Strong Electric Field Intensity Research Articles

Synthesis of Structure-Adjustable R-Au/Pt-CdS Nanohybrids with Strong Plasmon Coupling and Improved Photothermal Conversion Performance.

Noble metal nanomaterials with a localized surface plasmon resonance effect exhibit outstanding advantages in areas such as photothermal therapy and photocatalysis. As a unique plasmonic metal nanostructure, gold nanobipyramids have been attracting much interest due to their strong specific local electric field intensity, large optical cross sections, and high refractive index sensitivity. In this study, we propose a novel three-component hetero-nanostructure composed of rough gold nanobipyramids (R-Au NBPs), Pt, and CdS. Initially, purified gold nanobipyramids are regrown to form R-Au NBPs that have a certain degree of roughness. These R-Au NBP substrates with a rough surface provide more hotspots and strengthen the intensity of localized electric fields. Subsequently, Pt and CdS nanoparticles are selectively deposited onto the surface of R-Au NBPs. Pt nanoparticles can provide more active sites. Each component of this hetero-nanostructure directly contacts others, creating multiple electron transfer channels. This novel design allows for tunable localized plasmon resonance wavelengths ranging from the visible to near-infrared regions. These factors contribute to the final superior photothermal conversion performance of the R-Au/Pt-CdS nanohybrids. Under the irradiation of near-infrared light (1064 nm), the photothermal conversion efficiency of R-Au/Pt-CdS reached 38.88%, which is 4.49, 1.5, and 1.22 times higher than that of Au NBPs, R-Au NBPs, and R-Au NBPs/Pt, respectively.

Waveguide–Cavity Coupling System Based on Topological Edge States and Corner States in Kagome Photonic Crystals

AbstractIn recent years, the topological edge states (TESs) and topological corner states (TCSs) based on high‐order topological photonic insulators have been researched and applied in various fields. Among them, the combination of topological photonics and waveguide–cavity coupling system has attracted much attention of researchers. In this paper, TESs and TCSs based on Kagome lattice photonic crystals (PCs) with rectangular dielectric columns are obtained. In addition, a topological waveguide–cavity coupling system is proposed, realizing the energy coupling between the TES waveguide and the TCS cavity. To further improve the performance of the system, a sandwich‐like waveguide and an extended waveguide are used to replace the original TES waveguide. Interestingly, the proposed extended waveguide–cavity coupling system cannot only achieve the excitation of two TCSs at different frequencies, but also has stronger electric field intensity, narrower resonance bandwidth, and higher quality factor than the other structures. This work provides a new path to design high‐performance micro‐nanointegrated optical devices such as filters, lasers, and resonators.

Compared discharge characteristics and film modifications of atmospheric pressure plasma jets with two different electrode geometries

Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compared the discharge characteristics and the film modifications of atmospheric pressure plasma jets with needle-ring electrode (NRE) and double-ring electrode (DRE). The results show that jet with NRE has stronger electric field intensity and higher discharge power, making it present more reactive oxygen particles and higher electron temperature, but its discharge stability is insufficient. In contrast, the jet with DRE has uniform electric field distribution of lower field intensity, which allows it to maintain stable discharge over a wide range of applied voltages. Besides, the modification results show that the treatment efficiency of PET film by NRE is higher than that by DRE. These results provide a suitable atmospheric pressure plasma jets device selection scheme for polymer film processing process.

Investigation on nano-absorbing precursors in the picosecond regime via the comparative study of HfO2/SiO2 and Ta2O5/SiO2 high-reflectivity coating damage

Laser-induced damage to the final reflective and diffractive optics limits the total output energy of petawatt laser systems with pulse durations ranging from a few hundred femtoseconds (fs) up to a few tens of picoseconds (ps). In this study, the laser damage to HfO2/SiO2 and Ta2O5/SiO2 multilayer dielectric high-reflectivity (HR) coatings induced by a 1053 nm laser with a pulse width of 8.6 ps was studied to investigate the nano-absorbing precursors in ps regimes. The HfO2/SiO2 HR coating exhibited stronger laser resistance than the Ta2O5/SiO2 HR coating. Flat-bottom pits, pinpoints, and funnel pits were the three typical damage morphologies for the experimental HR coatings. The damage to the HfO2/SiO2 HR coating was primarily dominated by flat-bottom pits, whereas dense pinpoints were the most significant damage for the Ta2O5/SiO2 HR coating. The nano-absorbing precursors introduced by the ion-assisted deposition process were proved to be the damage precursors that trigger pinpoints under a strong electric field intensity (EFI). The nano-absorbing precursors located in the second EFI peak of the SiO2 top layer induced the funnel pits. The funnel pits were expected to be the previous stage of the flat-bottom pits. After they grew along the upward-sloping crack and separated from the interface, the flat-bottom pits were formed. In addition, poor-binding interfaces promoted the formation of flat-bottom pits.

