure we proposed exhibits potential applications in low-loss sensors, nonlinearity, and laser devices.

Enhancement of absorption of molybdenum disulfide monolayer on low-index contrast dielectric grating in the visible regions

A design consists of low-index contrast grating is proposed to achieve the narrow absorption response for two-dimensional (2D) materials such as a MoS2 monolayer in the visible wavelength regime. High absorption occurs at the wavelength of Fano resonance for both transverse dielectric (TE) and transverse magnetic (TM) polarizations. It is proved that by manipulating related structural parameters and the incident angle, the peak wavelengths of MoS2 absorption can be tuned in a wide range. In addition, an improved structure with MoS2 ribbons is proposed to further boost the light-MoS2 interaction. The relationships between the absorptance and the period and width of MoS2 ribbons are discussed. The proposed optical devices could be efficiently exploited as tunable absorbing structures for optoelectronics and photovoltaic devices in the visible region.

Fano resonances of a ring-shaped “hexamer” cluster at near-infrared wavelength

Fano resonances have been studied intensely in the last decade, since it is an important way to decrease the resonance line width and enhance local electric field. However, achieving a Fano line-shape with both narrow line width and high spectral contrast ratio is still a challenge. In this paper, we theoretically predict the Fano resonance induced by the extinction of normal plane wave in a ring-shaped hexamer cluster at near-infrared wavelength. In order to obtain the narrow Fano line width and high spectral contrast ratio, the relationships between the Fano line-shape and the parameters of the nanostructure are analyzed in detail. The nanostructure is simulated by using commercial software based on finite element method. The simulation results show that when the structural parameters are optimized, the Fano line width can be narrowed down 0.028 eV with a contrast ratio of 86%, and the local electric field enhancement factor at the Fano resonance wavelength can reach to 36. Furthermore, the effective mode volume of the structure is 3.9×10−23m3 which is lower than the available literature. These results indicate many potential applications of the Fano resonance in multiwavelength surface-enhanced Raman scattering and biosensing.

Compact tunable electromagnetically induced transparency and Fano resonance on silicon platform.

We propose and demonstrate an on-chip coupling resonant system to generate electromagnetically induced transparency (EIT)-like effect and Fano resonance on silicon platform. It is composed of a microring resonator (MRR) and two cascaded Sagnac-loop mirrors (SLMs) assisted Fabry-Perot (FP) cavity on silicon-on-insulator. According to the coupling conditions of the MRR, two cases are studied theoretically. When the MRR is over coupling, EIT-like transmission can be observed. In contrast, Fano resonances can be generated by the condition of under coupling. In the experiment, the add-drop MRR is under coupling, leading to a sharp asymmetric line shape for Fano resonance. The resonance wavelength of the MRR can be dynamically tuned based on thermal-optic effects by tuning the micro-heater. The experiment results show Fano resonances with maximum extinction ratio (ER) of 23.22 dB and maximum slope rate (SR) of 252 dB/nm. Moreover, the wavelength of Fano resonance can be shifted widely with a tuning efficiency of 0.2335 nm/mW.