Metal-insulator-metal Waveguide Structure Research Articles

Narrow-band notch filter and refractive index sensor based on rectangular-semi-annular cavity coupled with MIM waveguide structure

In this work, a symmetric structure based on a metal-insulator-metal (MIM) waveguide is proposed for narrow-band notch filters and refractive index sensors. The structure comprises a symmetrically intersecting rectangular-semi-annular cavity and a long straight waveguide. The transmission spectrum and magnetic field distribution of the notch filter are studied and analyzed by the finite element method (FEM) with scattering boundary conditions (SBC). Our analysis reveals that the band-stop filter exhibits a minimum transmittance of 0.35%, a bandwidth of 34 nm, and a quality factor (Q) of 35.16. These characteristics include low stop-band transmittance, a narrow bandwidth, and a high Q value. Furthermore, our structure allows for independent adjustment of the narrow band filtering range by varying geometric parameters such as H, d, R1, and d. Additionly, we conduct theoretical analysis to investigate the sensing properties of the structure. The refractive index sensitivity of the structure reaches a high value of 1222 nm RIU−1, accompanied by a figure of merit(FOM*) of up to 175.9. These results demonstrate the structure’s excellent filtering properties and high-sensitivity sensing characteristics.Consequently, it holds significant potential for application in high-density integrated circuits and nano-optics.

A dual-purpose sensor with a sawtooth U-shaped cavity and a rectangle-shaped cavity in a MIM waveguide structure

To improve the performance of subwavelength refractive index and temperature sensors, this paper proposes a subwavelength metal-insulator-metal (MIM) waveguide structure consisting of a sawtooth U-shaped cavity and a rectangular cavity based on surface plasmon polaritons. The transmission spectrum of the system is simulated using the finite element method (FEM) and verified with multi-mode interference coupled-mode theory (MICMT). The results demonstrate excellent sensing characteristics for the system, with a refractive index sensitivity of 1300 nm RIU−1, a figure of merit (FOM*) of 191.262, and a temperature sensitivity of 0.525 nm/°C. This indicates that the nano-plasma system is highly significant in refractive index and temperature sensing.

Tunable plasmonically-induced reflection in MIM waveguide structure with split ring resonator

A novel plasmonic waveguide structure consisting of a rectangular resonator side coupled with a split ring resonator (SRR) and a metal–insulator–metal (MIM) waveguide with metal baffle was proposed. The transmission characteristics of the present structure were simulated by a finite-difference time-domain (FDTD) method. The results show that the structure can realize three typical plasmonically-induced reflection (PIR) windows. Meantime, the PIR window can be tuned vertically and horizontally, respectively, and multiple PIR windows with different wavelength intervals can also be obtained by changing the split position. In addition, the sensitivity of the proposed structure can reach up to 1,075[Formula: see text]nm/RIU. Furthermore, a rectangular resonator was added to the other side of the plasmonic waveguide structure for realizing the dual-channel PIR window. Another SRR was added to form a symmetrical structure, which further improved the sensitivity and transmittance. Undoubtedly, the proposed structure will have potential applications in sensor and optical switches.

Quadruple Fano resonances in MIM waveguide structure with ring cavities for multisolution concentration sensing.

In this paper, a metal-insulator-metal (MIM) waveguide structure is proposed to produce quadruple Fano resonances, which is composed of a side-coupled elliptical cavity, a half-ring cavity, a half-ring cavity with an opening, and a bus waveguide with a circular barrier. The simulation results show that the resonant wavelengths of the quadruple Fano resonances can be almost independently tuned by changing the structural parameters of the three cavities. The refractive index sensing based on different cavities is discussed, and the maximum sensitivity is 1048.6nm/RIU with an excellent linear-sensing relationship. Finally, the simultaneous multisolution concentration sensing is demonstrated, and the sensitivities are 0.138n m L -1 g -1 for the plasma concentration, 0.120n m L -1 g -1 for the glucose solution concentration, and 0.180n m L -1 g -1 for the N H 4 C l solution concentration. The results are conducive to promoting the applications of MIM waveguide structures in integrated optical sensing.

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.

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.

Multiparameter Sensing Based on Tunable Fano Resonances in MIM Waveguide Structure with Square-Ring and Triangular Cavities

In this paper, a metal–insulator–metal (MIM) surface plasmon waveguide structure is proposed and numerically investigated. It is composed of a square-ring cavity with a silver baffle, an isosceles triangle cavity, and a bus waveguide with a silver baffle. The results show that the structure can produce triple Fano resonances that can be independently tuned by changing the structural parameters. The detection of refractive indexes at different positions in the structure was also accomplished, with a maximum sensitivity of 2259.56 nm/RIU. On the basis of this, the simultaneous measurement of multiple parameters (plasma concentration and glucose concentration) was performed. The numerical simulation results are beneficial to the applications of MIM waveguide structure in nanosensing and biosensing with time-sharing or simultaneous measurement of multiple parameters.