Rational Distributed Bragg Reflector Design for Improving Performance of Flip-Chip Micro-LEDs

The distributed Bragg reflector (DBR) has been widely used in flip-chip micro light-emitting diodes (micro-LEDs) because of its high reflectivity. However, the conventional double-stack DBR has a strong angular dependence and a narrow reflective bandwidth. Here, we propose a wide reflected angle Ti3O5/SiO2 DBR (WRA-DBR) for AlGaInP-based red and GaN-based green/blue flip-chip micro-LEDs (RGB flip-chip micro-LEDs) to overcome the drawbacks of the double-stack DBR. The WRA-DBR consisting of six sub-DBRs has high reflectivity within the visible light wavelength region at an incident angle of light ranging from 0° to 60°. Furthermore, the influence of the WRA-DBR and double-stack DBR on performances of RGB flip-chip micro-LEDs is numerically investigated based on the finite-difference time-domain method. Owing to higher reflectivity and less angular dependence of the WRA-DBR, the RGB flip-chip micro-LEDs with the WRA-DBR have a stronger electric field intensity in the top side in comparison with RGB flip-chip micro-LEDs with the double-stack DBR, which indicates that more photons can be extracted from micro-LEDs with the WRA-DBR.

A new approach based on the augmented particle sink effect to remove indoor airborne particulate matter: Experimental study

Traditional indoor air cleaning technologies are mostly equipped with fans and auxiliary components in addition to the core purification unit, and consequently use more energy in the building environment. To energy-efficiently improve indoor air quality, this paper presents a new approach to remove indoor airborne particulate matter. The approach couples the negative pressure effect over the point sink zone by considering the electrohydrodynamic flow generated in a high-voltage gas discharge process to augment the particle sink effect. This facilitates indoor airborne particulate matter to be collected and removed more quickly. We evaluated the influencing factors on the particulate matter removal proportion by laboratory scale experiments: the applied voltage, interelectrode distance, and porosity and shape of the collecting electrode, and compared the particulate matter control performance and energy efficiency of this approach with those of the existing studies. Results showed that the 30 %–40 % porosity of the collecting electrode and stronger electric field intensity had a clearer removal proportion of particulate matter. Moreover, the energy efficiency for 1–2.5 μm particulate matter of this approach (12.7 (m3/h)/W) was 2.3–7.9 times higher than that of the commercially available conventional air cleaners (1.6–5.6 (m3/h)/W). Compared to conventional particle sink purification technique, this approach could save at least 50 % of the sink running time to achieve a better particulate matter removal effect, and shorten approximately 50 % of the 1–2.5 μm particulate matter reverse mass transfer time. This study provides an important reference basis for improving indoor air quality and the creation of a more sustainable society.

Linear and nonlinear optical properties in quantum wells

In this paper, the linear and nonlinear optical properties, especially the optical rectification (OR), the second-harmonic generation (SHG) susceptibility, the third-harmonic generation (THG) susceptibility, the optical absorption coefficients (OACs), and the refractive index changes (RICs) of GaAs-AlGaAs semi-parabolic well (SPW) are studied in detail utilizing the compact density matrix approach and iterative procedure. The states of electron in the SPW with electric field are obtained utilizing the techniques of the displacement harmonic-oscillator and the envelope wave-function. Our results reveal that the confinement frequency, the electric field, the relaxation time, and the incident field strength have considerable influences on the optical properties of the SPW. If it is desired to obtain the OR, SHG, THG, OAC, and RIC with large values, then a relatively weaker incident field strength and confinement frequency, as well as a relatively stronger electric field intensity, should be chosen. If the optical strength is relatively large, then the effect of the nonlinear (third-order) term is important and cannot be neglected when investigating the non-linear optical properties in the SPW. The semiparabolic well is a promising candidate for these properties.

Thermo-optically tunable slot waveguide-based dual mode-splitting resonators with enhanced sharp lineshapes.

