Hybrid Slot Research Articles

Reversed self-steepening in Si3N4-organic hybrid slot waveguides with engineered nonlinearity

Abstract Dispersion of nonlinearity greatly influences both temporal and spectral evolutions for ultrashort pulses, although difficult to be tailored in a wide spectral range. Here, we show the hardly observable reversed self-steepening in an on-chip Si3N4-organic hybrid slot waveguide with sophisticated dispersion and an increased nonlinear coefficient with wavelength. An octave-spanning supercontinuum with significant red-shift spectral broadening and a rectangle-shaped pulse waveform with a sharp rising edge of 13 fs can be generated. We study the robustness of reversed self-steepening under different operating conditions and reveal its nonlinear dynamics. This deepens the understanding on the dispersion of nonlinearity and helps develop novel nonlinearity-engineered devices for on-chip optical shock formation, pulse shaping, and signal processing in the future.

Performance assessment and optimization of three-dimensional hybrid slot–effusion jet cooling configuration of an annular combustor liner

In this study, the film cooling performance of a three-dimensional (3D) hybrid slot–effusion configuration and its advantages over a baseline pure 3D slot cooling are investigated in detail using both experimental and numerical investigations. The numerical model is validated by in-house experiments conducted on a hybrid cooling configuration with a 3D slot and staggered effusion array. Infrared thermography and hot wire anemometry are used in this study to analyze the thermal and flow fields. The cooling performance of pure 3D slot and hybrid configurations is compared under identical coolant consumption. The coolant mass flow ratio (MFR) determines the cooling behavior in hybrid cooling. At low MFRs, hybrid cooling is less effective than pure 3D slot cooling. In addition, it is observed that there exists an optimal MFR where hybrid cooling outperforms 3D slot cooling. Subsequently, the effect of key design variables on the cooling performance of the hybrid configuration is studied, and they are optimized at typical combustor operating conditions using a genetic algorithm coupled to a Kriging surrogate model. The optimal configuration is experimentally tested at laboratory conditions and compared with the baseline 3D slot configuration, and it is noted that there is a significant improvement in the cooling effectiveness. Additionally, the film cooling performance of the optimized configuration at combustor representative operating conditions of maximum BR of 2 shows an enhancement of 16% in area-averaged adiabatic effectiveness and a 60% reduction in the standard deviation of local adiabatic effectiveness as compared to the baseline 3D slot cooling.

A hybrid slot jet impingement/microchannel heat sink for cooling high-power electronic devices: A combined experimental and numerical study

Jet impingement cooling and microchannel cooling have been extensively adopted as the efficient cooling technologies in the thermal management of high-power electronics. In this research, an optimal hybrid slot jet impingement/microchannel heat sink, integrating the merits of two cooling methods, obtained from multi-objective optimization is machined and tested experimentally. By varying test conditions, the impact of inlet mass flow rate, inlet temperature and heat flux variations on the flow resistance and heat removal capacity of the optimal heat sink are investigated. Moreover, by conducting overall 3D numerical simulation, the internal flow and heat transfer behaviours of the heat sink are also investigated. By analyzing the flow field inside the heat sink, the experimental phenomena are interpreted. Comparing the relative errors between the numerical simulation and experimental measurement values under the same working conditions, it could be observed that the maximum relative error of the pressure drop is about 9.7 %, and the maximum relative error of the average temperature of the heated surface is only 0.9 %. According to the experimental results, as the heat flux is 200 W/cm2, the inlet temperature is 293 K and the inlet mass flow rate is 28 g/s, the average temperature of the heated surface does not surpass 348 K, while the pressure drop is only 2.46 kPa. Additionally, compared with the literature results, the hybrid heat sink obtained after multi-objective optimization in this study realizes a significant enhancement in cooling capacity, while the pumping power to heating power ratio is not significantly increased.

Design of a High-Gain Hybrid Slot Antenna Array Based on Bulk Silicon MEMS Process for W-Band Applications

A W-band, high-gain, hybrid slot antenna array based on bulk silicon MEMS technology is proposed in this paper. The high-order-mode cavity is explored to excite the 2 × 2-slot basic unit, so as to reach the low-profile requirement of the bulk silicon MEMS process. To avoid the fragile structure of the large-scale antenna arrays based on the bulk silicon MEMS process, the ridge gap waveguide is employed to build the feed network for a large-scale array. A vertical transition between a rectangular waveguide and a ridge gap waveguide is designed to support the low-loss and low-cost assembling method between the radiation units and the feed network. An 8 × 8-slot hybrid antenna array is simulated and fabricated. The measured results show a relative bandwidth (VSWR < 2) of 8.1% with the first side-lobe level less than −11 dB over the frequency band of 91–97 GHz. A maximum gain of 26.1 dBi with the radiation efficiency of 65.2% is achieved. With high gain and high fabrication efficiency, the proposed hybrid slot antenna array would be valuable for W-band radar applications.

