Multilayer Waveguide Structure Research Articles

Enhanced detection accuracy and signal-to-noise ratio of surface plasmon resonance based refractive index sensor with the addition of thicker layer of Silicon

The improvement in the sensitivity performance of conventional surface plasmon resonance (SPR) based sensors with the addition of thin layers of various high index dielectrics (e.g. 5 nm–10 nm of Silicon) is well established. This improvement in sensitivity comes at a price of reduced detection accuracy, deteriorated signal-to-noise ratio (SNR) and small value of Figure of Merit (FOM). Sensors with high detection accuracy and SNR find applications in the direct detection of small molecular (few hundreds of Daltons) interactions or low molecular concentrations (physiological concentration) on the surface of the sensor. The current paper presents design methodology and theoretical analysis of the performance of SPR based refractive index sensor with enhanced SNR, detection accuracy, and FOM attained when a thicker layer of Silicon (60 nm–400 nm thickness) is introduced in the conventional Kretschmann configuration employing angular interrogation technique. The analysis is valid for any high index dielectric layer that is used to enhance the electromagnetic field associated with the surface plasmon (SP) mode excited at the metal-dielectric interface. In the present paper, we show that the SP mode which participates in the sensing applications can be excited at the metal-dielectric interface for multiple thicknesses of Silicon. Analytical expressions are derived to compute the multiple thicknesses of Silicon using a modal analysis as well as the transfer matrix method (TMM) by considering the SPR sensor as a multi-layered optical waveguide structure. The refractive index SPR sensor with thicker silicon layer is shown to exhibit a long propagation length and large penetration depth in the analyte region, resulting in a higher depth-to-width ratio (defined as the SNR) and detection accuracy in its SPR reflectivity spectrum, hence enhancing the measurement precision of the sensor.

A Study of the Field of View Performance for Full-Color Waveguide Displays Based on Polarization Volume Gratings

Multilayer waveguide structures can realize full-color AR displays of diffractive waveguides. This paper discusses the field-of-view characteristics of a waveguide system with a multilayer structure when polarization volume gratings (PVG) are applied as couplers to achieve a full-color display. The effects of the refractive index and period parameter of PVG-couplers on the field of view are investigated. In addition, a PVG waveguide sample with an optimized design is prepared. The experimental results show that the designed waveguide system can achieve a full-color AR display with a 45° diagonal field of view, which verifies the feasibility of the design and provides a potential solution for AR color waveguide display applications.

Analytical and Numerical Analyses of Multilayer Photonic Metamaterial Slab Optical Waveguide Structures with Kerr-Type Nonlinear Cladding and Substrate

In this paper, we propose the analytical and numerical analyses of multilayer photonic metamaterial slab optical waveguide structures with Kerr-type nonlinear cladding and substrate. The multiple-quantum-well (MQW) photonic metamaterial optical waveguide structure with Kerr-type nonlinear cladding and substrate was also analyzed. We can use the proposed method to study the multilayer optical metamaterial slab optical waveguide structure with the linear cladding and substrate.

On-Fiber Multiparameter Sensor Based on Guided-Wave Surface Plasmon Resonances

We report an ultracompact on-fiber multiparameter sensor that employs multiple guided-wave surface plasmon resonances (GWSPRs) and machine learning based signal processing. The sensor structure entails a gold plasmonic crystal cavity covered with a planar dielectric waveguide on the end-face of a single-mode fiber. Incident light on the gold gratings of the plasmonic crystal cavity excites surface plasmon resonances, which are coupled into the waveguide and induce multiple, high-Q GWSPRs. Due to the difference in the field distributions of these resonance modes, the resonance dips in the sensor reflection spectrum have distinctive responses to external stimuli, which enables simultaneous measurement of multiple parameters. To enhance the sensing accuracy, a neural network model is used to demodulate the sensor responses. A proof-of-concept sensor using a UV-curable polymer as a waveguide material is demonstrated for simultaneous measurement of temperature and salinity of salt solutions. Although we only demonstrate the measurement of two parameters, the proposed sensor has the capability to measure more parameters if a multilayer waveguide structure made of different functional materials is used. The proposed sensor can benefit multifunctional analysis in a broad range of biological, chemical, and environmental monitoring applications.

Fano Resonance Hybrid Waveguide-Coupled Plasmonic Sensor Using Transparent Conductive Oxide in the Near-Infrared Range

We proposed an ultra-sensitive refractive index sensor by using indium-doped cadmium oxide as a plasmonic material operating in near-infrared based on Fano resonance. The proposed sensor has a hybrid multilayer waveguide structure that supports both a long-range surface plasmon polariton (LRSPP) mode and a dielectric waveguide (DWG) mode. The design strategy of the structure parameters of the inner layers is elaborated in detail through the numerical analysis of the two modes. By suitably tailoring the thickness of the coupling layer, a strong mode coupling between the two modes could be achieved, leading to a sharp asymmetric Fano resonance. With the designed optimal physical parameters, our proposed sensor could achieve a maximum intensity sensitivity of 19,909 RIU−1, a 193-fold enhancement than that of a conventional long-range SPR (LRSPR) based scheme. The proposed design can be a promising platform for biochemical sensing in the near-infrared region.