Slot waveguide plays an essential role in achieving high-performance on-chip photonic sensors and nonlinear devices. Ideally, slot waveguide features a large evanescent field ratio and strong electric field intensity in the slot, leading to a high waveguide sensitivity. Unfortunately, the microring resonator (MRR) based on the slot waveguide suffers the less steep spectral slope due to the low quality factor induced by the huge optical propagation loss of the slot waveguide. In this work, a novel dual mode-splitting resonator based on the slot waveguide is proposed and demonstrated to steepen the slope of lineshapes. The device is implemented by two racetrack resonators based on a slot waveguide and a feedback waveguide to introduce coherent optical mode interference, which could induce mode-splitting resonance (MR) with sharp asymmetry line shape and large extinction ratio (ER). The proposed device is fabricated by the standard complementary metal-oxide-semiconductor (CMOS) technologies on silicon-on-insulator (SOI) platform, and the characterization results show dual MRs with an ER of 45.0 dB and a slope rate (SR) of 58.3 dB/nm, exhibiting a much steeper lineshape than that of the conventional MRR with slot waveguide. And the resonance can be tuned efficiently by applying various voltages of the TiN microheater. Investigations in dual MRs devices promote many potential applications in the field of optical switching, optical modulating, and on-chip optical sensing.

Universal water disinfection by piezoelectret aluminium oxide-based electroporation and generation of reactive oxygen species

Diverse water microbes in water sources pose serious challenges to conventional disinfection techniques, leading to high oxidant and energy cost and large formation of disinfection by-products. Herein, a piezoelectret aluminium oxide (PEAO) was engineered for water disinfection. The piezo-catalytic disinfection system with ultrasonication induced strong electric field intensity of 8.1 × 107 V/m on PEAO surface, resulting in microbial cell membrane in-situ electroporation followed by penetration of generated reactive oxygen species (ROS, hydroxyl radical, singlet oxygen and hydrogen peroxide). The proposed piezo-catalytic disinfection strategy exhibited universal water disinfection performances among different microbes, ~1000-fold more efficient than an equivalent amount of preformed hydrogen peroxide, thus significantly improved the oxidant utilization and disinfection efficiency and potentially decreasing the formation of disinfection by-products. This work clearly demonstrates the application and mechanism of in-situ versatile water disinfection process via piezo-catalytic of PEAO and further applications in other water treatment fields are expected.

Comparison of surface plasmon polariton characteristics of Ag- and Au-based InGaN/GaN nanocolumn plasmonic crystals

We characterized surface plasmon polariton (SPP) coupling in InGaN/GaN nanocolumn (NC) arrays with Ag- and Au-based plasmonic crystals (PlCs). In both the Ag- and Au-based NC-PlCs, the standing wave SPPs enhanced the light emission from the InGaN/GaN NC arrays. The finite-difference time-domain calculations reproduced the general tendency of the experimental results for the photoluminescence enhancement ratio and SPP resonant wavelength. For the Ag-based NC-PlCs, a stronger electric field intensity was obtained, and the SPP resonance could be controlled over a wide range of wavelengths. Therefore, significant emission enhancement in the visible light region can be realized for the Ag-based NC-PlCs.

Label-Free Near-Infrared Plasmonic Sensing Technique for DNA Detection at Ultralow Concentrations.

Biomolecular detection at a low concentration is usually the most important criterion for biological measurement and early stage disease diagnosis. In this paper, a highly sensitive nanoplasmonic biosensing approach is demonstrated by achieving near‐infrared plasmonic excitation on a continuous gold‐coated nanotriangular array. Near‐infrared incident light at a small incident angle excites surface plasmon resonance with much higher spectral sensitivity compared with traditional configuration, due to its greater interactive volume and the stronger electric field intensity. By introducing sharp nanotriangular metallic tips, intense localization of plasmonic near‐fields is realized to enhance the molecular perception ability on sensing surface. This approach with an enhanced sensitivity (42103.8 nm per RIU) and a high figure of merit (367.812) achieves a direct assay of ssDNA at nanomolar level, which is a further step in label‐free ultrasensitive sensing technique. Considerable improvement is recorded in the detection limit of ssDNA as 1.2 × 10−18 m based on the coupling effect between nanotriangles and gold nanoparticles. This work combines high bulk‐ and surface‐sensitivities, providing a simple way toward label‐free ultralow‐concentration biomolecular detection.

Effect of dielectrophoresis on the coalescence of binary droplets under a non-uniform electric field

Electric field assisted coalescence has been widely applied to separate water from water/oil (W/O) emulsions in the petroleum industry because of its high efficiency and large throughput. Under a non-uniform electric field, the coalescence results from the combination of the dieilectrophoresis force and dipole–dipole attraction. In previous works, the non-uniform electric field was thought to be advantageous because the dielectrophoresis force pulls droplets to a certain place. However, it was shown in this work that different types of dielectrophoresis have different effects on coalescence. Positive dielectrophoresis had adverse effects on causing binary droplets to separate. However, negative dielectrophoresis had an advantageous effect. For positive dielectrophoresis, there is a critical distance of coalescence. The results showed that the critical distance decreases with an increase of the electric field intensity and continuous phase viscosity and also decreases with an increase of the diameter of the droplet in the lower position. Thus, a stronger electric field intensity and lower viscosity might be a disadvantage if the electric field is non-uniform. These conclusions are important supplements for the mechanism of non-uniform electric field assisted coalescence, which has significant guidance for the design of an electrocoalescer.