Fabrication and characterization of electro-optic polymer/silicon hybrid MZI for interrogating small signals from an ECG

A Mach–Zehnder interferometer (MZI) composed of electro-optical polymer/silicon hybrid slot waveguides is reported. The device is designed to be asymmetrical so that the modulator is in a linear workspace when no electric field is applied to the initial operating state. We rely on the fast and strong nonlinearities of CLD-1/PMMA that infiltrates silicon rather than on the slower free-carrier effect in silicon. The modulated arm waveguides are designed in the shape of silicon/polymer hybrid slot waveguides to increase the interaction of the polymer material with the light field. The results show that the loss of the proposed MZI is 3.51 dB with a core size of 420μm × 160μm, and the half-wave voltage of the MZI is 2.1 V at 1550 nm, which provides the possibility of application in measuring small signals from an electrocardiogram with the optical principle.

Optimal parameter design of a slot jet impingement/microchannel heat sink base on multi-objective optimization algorithm

Jet impingement and microchannel cooling as effective cooling methods have been widely employed for thermal management of high heat flux electronics. In this work, a novel hybrid slot jet impingement/microchannel heat sink, combining the advantages of two cooling technologies, was proposed to achieve vertical flushing of the jet and timely discharge of the waste fluid. To further enhance the cooling performance, a 3-D numerical simulation was applied to evaluate the impact of inlet and outlet branch passage inclination ratios (Hin,1/Hin,2 and Hout,1/Hout,2), channel unit width (W1), channel width ratio (φ) and channel height (H3) on heat sink thermal-hydraulic characteristics. According to the parametric analysis, the variations in the inlet and outlet branch passage inclination ratios have significant effect on the mass flow distribution among the heat transfer channels. Afterward, to acquire the optimal compromise solution for practical applications, the artificial neural network training and multi-objective optimization algorithms, i.e. multi-objective particle swarm optimization (MOPSO) and multi-objective genetic algorithm (MOGA), are utilized to optimize the geometrical parameters, i.e. W1, φ and H3. During the optimization, the average heated surface temperature (T¯heat) and the total pressure drop (ΔP) are two conflicting objectives to evaluate the heat transfer and resistance characteristics. Finally, an optimal compromise solution (W1=1.03mm, φ=0.58 and H3=2.44mm) is chosen from the Pareto front by using the classical decision-making algorithm, i.e. TOPSIS. Compared with one objective minimization in the Pareto front, the optimal compromise solution has a sound balance between heat transfer and resistance performance. Additionally, for the optimal compromise solution, with an inlet velocity of 1.5 m/s and a heat flux of 200 W/cm2, the maximum and average temperature of the heated surface does not exceed 73 °C and 67 °C, respectively, and the total pressure drop is only 5.7 kPa.

Nanophotonic Ring Resonator Based on Slotted Hybrid Plasmonic Waveguide for Biochemical Sensing

Hybrid plasmonic waveguide (HPW) holds great promise as a potential nanophotonic platform for a variety of applications including biosensing which usually requires strong analyte–matter interaction. We propose a nanophotonic ring resonator based on a slotted HPW (SHPW) as a platform to realize resonance-enhanced sensing with strong light–analyte interaction on a subwavelength scale. The optical mode guided in the bus waveguide gets coupled to the slotted ring as a hybrid plasmonic (HP) mode which enables efficient bio-sensing. The SHPW utilized in the ring provides a larger propagation length of over 2.5 mm with subwavelength confinement at the wavelength of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.55 \mu \text{m}$ </tex-math></inline-formula> . The slotted structure also exhibits broadband propagation of HP where the propagation length remains around 1.2 mm over a wavelength range from 1.3 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.6 \mu \text{m}$ </tex-math></inline-formula> . A 29.6-nm shift in the transmission spectra of the engineered ring resonator is observed on changing the analyte refractive index to 1.3514 (polluted water) from 1.333 (pure water). The sensitivity for the detection of polluted water is reported to be 1609 nm/RIU, which is approximately four times more than the dielectric slotted ring resonator and eight times more than the ring resonator with a ridge structure. The proposed engineered slotted waveguide structure may be helpful in realizing nanophotonic devices for various applications, including biochemical sensing and large-scale photonic integration.