Nanoplasmonic Directional Coupler Using Asymmetric Parallel Coupled MIM Waveguides

This article presents the design and analysis of a nanoplasmonic directional coupler using an asymmetric parallel-coupled line metal insulator metal (MIM) waveguide. The proposed plasmonic directional coupler is designed by applying three wire transmission line (TL) model based on the basic TL characteristic parameters of the related asymmetric parallel coupled line structures. To this end, the effective refractive index, propagation length, and characteristic impedance of the related coupled line MIM waveguide structure are obtained by using fullwave simulation software CST microwave studio suite. Specifically, the dual-band nature can be obtained by exchanging the asymmetric coupled line MIM waveguide section with two asymmetric even mode step impedance resonators (SIRs) by adjusting the gap width (g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ). Subsequently, a side-coupled resonator is designed and analyzed. Hence, the designed coupler is more useful to exchange several plasmonic devices such as power splitters and mixers in photonic integrated circuits (PICs) at a subwavelength scale.

A MIM Waveguide Structure of a High-Performance Refractive Index and Temperature Sensor Based on Fano Resonance

A plasmonic refractive index nanosensor structure consisting of a metal-insulator-metal (MIM) waveguide with two symmetrical rectangle baffles coupled with a connected-concentric-double rings resonator (CCDRR) is presented. In this study, its transmission characteristics were investigated using the finite element method (FEM). The consequences, studied via simulation, revealed that the transmission spectrum of the system presents a sharp asymmetric Fano profile due to the destructive interference between the wide-band mode of two rectangle baffles on the bus waveguide and the narrow-band mode of the CCDRR. The effects of the geometric parameters of the structure on the transmission characteristics were investigated comprehensively. A sensitivity of 2260 nm/RIU and figure of merit (FOM) of 56.5 were the best levels of performance that the designed structure could achieve. In addition, the system could act as a sensor for use for temperature sensing, with a sensitivity that could reach 1.48 nm/°C. The designed structure advances with technology with new detection positions and has good application prospects in other high-sensitivity nanosensor fields, for example, acting as a biosensor to detect the hemoglobin level in the blood.

Independently tunable triple Fano resonances based on MIM waveguide structure with a semi-ring cavity and its sensing characteristics

In this paper, a metal-insulator-metal (MIM) waveguide structure consisting of a side-coupled rectangular cavity (SCRC), a rightward opening semi-ring cavity (ROSRC), and a bus waveguide is reported. The finite element method is used to analyze the transmission characteristics and magnetic-field distributions of the structure in detail. The structure can support triple Fano resonances, and the Fano resonances can be tuned independently by altering the geometric parameters of the structure. Moreover, the structure can be applied in refractive index sensing and biosensing. The maximum sensitivity of refractive index sensing is up to 1550.38 nm/RIU, and there is a good linear relationship between resonance wavelength and refractive index. The MIM waveguide structure has potential applications in optical on-chip nano-sensing.

MIM waveguide structure consisting of two triangle stubs, side-coupled with an eight-like resonant cavity

Herein, a Fano resonance based optical sensor with high sensitivity is proposed. The sensor comprises a metal–insulator–metal (MIM) waveguide with two symmetric triangle stubs, side-coupled with a square ring resonator with a stub (SRS). Utilizing the 2D finite element algorithm, the transmission characteristics of the MIM waveguide structure are systematically explored. This analysis reveals that the coupling effect between the MIM waveguide and the SRS leads to the appearance of Fano resonance. After using a polydimethylsiloxane (PDMS)-sealed resonator, an outstanding temperature sensitivity of −20.3 nm/∘C is obtained. In addition, the influence of the width of the MIM waveguide, the coupling distance, the distance between two symmetric triangle stubs and the geometric parameters of the resonator on the Fano resonance line is also studied in detail. Optimizing these structural parameters results in a peak refractive index (RI) sensitivity of 6000 nm/RIU, and the figure of merit (FOM) is 17RIU−1. These results not only help to narrow the gap with the optical fiber sensor, but also pave the way for the design and application of ultra-high sensitive RI sensor and temperature sensor.