Design of the 3.0∼5.0 μm Band Wire-Grid Polarizer with Dielectric MgF2 and Metal Al Layers

Low refractive index magnesium fluoride (MgF2) dielectric layers with anti-reflection function were inserted between metal Al gratings and Al2O3 substrates in the form of continuous thin film and grating to construct type-I and type-II sub-wavelength wire-grid polarizers, respectively. The two types of wire-grid polarizers (type-1 and type-11) were designed to operate in the wavelength range of 3.0 similar to 5.0 Am. The structures of type-1 and type-II polarizers were optimized in terms of the substrate material, refractive index and thickness of dielectric layer using the finite-difference time-domain method. The results show that surface plasmon modes at the interface between Al gratings and Al2O3 substrate are weakened owing to the introduction of MgF2 dielectric layer, and a cavity mode in Al grating grooves begins to play a major role. In addition, equivalent refractive index of MgF2 dielectric grating is lower and MgF2 dielectric film is larger than the refractive index of ideal anti-reflection layer. Thus, MgF 2 dielectric grating has better antireflection function and higher transmittance towards the transverse magnetic polarization light. The distribution of electric field intensity indicates the existence of a cavity mode and stronger electric field intensity in the metal grating grooves of type-II. Higher TM transmittance and extinction ratio are achieved for type-11, which are obtained to be 99% and 30 dB at the wavelength of 4.0 mu m, respectively.

Controlling successive ionic layer absorption and reaction cycles to optimize silver nanoparticle-induced localized surface plasmon resonance effects on the paper strip

This study investigates why a silver nanoparticle (SNP)-induced surface-enhanced Raman scattering (SERS) paper chip fabricated at low successive ionic layer absorption and reaction (SILAR) cycles leads to a high SERS enhancement factor (7×108) with an inferior nanostructure and without generating a hot spot effect. The multi-layered structure of SNPs on cellulose fibers, verified by magnified scanning electron microscopy (SEM) and analyzed by a computational simulation method, was hypothesized as the reason. The pattern of simulated local electric field distribution with respect to the number of SILAR cycles showed good agreement with the experimental Raman intensity, regardless of the wavelength of the excitation laser sources. The simulated enhancement factor at the 785-nm excitation laser source (2.8×109) was 2.5 times greater than the experimental enhancement factor (1.1×109). A 532-nm excitation laser source exhibited the highest maximum local electric field intensity (1.9×1011), particularly at the interparticle gap called a hot spot. The short wavelength led to a strong electric field intensity caused by strong electromagnetic coupling arising from the SNP-induced local surface plasmon resonance (LSPR) effects through high excitation energy. These findings suggest that our paper-based SILAR-fabricated SNP-induced LSPR model is valid for understanding SNP-induced LSPR effects.

Resonant Broadband Field Enhancement in Cylindrical Plasmonic Structure Surrounded by Perovskite Environment

We demonstrate the optical response of metal nanoparticles and their interaction with organic-inorganic perovskite (methyl ammonia lead halide (CH3NH3PbI3)) environment using discrete dipole approximation (DDA) simulation technique. Important optical properties like absorption, scattering, and electric field calculations for metal nanoparticle using different geometry have been analyzed. The metal nanoparticles embedded in the perovskite media strongly support surface plasmon resonances (SPRs). The plasmonic interaction of metal nanoparticles with perovskite matrix is a strong function of MNP’s shape, size, and surrounding environment that can manipulate the optical properties considerably. The cylindrical shape of MNPs embedded in perovskite environment supports the SPR which is highly tunable to subwavelength range of 400–800 nm. Wide range of particle sizes has been selected for Ag, Au, and Al spherical and cylindrical nanostructures surrounded by perovskite matrix for simulation. The chosen hybrid material and anisotropy of structure together make a complex function for resonance shape and width. Among all MNPs, 70-nm spherical silver nanoparticle (NP) and cylindrical Ag NP having diameter of 50 nm and length of 70 nm (aspect ratio 1.4) generate strong electric field intensity that facilitates increased photon absorption. The plasmonic perovskite interaction plays an important role to improve the absorption of photon inside the thin film perovskite environment that may be applicable to photovoltaics and photonics.

