Metal-dielectric Waveguide Research Articles

Miniaturized Design of a 1 × 2 Plasmonic Demultiplexer Based on Metal–Insulator-Metal Waveguide for Telecommunication Wavelengths

In this work, a numerical analysis of a compact 1 × 2 plasmonic demultiplexer based on a metal–insulator-metal (MIM) waveguide is presented. Two hollow circular cavities are side coupled to the bus waveguide on both sides. The cavities are designed in such a way that they resonate at the working wavelength of 1310 nm and 1550 nm. The mechanism of light coupling to an MIM waveguide has not been considered in previous studies. Therefore, a silicon tapered mode converter is integrated with a plasmonic demultiplexer for the efficient conversion of a dielectric to a plasmonic mode. The footprint of the device is 6 μm × 6 μm. The crosstalk at P1 and P2 is ~ 14.07 dB and ~ 13.67 dB for the transmission wavelength of 1310 nm and 1550 nm, respectively.

Highly Sensitive Micro-Opto-Electromechanical Systems Accelerometer Based on MIM Waveguide Wavelength Modulation

In this article, a novel micro-opto-electro- mechanical system (MOEMS) accelerometer sensor based on metal–insulator–metal (MIM) waveguide wavelength modulation is proposed. The device senses the vibration signal of external acceleration by the mechanical sensing system and uses the MIM waveguide in the optical sensing system to sense the displacement of the mechanical vibration component to cause the change of the light wavelength. The characteristics of the optical sensing system and the mechanical sensing system of the MOEMS accelerometer are analyzed by the finite-difference time-domain (FDTD) and finite-element analysis (FEA) methods, respectively. The simulation results show that the proposed accelerometer sensor has an optical system sensitivity of up to 7.827 in the wavelength modulation range of 1– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12~\mu \text{m}$ </tex-math></inline-formula> , a mechanical sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.292963~\mu \text{m}$ </tex-math></inline-formula> /g, a natural frequency of 939.28 Hz, and a linear measurement range of ±4.4 g. Surprisingly, we obtained accelerometer sensitivity up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.293~\mu \text{m}$ </tex-math></inline-formula> /g and resolution up to 436.1 ng ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta \lambda ={1}$ </tex-math></inline-formula> pm). We also show the performance advantages of this accelerometer with high sensitivity and high resolution over the measurement range by comparing this MOEMS accelerometer sensor with previously reported work. Based on these performance characteristics, we expect this work to be widely used in high-precision measurements for inertial navigation.

Metal‐insulator‐metal waveguide‐based plasmonic sensors: Fantasy or truth—A critical review

AbstractThere is a hysteria over plasmonic sensors based on metal‐insulator‐metal (MIM) waveguides and researchers around the globe are extensively studying these devices over the past two decades for diverse sensing applications for instance temperature, refractive index, pressure, and biochemical applications among others. The sensors based on MIM waveguides (WGs) are compact and offer unmatchable sensitivity as assessed with dielectric waveguide‐based sensors along with an extraordinary figure of merits (FOM). However, the major concern is that most of these sensors are only numerically simulated/analyzed and there is no experimental demonstration accessible to date. Therefore, in this mini‐review, these highly alluring sensor designs are critically analyzed to identify if they are practically feasible or just a fantasy among the scientific community.

Hybrid MIM plasmonic waveguide by triangular grooves

This paper introduces a hybrid Metal-Insulator-Metal (MIM) plasmonic waveguide. The proposed MIM waveguide has triangular grooves that are periodically placed along the broad wall. The waveguide is analyzed and simulated in a 3-D model. The results show this structure operates as a suitable filter with high transmission amplitude at operational bandwidth of Hz. This waveguide size is 0.5μm×0.44μm with seven triangular grooves and the track length is 3.35μm. The short track length and a small number of grooves are the main advantages of the proposed waveguide. It has a more acceptable transmission amplitude and compact size compared to the previously reported designs.

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.

Phase-Difference-Dependent Surface Plasmon Polariton Waveguide Coupling in a Symmetrical Dual-Channel Metal-Insulator-Metal Structure

This work reports a phase difference modulated coupling of two surface plasmon polariton (SPP) sources in a symmetrical two-channel metal-insulator-metal (MIM) waveguide device. In the device, two sources with different initial phases interact indirectly through the function of a rectangular cavity. With the phase difference varying, we have achieved tunable SPP coupling followed by continuously adjustable filtering property and Fano resonance. Further results show that the tunable SPP coupling in the resonance cavity can be well described by the electromagnetic wave interference theory. Moreover, we have also demonstrated the excellent performance of this phase-difference-dependent MIM waveguide in refractive-index sensing and have achieved considerable sensitivity as high as 818.8 nm/RIU. This research has great significance for tunable filtering and signal compensation in MIM waveguide-based photonic chips and also provides a device with high potential in refractive-index 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.