Research on sensing characteristics of diamond multilayer waveguide structure racetrack micro-ring resonator

A racetrack micro-ring resonant cavity sensor based on the diamond's material is proposed in this paper. In the model, the vertical-section of the waveguide adopts a five-layer ridge-type waveguide structure based on CH3NH3PbI3, SiO2 and diamond, i.e. CH3NH3PbI3-SiO2-Diamond-SiO2-CH3NH3PbI3. First, on the basis of the resonant principle and coupled mode theory, this study investigated the light field intensity distribution characteristics of the integral resonant cavity, the longitudinal section of a single straight waveguide, the racetrack micro-ring, and the longitudinal section of the straight waveguide by using the finite element method in COMSOL. The analysis shows that the introduction of CH3NH3PbI3 as an isolation layer can avoid the light scattering loss and leakage loss, and significantly enhance the filtering performance. In addition the sensing characteristics of the Add-drop racetrack resonator were further studied. Results showed that the structure could achieve a quality factor of 105, and the sensitivity could reach 14833.33 dB/RIU. In the detection system with a signal-to-noise ratio of 30 dB, the detection limit was 2.02 × 10−7 RIU. Compared with the traditional All-pass single micro-ring resonator, the proposed structure shows advantages of high tenability, high sensitivity and low detection limit.

Theoretical Analysis of On-Chip Vertical Hybrid Plasmonic Nanograting

A complementary metal oxide semiconductor (CMOS) compatible photonic-plasmonic waveguide with nanoscale dimensions and better optical confinement has been proposed for the infrared (IR)–band applications. The design is based on the multi-layer hybrid plasmonic waveguide (Si–SiO2–Au) structure. The 3D-finite element method (FEM)–based numerical simulations of single slot hybrid plasmonic waveguide (HPWG) confirms 2.5 dB/cm propagation loss and 15 μm−2 confined intensity. Moreover, its application as dual-slot nanograting is studied with higher propagation length and ultra–low–dispersion near the 1550–nm wavelength. The proposed low-dispersion nanoscale grating design is suitable for future lab–on–chip nanophotonic integrated circuits.

Ultra-narrowband absorption filter based on a multilayer waveguide structure.

We propose a six-layer waveguide structure embedded in a single-layer grating based on guided-mode resonance (GMR), which can realize ultra-narrowband filtering with a tunable resonance wavelength. The filtering characteristics were analyzed and calculated by rigorous coupled-wave analysis (RCWA) and COMSOL Multiphysics. The narrowband resonance wavelength and absorption are tuned by changing the geometry and physical parameters of the structure such as the grating period and width, layer thickness, and materials. We designed and calculated the full width at half maximum (FWHM) and resonance absorption spectra in detail under different polarization states of electromagnetic waves. We obtained an absorption FWHM of 8.51e-5 nm for the transverse electric (TE) mode and 0.023 nm for the transverse magnetic (TM) mode, with the absorption coefficients having a value over 99.2%. The GMR filtering structure shows a good sensitivity and figure of merit (FOM) for refractive index sensing. For instance, a very high FOM of 17782.6/RIU for TM incidence is observed. These structures can have possible applications in optical information devices and sensors.

A general method for analyzing arbitrary planar negative-refractive-index multilayer slab optical waveguide structures

In this paper, a general method for analyzing arbitrary planar negative-refractive-index (NRI) multilayer slab optical waveguide structures was proposed. Some degenerated examples were introduced to prove the accuracy of the proposed method. The analytical and numerical results show excellent agreement. The method can also be degenerated to analyze arbitrary planar conventional optical waveguide structures. Based on this general method, the analysis and calculation of any kinds of planar NRI slab optical waveguide structures and planar conventional optical waveguide structures can be achieved easily.

Simulation study of multilayer hybrid plasmonic switch using Franz–Keldysh effect

A CMOS compatible three-port all-optical silicon switch working in 1.473 to 1.502 μm (extinction ratio ( ER ) = 5.5 dB, λC = 1.488 μm) and 1.512 to 1.5306 μm (ER = 3.079 dB, λC = 1.52 μm) bands is demonstrated in this work through numerical simulations. However, in spite of the all optical control, having null refractive index contrast between the transmitting and control waveguides of the switch causes the switching merit to deteriorate because of light leaking from the transmitting waveguide. Later, by employing Franz–Keldysh effect-induced absorption coefficient tuning of Si1 − x Gex (x = 0.85) to replace the silicon control port of the switch, 2.95-dB leakage reduction in the ON state is achieved, which is assessed in detail. Also, our numerical simulations confirmed the bandwidth of 38 GHz, which suggested a multilayer plasmonic waveguide structure.