TE-Pass/TM-Stop On-Chip Mach-Zehnder interferometer with high phase sensitivity

Mach-Zehnder interferometer (MZI) has attracted intense research interest due to the extensive applications in optical integrated systems. This paper presents a TE-Pass/TM-Stop graphene-based on-chip MZI, including splitter, phase shift arm, reference arm and combiner. The splitter and combiner are based on subwavelength gratings (SWGs) coupler. Hybrid slot waveguides with photonic crystals (PhC) are adopted as the phase shift arm and the reference arm, with and without graphene, respectively. The results show that the phase sensitivity is 1010 rad/RIU-cm at 1.55 μm, which is 10 times higher than the strip waveguide-based graphene MZI.

Ultra-compact and highly sensitive refractive index sensor based on a chalcogenide suspended slot hybrid plasmonic microring resonator

A microring resonator based on chalcogenide suspended slot hybrid plasmonic waveguide (CSSHPW) is designed for the refractive index (RI) sensing. The CSSHPW consists of a suspended Si nanowire with a nanoscale air gap and a Cu film deposited on a chalcogenide support layer. The mode characteristics of the suspended slot hybrid plasmonic mode (SSHPM) in the CSSHPW are simulated by using the finite element method (FEM). The simulation results show that the waveguide sensitivity (Swg) as high as 0.8 and the optical propagation loss as low as 0.08 dB/µm are obtained by optimizing the structure. The RI sensitivity (S), detection limit (DL), and detection range (DR) of the CSSHPW-based microring resonator (MRR) with a radius of 2 µm are 511.5 nm/RIU, 4.72 × 10−5 RIU, and 0.158 RIU, respectively. These superior performances as well as the fully complementary metal-oxide-semiconductor (CMOS) compatibility pave the way for CSSHPW-based biochemical sensors to realize on-chip high-S waveguide sensors. Moreover, the CSSHPW-MRR has a small size, high modulation depth, large Swg, and Cu cap of easy electrode formation, it facilitates the fabrication of a high-performance electro-optic (EO) modulator by infilling the slot with EO material.

Photodetector Based on Twisted Bilayer Graphene/Silicon Hybrid Slot Waveguide with High Responsivity and Large Bandwidth

Graphene/silicon hybrid photodetector operating at communication wavelength has attracted enormous attention recently due to its potential to realize bandwidth larger than 100 GHz. However, the responsivity is intrinsically limited by the low absorption from the atomic-thick graphene monolayer, which imposes significant obstacles towards its practical application. Although plasmonic structures has been widely applied to enhance the responsivity, it may induce the metallic absorption thus limit the responsivity lower than 0.6 A/W. Twisted bilayer graphene (TBG) has been reported to hold the ability to dramatically enhance the optical absorption due to the unique twist-angle-dependent van Hove singularities. In this article, we present a design of a silicon/TBG hybrid photodetector with a responsivity higher than 1 A/W and bandwidth exceeding 100 GHz. The enhanced responsivity is achieved by tuning the twisted angle of TBG to increase the absorption within the 1550 nm as well as utilizing the silicon slot waveguide to boost the mode overlap with TBG. The fabrication process of proposed design is also discussed demonstrating the advantages of low fabrication complexity. The proposed silicon/TBG photodetector could not only exhibit superior performance compared to previously reported silicon/monolayer graphene photodetector, but also pave the way for the practical application of graphene-based silicon optoelectronic devices.

Active pressure and flow rate control of alkaline water electrolyzer based on wind power prediction and 100% energy utilization in off-grid wind-hydrogen coupling system

To increase the energy-conversion efficiency while maintaining safety in commercial alkaline water electrolyzer (AWE) systems. In this paper, (1) a 4 kW AWE system test is conducted to study the effect of pressure, temperature and lye flow rate on the hydrogen in oxygen (HTO) and voltage. (2) The mechanism of HTO is analyzed, and this paper first presents the steady-state and dynamic HTO model in AWE system with physical porous separator. Meantime, the voltage and HTO model are developed and calibrated by the steady-state and transient operation conditions, and relative errors are within 5 %. (3) Based on the analysis of the pressure and lye flow rate on HTO, it is important to obtain the optimal pressure-current density change trends, with an extension of the AWE system’s minimum load from 20 % by the traditional constant pressure controller to 11.78 % by the pressure controller and 8.95 % by the pressure and lye flow rate control, and its corresponding current density is 0.0264 A/cm2 and 0.0196 A/cm2, respectively. (4) Both the multi-AWE configuration and alkaline water electrolyzer couples with battery could complete 100 % utilization of wind power. Therefore, the controlling methods is a great way of lowering load limit of AWE and cutting the start-stop times under renewable energy conditions, besides, the controlling methods and multi slot hybrid mode can achieve 100 % energy utilization in hydrogen production scenario of wind power network.