Evaluation of the coupling characteristics of a sandwiched plasmonic waveguide between two dielectric waveguides using air-gap couplers to achieve high-performance optical interconnects

To achieve ultrahigh-density nanoplasmonic integrated circuits, low-loss conventional dielectric waveguides (CDWs) are used to transfer light into and out of the metal–dielectric–metal (MDM) plasmonic waveguides. We show that sandwiching the MDM plasmonic waveguide between two CDWs forms a Fabry–Perot cavity-like structure, which causes oscillations in the transmission coupling efficiency (TCE) into the output CDW as the length of the MDM waveguide is increased. Three types of compact air-gap couplers (AGCs) were used at the interface between those two types of waveguides to enhance the coupling efficiency between them. Our simulation results indicate that tapering CDW before it is connected to AGC not only enhances TCE into the output CDW by 9% over a wide spectrum range but also reduces the need for high-precision fabrication techniques to align AGC at the interface. Moreover, we achieved a TCE into the output CDW of 77% optimized for the optical communications wavelength of 1550 nm when the length of the MDM plasmonic waveguide is 600 nm. In addition, we showed that our proposed design has large fabrication tolerance by investigating the change in its spectrum response as various parameters of the design dimensions differ from that of the targeted optimum dimensions. We found that increasing the dimensions of AGC reduces the width of the spectrum, whereas increasing the width of CDW with its tapered part shifts the spectrum to the right by 100 nm per 40 nm increase in the width. We also found that increasing the refractive index of the MDM plasmonic waveguide with AGC controls the cutoff wavelength, in which TCE is almost zero at wavelengths shorter than the cutoff wavelength, and consequently provides a unique advantage in using our proposed design in sensing applications.

Tunable plasmon refractive index sensor and slow light characteristics based on a stub coupled with an ellipse resonator and its derived structure

In this paper, a structure consisting of a stub metal-insulator-metal (MIM) waveguide coupled with an ellipse resonator is proposed. The finite element method (FEM) is used to analyze the transmission characteristics and magnetic field distributions of the structure in detail. The basic structure can support triple Fano resonances. In addition, multi-spectrum characteristics can be achieved by increasing the complexity of the structure. All Fano resonances can be tuned by altering the geometric parameters of the structure. Furthermore, each of the proposed structures has applications in both sensing and slow light devices. The maximum sensitivity of refractive index sensing is up to 1400 nm/RIU. The MIM waveguide structures have potential applications in the field of on-chip optical integration.

Nano-plasmonic refractive index sensor based on metallic slit loaded stub resonator

The combination of optical sensing phenomenon with Nano science is a new paradigm shift in point of care sensing devices. Here, a nano-sensor based on propagating Plasmons is investigated. Due to unique feature of plasmonics having long transmission range and confined the signal beyond diffraction limit, the sensor is designed with metal–insulator-metal (MIM) geometry of plasmonic waveguide. The stub resonator is coupled to MIM waveguide for the desired filter characteristics. The metallic slit is incorporated in the resonating structure and the metallic slit is off-center in resonating structure. The presence of the slit tunes the condition of resonance and Fano interference phenomenon emerges. The device is calibrated according to change in the value of refractive index of analyte and we can observe linear relation between the refractive index of analyte and resonance wavelength. The maximum value of sensitivity is achieved as 1990 nm/ RIU. The proposed geometry may open a new path for nano-sensing based optical chips.

Tunable Multi-Channels Bandpass InGaAsP Plasmonic Filter Using Coupled Arrow Shape Cavities

A new design for a tunable multi-channel plasmonic bandpass filter was numerically investigated using the two-dimensional finite element method (2D-FEM). The proposed multi-channel plasmonic bandpass filter consists of a metal-insulator-metal waveguide (MIM-WG) and double-sided arrow-shaped cavities. Silver (Ag) and a non-linear optical medium (InGaAsP) are used in the designed filter. InGaAsP fills the bus waveguide and arrow-shaped cavities. The refractive index of InGaAsP is sensitive to the incident light intensity, therefore the resonance wavelengths can be controlled. Utilizing different incident light intensities (such as 1017 v2/m2 and 2 × 1017 v2/m2) on the InGaAsP, the filter wavelengths can be tuned over a range from 600 nm to 1200 nm. The proposed filter with a confinement area of 0.5 μm2 can be used in wavelength division multiplexing (WDM), photonic systems, coloring filters, sensing, and 5G+ communication.