Computational analysis of metamaterial–aluminum–silicon solar cell model

In this paper, the optical parameters of an improved waveguide structure for a more efficient silicon solar cell are studied. Despite its favorable electronic, physical, and chemical properties, silicon remains a poor absorber of light. The optical losses due to the reflection at the air/glass interface of the cell and the transmission at its back are other factors, which limit the cell conversion efficiency. Consequently, several mechanisms for light trapping capable to increase the collection of the incident photons as electrical current and to decrease the transmission loss, have been developed. In this context, we propose a multilayer waveguide structure in which the sunlight is guided by a metamaterial layer and the transmission loss is eliminated by an aluminum back reflector. The reflection and transmission coefficients are derived by using the Generalized Transfer Matrix Method. The application of the law of conservation of energy allowed the determination of the absorption coefficient. These optical parameters are examined for several angles of incidence for s-polarized light, p-polarized light and unpolarized light. Simulation results show a significant reduction of reflection and a complete suppression of transmission.

Novel Ridge-Type Gold Film Waveguide for Surface Plasmon Polariton Laser

Surface plasmon polariton lasers are the basis for photonic circuits, but their losses, thresholds, and some other problems remain thorny issues. In this study, we put forward a novel ridge-type gold film surface plasmon polariton laser. The device adopts a multi-layer hybrid waveguide structure, where the bottom layer is a gold film, and a gold ridge is formed over the center of the gold film. We symmetrically place the two SiO2layers on both sides of the gold ridge as buffer layers and deposit a gold nanoribbon on the top of gold ridge. Two air gaps are formed between the gold ridge and SiO2buffer layers. We numerically study the structure, and the results show that at the operating wavelength of 1550 nm, the effective mode area reaches 1.375 × 10−5λ2 , and the confinement factor reaches 0.75. When the width of the SiO2layer is 2 nm, the height of the ridge is 10 nm, and the angle of the ridge is 80°, the waveguide can effectively enhance the light field confinement so as to limit the energy to a very small range and exhibits the minimum gain threshold. The waveguide can provide a solution for the optical source device of the surface plasma excitation circuits and has great application potential in the ultra-small and high-density optical chips.

Tailoring the Structure of Multilayered Hybrid Silicon Vertical Waveguide to Achieve Anomalous Dispersion

In order to decrease the dispersion of the silicon vertical slot waveguide, we propose a multilayered hybrid silicon vertical waveguide structure. This multilayered waveguide is formed by three low-refractive-index regions interleaved with two narrow silicon rails. Simulation shows that the optical field in the central low-index region is enhanced. After optimization, the dispersion of the waveguide can be limited within ±300 ps/nm/km from 1450 to 1950 nm. This multilayered waveguide has potential in on-chip nonlinear optical applications, such as in all-optical signal processing.

Analyzing the multilayer metamaterial waveguide structure with the Kerr-type nonlinear cladding

A general method for analyzing the multilayer metamaterial optical waveguides with the Kerr-type nonlinear cladding was proposed. To prove the accuracy of the proposed general method, a degenerated example was introduced. The analytical and numerical results show excellent agreement. The similar process can also be used to analyze TM waves propagating in the multilayer metamaterial waveguide structure with the Kerr-type nonlinear cladding.

Simulation analysis of micro-ring resonator based on diamond multilayer waveguide structure

With the development of the technology for fabricating high-quality synthetic diamond and diamond waveguide structures, more and more researchers are being involved in exploring the particular optical properties of diamond for different applications. Because of its high refractive index and nontoxicity to biological species, diamond can be used to make micro-ring resonator to detect the concentration of liquid or gas. In this paper, a single micro-ring resonator model with diamond serving as the core layer is proposed. In the model, the vertical-section of the waveguide adopts a five-layer ridge-type waveguide structure based on As2S3, SiO2 and diamond, i.e. As2S3-SiO2-Diamond-SiO2-As2S3. To investigate the optical properties of the resonator, the vertical-section of the single straight waveguide, the coupling region of the direct waveguide, and the ring waveguide are simulated with the adopted operating wavelength =1550 nm based on the coupling mode theory and micro-ring resonance theory. In addition, the distribution of the field strength for the micro-ring is described at a resonant wavelength of 1543 nm. It is very important to explore the field intensity distribution of the micro-ring for understanding how the light transmits. The transmission characteristics of the micro-ring with the change of the distance between the straight waveguide and the ring waveguide in the coupling region are also simulated. The quality factor and the influence of the coupling coefficient change on the output spectrum are studied by the transfer matrix method and the micro-ring loss is discussed. It is shown that the micro-ring resonator designed with the diamond material has good transmission characteristics. When the resonant wavelength is 1543 nm, the resonant peak reaches more than -12 dB. The quality factor is about 1.54105. When the coupling coefficient k is 0.01, the free spectral range is about 40 nm. The coupling coefficient k is determined by the distance S of the coupling region. The results show that when S is equal to 50 nm, the output spectrum has a good extinction ratio and is better compared with the other values. The error of material processing is mainly affected by size, so the output spectrum near the distance S=50 nm is studied. The result shows that in the tiny change scope, the spectral output peak is linearly related to S. The structure we suggested in this paper expands the application scope of diamond in the field of optics, and provides some guiding significance for developing the optical integrated chips.