Polarization-Insensitive Graphene Modulator Based on Hybrid Plasmonic Waveguide

A polarization-insensitive graphene-assisted electro-optic modulator is proposed. The orthogonal T-shaped metal slot hybrid plasmonic waveguide allows the polarization-independent propagation of transverse electric field mode and complex mode. By the introduction of dual-layer graphene on the ridge waveguide, the polarization-insensitive modulation depths of the TE mode and complex mode are 0.511 dB/µm and 0.502 dB/µm, respectively. The 3 dB bandwidth of the modulator we have proposed is about 127 GHz at the waveguide length of 20 μm. The power consumption of 72 fJ/bit promised potential graphene electro-optic modulator applications for on-chip interconnected information transfer and processing.

Hybrid nano-jet impingement cooling of a curved elastic hot surface under the combined effects of non-uniform magnetic field and upper plate inclination

In this study, slot hybrid nano-jet impingement cooling application of a curved elastic surface is considered under the combined effects of non-uniform magnetic field and upper plate inclinations. When magnetic field is present, the local Nusselt number (Nu) peaks are suppressed, but in absence of magnetic field, profound rise of stagnation point Nu is seen with higher Re. The increment amount of the local peak Nu becomes 155.5% and 50.5% at Ha=0 and Ha=20. Significant variations of the local peak Nu locations are obtained when elastic modulus are varied with magnetic field at the highest strength. There is 141% variation of average Nu for the curved elastic part when walls with the lowest and highest elastic modulus cases are compared. There is 7% variations in the average Nu when the amplitude of the magnetic field is varied. The left and right plate inclinations contributed differently to the overall convective cooling performance due to the non-uniform magnetic field effects. Non-uniform magnetic field parameters along with the plate inclinations can be used for cooling performance of confined slot jet impingement system for a surface with curved elastic part.

A Duplexing Hybrid Slot Antenna Design With High Isolation for Short-Range Radar Detection and Identification Applications at 24 GHz Band

This paper presents a duplexing hybrid antenna architecture for short-range radar systems with high isolation and low loss between the two transmitting (TX) and receiving (RX) ports. The antenna utilizes a single slot for common resonance shared by the two TX and RX port excitations. These two ports were constructed through two parallel microstrip lines crossing over the specified shaped slot. The feeding structures of these two microstrip feedings and the separation are optimally designed to ensure the mutual coupling signals out-of-phase, and therefore the signal cancellation can be achieved, leading to a high isolation between these two ports. In this design, the slot length is 0.92λ at 24.125 GHz, forming an equivalent short circuit at the other port. Given the initial design criteria, the design with the optimal isolation could readily be found by minimal full-wave simulations. Meanwhile, the equivalent circuit model was used to investigate the working principles and to improve the isolation bandwidth and impedance matching at the central frequency. The measured maximum isolation is 70 dB at 24.125 GHz. The RF front-end modules with TX and RX amplifiers are also integrated to validate its feasibility for the radar system application. The mechanisms to widen the isolation bandwidth are also addressed.

Dot and Slot Hybridization of Purified RNA.

Dot blotting and slot blotting are techniques for immobilizing several preparations of nucleic acids on the same solid support, usually a charged nylon membrane. The concentrations of the target sequence of interest can be estimated by hybridizing the immobilized samples to an appropriate probe. The amounts of target sequence are estimated by comparing the intensity of signals emitted by dots containing the test samples with standards containing known concentrations of the target sequence. This protocol describes the blotting and subsequent hybridization of RNA that has been purified from cells or tissues.