Refractive Index Sensor Based on the Fano Resonance in Metal-Insulator-Metal Waveguides Coupled with a Whistle-Shaped Cavity.

A plasmonic refractive index sensor based on surface plasmon polaritons (SPPs) that consist of metal–insulator–metal (MIM) waveguides and a whistle-shaped cavity is proposed. The transmission properties were simulated numerically by using the finite element method. The Fano resonance phenomenon can be observed in their transmission spectra, which is due to the coupling of SPPs between the transmission along the clockwise and anticlockwise directions. The refractive index-sensing properties based on the Fano resonance were investigated by changing the refractive index of the insulator of the MIM waveguide. Modulation of the structural parameters on the Fano resonance and the optics transmission properties of the coupled structure of two MIM waveguides with a whistle-shaped cavity were designed and evaluated. The results of this study will help in the design of new photonic devices and micro-sensors with high sensitivity, and can serve as a guide for future application of this structure.

Design of All-Optical Directional Coupler Using Plasmonic MIM Waveguide for Switching Applications

In this paper, we have proposed, analyzed, and verified the performance of an optimized plasmonic 10-dB directional coupler and a 3-dB directional coupler in 2-D plasmonic waveguides using the finite-difference-time-domain (FDTD) method. A plasmonic 10-dB directional coupler and a 3-dB directional coupler are based on the metal–insulator-metal (MIM) slab waveguide and analyzed at the telecommunication wavelength (λ) of 1550 nm. Here, coupling and transmission characteristics are analyzed with the optimized separation distance between the two parallel waveguides. The developed approach ensures the minimization of the crosstalk and overall directional coupler length via simultaneous adjustment of the separation distance between the parallel waveguide and the length of the linear waveguide. Then, an optimized structure is acquired by trading off between coupling length and separation distance. The proposed 10-dB directional coupler and 3-dB directional coupler feature good energy confinement, ultra-compact, and low propagation loss, which has potential applications in photonic integrated devices, optical signal processors, and other all-optical switching devices.

MIM waveguide system with independently tunable double resonances and its application for two-parameter detection.

A metal-insulator-metal (MIM) waveguide system consisting of a MIM waveguide, a ring cavity, and a semi-ring cavity is proposed. Using the finite element method, the transmission characteristics of the MIM waveguide system are discussed under the different geometry parameters. By detecting the resonance wavelength and varying the refractive index, the sensing performance of the MIM waveguide system is analyzed. The proposed structure can be used as a refractive index sensor with the maximum sensitivity of 2412 nm/RIU. Due to isolating the ring cavity and semi-ring cavity, the independent tuning of double resonances can be realized by changing the refractive index of the insulator in the ring cavity or the semi-ring cavity. Benefiting from two independent refractive index sensing modes, the structure with two isolated resonators can realize the simultaneous measurement of glucose solution concentration and blood plasma concentration. The sensitivity of glucose solution sensing in the ring cavity is 0.13133 nm/(g/L). Meanwhile, the blood plasma concentration detection in the semi-ring cavity is realized with the sensitivity of 0.358 nm/(g/L). The system with two isolated cavities has the potential to be used as an efficient nano sensor, which can achieve simultaneous measurement of two parameters.

Efficient multi-step coupling between Si3N4 waveguides and CMOS plasmonic ferroelectric phase shifters in the O-band.

In this paper we present a thorough simulation-based analysis for the design of multi-step couplers bridging seamlessly plasmonic barium titanate oxide (BTO) ferroelectric phase shifters and thick silicon nitride (Si3N4) waveguides for the O-band. The targeted plasmonic waveguides are a hybrid plasmonic waveguide (HPW) providing low propagation losses and a plasmonic metal-insulator-metal (MIM) slot waveguide offering a high confinement factor for high modulation efficiency. The proposed plasmonic platforms are formed by Copper (Cu) providing CMOS compatibility. The analysis is based on 2D-FD eigenvalue and 3D-FDTD numerical simulations targeting to identify the optimum geometries ensuring the lowest coupling losses, calculated as 1.75dB for the HPW geometry and 1.29dB for the MIM configuration. The corresponding confinement factors are 31.39% and 56.2% for the HPW and MIM waveguides, respectively.