Tunable Multiple Fano Resonances and Stable Plasmonic Band-Stop Filter Based on a Metal-Insulator-Metal Waveguide

A metal-insulator-metal (MIM) waveguide consisting of two stub resonators and a ring resonator is proposed, which can be used as refractive index sensor and stop-band filter at the same time. The transmission characteristics of the MIM waveguide structure is studied by the finite element method (FEM). The simulation results show that the typical Fano profile and multiple Fano resonances can be achieved. According to the analysis, the range of stop-band and the multiple Fano resonance positions can be adjusted flexibly and independently by adjusting the aggregate parameters of the MIM waveguide structure. Moreover, it is also found that the two Fano resonances at both ends of the stop band can be determined by the two stubs, and the other two Fano resonances are regulated by the ring resonator. In addition, the spectral position of multi-Fano resonances is highly sensitive to the radius of the ring resonator and the refractive index of the filled medium. The maximum sensitivity and the figure of merit (FOM) of the MIM waveguide structure are 1650 nm/RIU and 117.8 in magnitude, respectively. These results provide a reference for implementing high-sensitivity sensors and large-bandwidth stop-band filter in MIM waveguide coupling systems based on multi-Fano resonance effect.

Optical refractive index sensor with Fano resonance based on original MIM waveguide structure

In recent years, optical refractive index sensors have received significant attention in the field of chemical and biological sensing owing to the advantages of small size. In order to achieve the requirements of small structure and high sensitivity of nano refractive index sensing, this paper proposes a Fano resonance–based waveguide structure in which a metal-insulator-metal (MIM) structure using surface plasmons and U-shaped cavities are coupled unilaterally. The transmittance spectrum of the waveguide-coupled resonator with different incident light wavelengths can be obtained. The U-shaped cavity and semi-annular straight waveguide are superimposed on and coupled to each other to form the Fano resonance transmittance spectrum. An extremely narrow impedance is formed in the transmittance spectrum. The proposed structure can obtain superior sensing performance at the nanoscale after the optimisation. The results confirm that the sensing sensitivity of the refractive index of the optimised waveguide structure can achieve up to 825 nm/RIU. The results of experiments show that this structure could accurately identify the five proposed pure edible vegetable oils at room temperature. But experiments have also shown that it could not effectively distinguish between the five proposed mixed edible vegetable oils. This structure provides an effective reference for the design and development of refractive index sensors for application to pure edible vegetable oils.

Fano resonance based on D-shaped waveguide structure and its application for human hemoglobin detection.

Fano resonance is a pervasive resonance phenomenon which can be applied to high sensitivity sensing, perfect absorption, electromagnetic-induced transparency, and slow-light photonic devices. In this paper, we propose a metal-insulator-metal (MIM) waveguide structure consisting of a D-shaped cavity and a bus waveguide with a silver-air-silver barrier. The Fano resonance can be achieved by the interaction between the D-shaped cavity and the bus waveguide. The finite element method is used to analyze the transmission characteristics and magnetic-field distributions of the structure in detail. Simulation results show the Fano resonance can be adjusted by altering the geometric parameters of the MIM waveguide structure or the refractive index of the D-shaped cavity. The maximum refractive index sensitivity of the structure can reach up to 1510 nm/RIU, and there is a good linear relationship between resonance wavelength and refractive index. Since it has good sensitivity and tunability, the MIM waveguide structure can be used in bio-sensing, such as human hemoglobin detection. We show its applicability for the detection of three different human blood groups as well.

MIM waveguide structure consisting of a semicircular resonant cavity coupled with a key-shaped resonant cavity.

We describe the optical transmission properties of a surface plasmon polariton waveguide structure consisting of a metal-insulator-metal (MIM) waveguide and a semicircular resonant cavity coupled with a key-shaped resonant cavity. Finite element algorithm simulated the optical response of a MIM waveguide structure. The influence of coupling length, geometrical size, and asymmetry of the key-shaped cavity and the radius of the semicircular resonant cavity on the Fano resonance line was investigated. Results demonstrate that variation of the key-shaped cavity asymmetry leads to the appearance of dual Fano resonances. When materials with different refractive index fill in the key-shaped cavity, the MIM waveguide structure achieves a sensitivity of 1261.67 nm/RIU. This performance allows the waveguide to be used for nanoscale biosensor applications such as measuring glucose concentrations. We simulated various spiked glucose concentrations by calculating the frequency shift as the second Fano resonance line moves towards longer wavelength. Glucose concentrations were calculated from variations of the Fano resonant wavelength. The waveguide structure proposed in this paper shows impressive practical prospects for many applications in the chemical sensing and biomedical fields.