On the Behavior of Self-Triplexing SIW Cavity Backed Antenna With Non-Linear Replicated Hybrid Slot for C and X-Band Applications

In this paper, a substrate integrated waveguide (SIW) based self-triplexing antenna (STA) with non-linear replicated hybrid slot (NLR-HS) is presented. To the author&#x2019;s best knowledge, the concept of NLR is the first of its kind in the literature used for obtaining self-triplexed operation. Initially, the SIW cavity is loaded by a hexagonal slot merged with two rectangular transverse slots that together produce two distinct resonances around 5.23 and 7.50 GHz. The variation in resonant frequencies of both lower and upper frequency bands can be modelled by applying NLR on the hexagonal slot. To achieve the self-triplexing operation, a coaxial probe-fed parasitic hexagonal patch is placed concentrically inside the hexagonal slot. The third resonance is centered around 10.82 GHz and can be modelled with the help of the gap between the hexagonal slot and parasitic patch.To validate the proposed idea, the design is fabricated and experimentally tested. Moreover, the antenna shows a front-to-back ratio (FTBR) better than 25 dB, average isolation of 43 dB and measured gain (efficiency) values of 7.33 (97.39&#x0025;), 6.66 (95.82&#x0025;), and 6.28 (97.83&#x0025;) dBi at three resonances. Good agreement between the simulated and measured results makes the proposed STA a good candidate for practical applications.

Enhanced optical nonlinearity in a silicon–organic hybrid slot waveguide for all-optical signal processing

Silicon photonic integrated devices used for nonlinear optical signal processing play a key role in ultrafast switching, computing, and modern optical communications. However, current devices suffer from limited operation speeds and low conversion efficiencies due to the intrinsically low nonlinear index of silicon. In this paper, we experimentally demonstrate enhanced optical nonlinearity in a silicon–organic hybrid slot waveguide consisting of an ultranarrow slot waveguide coated with a highly nonlinear organic material. The fabricated slot area is as narrow as 45 nm, which is, to the best of our knowledge, the narrowest slot width that has been experimentally reported in silicon slot waveguides. The nonlinear coefficient of the proposed device with a length of 3 mm is measured to be up to 1.43 × 10 6 W − 1 km − 1 . Based on the nanostructure design, the conversion efficiencies of degenerate four-wave mixing showed enhancements of more than 12 dB and 5 dB compared to those measured for an identical device without the organic material and a silicon strip waveguide, respectively. As a proof of concept, all-optical canonical logic units based on the prepared device with two inputs at 40 Gb/s are analyzed. The obtained logic results showed clear temporal waveforms and wide-open eye diagrams with error-free performance, illustrating that our device has great potential for use in high-speed all-optical signal processing and high-performance computing in the nodes and terminals of optical networks.

Hybrid plasmonic slot waveguide with a metallic grating for on-chip biosensing applications.

Designing reliable and compact integrated biosensors with high sensitivity is crucial for lab-on-a-chip applications. We present a bandpass optical filter, as a label-free biosensor, based on a hybrid slot waveguide on the silicon-on-insulator platform. The designed hybrid waveguide consists of a narrow silicon strip, a gap, and a metallic Bragg grating with a phase-shifted cavity. The hybrid waveguide is coupled to a conventional silicon strip waveguide with a taper. The effect of geometrical parameters on the performance of the filter is investigated by 3D finite-difference time-domain simulations. The proposed hybrid waveguide has potential for sensing applications since the optical field is pulled into the gap and outside of the silicon core, thus increasing the modal overlap with the sensing region. This biosensor offers a sensitivity of 270 nm/RIU, while it only occupies a compact footprint of 1.03µm×17.6µm.

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.

Compact hybrid plasmonic slot waveguide sensor with a giant enhancement factor for surface-enhanced Raman scattering application.

In this paper, a surface-enhanced Raman scattering (SERS) sensor with a giant field enhancement factor based on the coupling of surface plasmon polaritons (SPPs) is designed and studied theoretically. The proposed sensor adopts a metal-dielectric layered hybrid slot waveguide structure, combining thin metal (gold) layers and silicon nitride strip waveguides. Unlike other similar sensors, the silicon nitride waveguide structure does not serve as an excitation signal channel, conventionally loaded with the guided modes, but as an auxiliary layer, making it easier to concentrate the light field in the slot. Therefore, the sensor has a higher enhancement factor compared to the pure metal or dielectric slot structure. The results exhibit that we can obtain a maximum enhancement factor exceeding 10^6 under the compact configuration of 510 × 300 × 225nm^3 at the wavelength of 785 nm. By analyzing the dependence of the sensor performance on the structural parameters, we show that the structure of such sensor can directly be applied to SERS spectroscopic analysis as well as integrated with micro-and nano-photonic platform to perform on-chip detection system.