Magnetically-Controlled Logic Gates of Graphene Plasmons Based on Non-Reciprocal Coupling

In this paper, we propose magnetically-controlled logic gates of graphene plasmons based on non-reciprocal coupling within the multilayer graphene waveguide structure. The magnetooptical effect of semiconductor substrate leads to the difference in modal indices of graphene plasmons in opposite directions and non-reciprocal coupling, which is investigated by both coupled mode theory (CMT) and finite elements methods (FEM). Such a mechanism enables the design of magnetically- controlled not logic gate, whose output logic can be inversed by reversing the plasmons propagation directions. Furthermore, according to the Boolean algebra, we design two functional logic gates performing as or ( and ) logic gates for one direction of input plasmons, while nand ( nor ) logic gates for the reversed input direction. Minimum extinction ratios as 13.6 or 17.5 dB can be obtained for or ( nand ) or and ( nor ) logic gate. The proposed magnetically-controlled logic gates may provide new inspiration to non-reciprocal graphene plasmons devices.

Multilayer Hybrid Waveguide Amplifier for Three-Dimension Photonic Integrated Circuit

In this letter, a multilayer hybrid waveguide that can be applied to compensate the loss of three-dimension photonic integrated circuit is designed. The multilayer waveguide structure consists of grade index ion-exchange Er3+–Yb3+ co-doped phosphate planar waveguide, step index polymer rectangular waveguide, and heating electrode. Er3+–Yb3+ co-doped phosphate layer is to provide stable amplification performance. Polymer waveguides are designed to control the optical field distribution. The operating temperature is adjusted using the heating electrode. The optical field of signal light and pump light of the hybrid structure is simulated by finite difference method. The six-level model is introduced to calculate the gain characteristic of the hybrid waveguide amplifier with different Er3+ concentrations and operating temperatures. The optimized gain of the hybrid structure can be up to 4 dB/cm with the signal power of 0.1 mW and pump power of 200 mW. This hybrid waveguide can be used in the loss compensation and tunable vertical power splitter area.

A Microring Temperature Sensor Based on the Surface Plasmon Wave

A structure of microring sensor suitable for temperature measurement based on the surface plasmon wave is put forward in this paper. The sensor uses surface plasmon multilayer waveguiding structure in the vertical direction and U-shaped microring structure in the horizontal direction and utilizes SOI as the thermal material. The transfer function derivation of the structure of surface plasmon microring sensor is according to the transfer matrix method. While the change of refractive index of Si is caused by the change of ambient temperature, the effective refractive index of the multilayer waveguiding structure is changed, resulting in the drifting of the sensor output spectrum. This paper focuses on the transmission characteristics of multilayer waveguide structure and the impact on the output spectrum caused by refractive index changes in temperature parts. According to the calculation and simulation, the transmission performance of the structure is stable and the sensitivity is good. The resonance wavelength shift can reach 0.007 μm when the temperature is increased by 100 k and FSR can reach about 60 nm. This structure achieves a high sensitivity in the temperature sense taking into account a wide range of filter frequency selections, providing a theoretical basis for the preparation of microoptics.

Forward and backward wave propagation in multilayer planar waveguide using metamaterials layer

In this study, an efficient method is discussed to analyze the multilayer planar waveguides with double negative guided (DNG) and double positive material as guiding film. Here, among various lossless multilayer planar waveguide structures, only three layer and five layer structures are discussed. For these structures, guided dispersion characteristic, along with electric field distribution of TM modes are numerically analyzed and compared. This analysis enables an effective comparison of guided modal properties of various modes and results in a better understanding of the multilayer planar waveguide with DNG as guiding film.

Investigation of multilayer, periodic, multistrip, and multislot waveguiding structures

For complex planer periodic structures, a system of spectral-domain integral equations is obtained. The unknowns in the equations are the coefficients of 2D Fourier transforms of the current density on strips and the tangential electric fields in slots. The number of dielectric layers, strips, and slots is not bounded. The system is solved by means of the Galerkin method with a basis taking into account the edge singularity. The singular (static) component of the kernel is separated and analytically transformed.