Tunable plasmonically induced reflection in HRR-coupled MIM waveguide structure

In this paper, a surface plasmon optical waveguide filter with half-ring resonator (HRR) based on the metal-insulator-metal (MIM) structure was designed and numerically simulated. The results show that the transmission characteristics of the structure tuned dynamically by altering the geometrical parameters. In addition, by tuning the refractive index of the filling material in the resonator, the designed waveguide structure realized a nanoscale refractive index sensor (753nm/RIU of sensitivity). Moreover, double plasmonic induced reflection (PIR) window was also achieved by adding another rectangular resonator. The as-designed structure also offers a potential method for optoelectronic devices.

Refractive Index Sensor Based on Fano Resonances in Plasmonic Waveguide With Dual Side-Coupled Ring Resonators

A refractive index sensor based on Fano resonances in metal-insulator-metal (MIM) waveguides coupled with rectangular and dual side rings resonators is proposed. The sensing properties are numerically simulated by the finite element method (FEM). For the interaction of the narrow-band spectral response and the broadband spectral response caused by the side-coupled resonators and the rectangular resonator, respectively, the transmission spectra exhibit a sharp and asymmetric profile. Results are analyzed using the coupled-mode theory based on the transmission line theory. The coupled mode theory is employed to explain the Fano resonance effect. The results show that with an increase in the refractive index of the fill dielectric material in the slot of the system, the Fano resonance peak exhibits a remarkable red shift. Through the optimization of structural parameters, we achieve a theoretical value of the refractive index sensitivity (S) as high as 1160 nm/RIU, and the corresponding sensing resolution is 8.62 × 10–5 RIU. In addition, the coupled MIM waveguide structure can be easily extended to other similar compact structures to realize the sensing task and integrated with other photonic devices at the chip scale. This work paves the way toward the sensitive nanometer scale refractive index sensor for design and application.

Tunable Fano Resonance in Asymmetric MIM Waveguide Structure.

A plasmonic waveguide coupled system that uses a metal-insulator-metal (MIM) waveguide with two silver baffles and a coupled ring cavity is proposed in this study. The transmission properties of the plasmonic system were investigated using the finite element method. The simulation results show a Fano profile in the transmission spectrum, which was caused by the interaction of the broadband resonance of the Fabry-Perot (F-P) cavity and the narrow band resonance of the ring cavity. The Fabry-Perot (F-P) cavity in this case was formed by two silver baffles dividing the MIM waveguide. The maximum sensitivity of 718 nm/RIU and the maximum figure of merit of 4354 were achieved. Furthermore, the effects of the structural parameters of the F-P cavity and the ring cavity on the transmission properties of the plasmonic system were analyzed. The results can provide a guide for designing highly sensitive on-chip sensors based on surface plasmon polaritons.

The sensing characteristics based on electromagnetically-induced transparency-like response in double-sided stub and a nanodisk waveguide system

We propose a novel metal–insulator–metal (MIM) waveguide structure consisting of a stub and a double side-coupled nanodisk. Its electromagnetically-induced transparency (EIT)-like response and transmission properties are numerically investigated by the finite element method (FEM). Numerical simulation results show that the EIT-like phenomenon appears in the transmission spectra. The transparency window can not only be manipulated by changing the radius of the nanodisk and the height of the stub, but also appear redshifted with the increasing of the refractive index n. Furthermore, the MIM waveguide structure is easy to yield a high sensitivity of 1200 nm/RIU with a figure of merit about [Formula: see text], which may be applied to nanosensors. These results would help us design the high-performance plasmonic devices based on the EIT-like response.

Refractive Index Sensor Based on Fano Resonances in Metal-Insulator-Metal Waveguides Coupled with Resonators.

A surface plasmon polariton refractive index sensor based on Fano resonances in metal–insulator–metal (MIM) waveguides coupled with rectangular and ring resonators is proposed and numerically investigated using a finite element method. Fano resonances are observed in the transmission spectra, which result from the coupling between the narrow-band spectral response in the ring resonator and the broadband spectral response in the rectangular resonator. Results are analyzed using coupled-mode theory based on transmission line theory. The coupled mode theory is employed to explain the Fano resonance effect, and the analytical result is in good agreement with the simulation result. The results show that with an increase in the refractive index of the fill dielectric material in the slot of the system, the Fano resonance peak exhibits a remarkable red shift, and the highest value of sensitivity (S) is 1125 nm/RIU, RIU means refractive index unit. Furthermore, the coupled MIM waveguide structure can be integrated with other photonic devices at the chip scale. The results can provide a guide for future applications of this structure.