Guided-mode resonance with reduced bandwidth in mid-infrared absorption and thermal emission.

Narrowband resonance plays an important role in many optical applications, especially for the development of wavelength-selective properties and enhanced light-matter interaction. In this paper, we demonstrate metal-insulator-metal (MIM) waveguide gratings, which exhibit guided-mode resonance (GMR) with reduced bandwidth in mid-infrared absorption and thermal emission. Our fabricated MIM waveguide grating consists of a copper substrate, a lossless ZnSe film, and a top gold stripe grating. Our measurements reveal strong GMRs with a bandwidth of 1.29% of the central wavelength in both mid-infrared absorption and thermal emission spectra. By varying structural parameters of the MIM waveguide grating, strong absorptions and thermal emissions of GMRs are observed and tuned within the 3-5 µm wavelength range. These results manifest the great potential of engineering infrared properties by using GMR and could be useful for spectral control in a variety of infrared devices.

Plasmonic band-stop MIM waveguide filter based on bilateral asymmetric equilateral triangular ring

In this paper, a bilateral asymmetric equilateral triangular ring (ETR) band-stop filter based on metal-insulator-metal (MIM) waveguide is proposed. The transmission spectrum and electric field distribution of the filter are simulated and theoretically investigated by finite difference time domain (FDTD) and coupled mode theory (CMT) method. The results show that changing the number and position of resonant cavities can adjust the transmission characteristics of the filter. The minimum transmission and sensitivity of this filter is 0.1% and 1149 nm/RIU, respectively. The filters have broad prospects in the highly integrated optical circuits and refractive index sensor.

Resonance and sensing characteristics of horn-shaped cavity-coupled MIM waveguide

The resonant coupling of optical microcavities to waveguides is important in photonic devices. In this paper, a horn-shaped cavity structure is designed on the side of the metal–dielectric–metal waveguide, and the coupling between the cavity and the waveguide is simulated by the finite-difference time-domain method and the coupled mode theory. It is found that the cavity and local modes appear in the horn-shaped cavity. Second, the geometric parameters of the cavity structure are changed, and the influence of the structural parameters on the transmission spectrum is obtained by theoretical analysis. Third, the maximum refractive index sensitivity of the structure is calculated to be 1750 nm/RIU, and the temperature sensitivity is 2.455 nm/°C. Ultrafine particles are placed between the tips of the horn-shaped cavity structure, and the sensitivity of the wavelength shift of the localized mode and the change in the transmittance of the trapezoidal cavity mode to the particle size and the refractive index of the particles are obtained; the nanoparticle sensor is designed by using this characteristic. The horn-shaped resonator structure proposed in this paper provides a high-performance cavity choice for the design and application of micro-nano sensor devices.

Numerical study on a random plasmonic laser in the metal-insulator-metal structure.

This Letter proposes a random plasmonic laser in the metal-insulator-metal (MIM) structure, in which the dielectric core with gain is dispersed with circular dielectric nanoscatterers. The numerical results from finite-difference time-domain simulation indicate that scattering by the randomly distributed dielectric nanoscatterers in the MIM waveguide provides feedback to the random laser with surface plasmon. The design bypasses the requirement of a distributed feedback structure for the plasmonic waveguide-based nanolasers, which is challenging and expensive in fabrication. Additionally, the MIM structure makes this type of random laser easily applicable to nanoscale integrated photonic devices and circuits.

Theoretical design and analysis of multichannel plasmonic switch based on triangle resonator combined with silver bar

A multichannel plasmonic switch consisted of four metal–insulator–metal (MIM) waveguides and an equilateral triangle resonator (ETR) with a silver bar is proposed. Calculated by coupled mode theory (CMT) and standing wave theory, structural transmittance characteristics are numerically studied by finite difference time domain (FDTD) method. And the results show that the transmission spectrum of the ETR with a silver bar, coupled with a MIM waveguide, can be adjusted by increasing the height and width of the bar. As for the switch, varying with structural parameters of the bar, the transmission spectra in three ports can be tuned by rotating the bar into different angles. And this multichannel plasmonic switch owes a high on/off contrast ratio (R = 36 dB). The proposed switch has potential application value in the area of telecommunication and all-optical signal procession.