Analysis of high power microwave induced degradation and damage effects in AlGaAs/InGaAs pHEMTs

The high power microwave (HPM) induced effects in AlGaAs/InGaAs pseudomorphic high electron mobility transistors (pHEMTs) are investigated by simulation and experiments. Simulated results suggest that the HPM damage mechanism is device burnout, which is caused by emerging current path and strong electric field intensity beneath the gate metal. Besides, analysis points out that the gate metal diffusion may be thermally activated, resulting in DC and RF performance degradation. Specifically, a positive shift will occur to the pinch-off voltage while accordingly the small-signal gain will decrease. The HPM injection experiments on the dual-stage pHEMT low noise amplifiers (LNAs) are carried out. Experimental results substantiate that deterioration happens both in the noise figure and in the small-signal gain, which is in agreement with the simulated results. Failure analysis indicates that the HPM induced failure of LNA is attributed to the failure of the first stage pHEMT. Finally, samples dissection analysis using the scanning electron microscopy (SEM) verifies the simulation analysis of the damage mechanism and the location susceptible to burnout. Meanwhile, the assumption of gate metal diffusion is validated by the observation of pits after removing the gate metal. The performance parameters deterioration can be utilized as the degradation (or damage) criteria, and the mechanisms analysis facilitates making reinforcing design.

Electrodeposition of Au/Ag bimetallic dendrites assisted by Faradaic AC-electroosmosis flow

Au/Ag bimetallic dendrites were synthesized successfully from the corresponding aqueous solution via the AC electrodeposition method. Both of the morphologies and compositions could be tuned by the electrolyte concentration and AC frequency. The prepared bimetallic dendrites were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and UV–vis spectroscopy. The underlying dendrite growth mechanism was then proposed in the context of the Directed Electrochemical Nanowires Assembly (DENA) models. Owing to the unscreened voltage dropping in the electrolyte bulk, electromigration dominates the species flux process, and cations tend to accumulate in areas with strong electric field intensity, such as electrode edges. Moreover, Faradaic AC-electro-osmosis (ACEO) flow could increase the effective diffusion layer thickness in these areas during the electrochemical reaction, and leads to dendrite growth. Further Micro-Raman observations illustrated that the Au/Ag bimetallic dendrites exhibited pronounced surface-enhanced Raman scattering (SERS) activity, using 4-mercaptopyridine (4-MP) as model molecules.

Raman mapping probing of tip-induced anomalous polarization behavior in V2O5 waveguiding nanoribbons

Spatially resolved and polarized micro-Raman spectroscopy has been performed on individual V2O5 waveguiding nanoribbons. The experimental results establish that the Raman-antenna patterns are strongly correlated with the local positions of the sample, which gives rise to a pronounced intensity contrast in the polarized mapping for certain phonon modes. The suppressed phonon signals at the body of a ribbon can be enhanced at the end facets, resulting from the effective waveguiding propagation along the nanoribbon and strong local electric field intensity at the ends. The phenomena reported here, in addition to providing insight into the tip effects on optoelectronic nanodevices, will facilitate the rational design of Raman detection in nanostructures.

Possible electromagnetic interference with electronic medical equipment by radio waves coming from outside the hospital.

Electromagnetic interference (EMI) with electronic medical equipment by radio waves from mobile telephone handsets has been reported and is currently receiving wide attention. The possibility of EMI with electronic medical equipment by radio waves coming into the hospital has also been pointed out. But so far, there are no reports measuring the frequency distribution of electric field intensity induced by incoming radio waves. Therefore, we measured electric field intensity induced by radio waves coming into our 11-floor hospital, which was under construction. The maximum intensity observed was about 200 V/m at 2.79 GHz, from airport surveillance radar waves. The maximum intensity induced by radio waves from cellular phone base stations was 1.78 V/m. These data show that various frequencies of radio waves are common in this urban area, and that they induce strong electricfield intensity. This strong electric field intensity might cause EMI with electronic medical equipment. Measurement of the electromagnetic environment should be done by each hospital in urban areas to prevent EMI with electronic medical equipment.

A novel technique of electrical strengthening of soft sensitive clays by dielectrophoresis

A novel technique of electrical strengthening of soil by dielectrophoresis was developed. The process employs an alternating current at high voltage, generating a converging electric field towards the electrode by which a net resultant movement of water in the clay mass is produced towards the direction of stronger electric field intensity. Laboratory tests were developed to investigate the mechanism of this process and to explore the possibility of its application in electrical strengthening of soft sensitive clays. The preliminary results of this study showed that the process is effective, and the shear strength of the treated clay (Wallaceburg clay) increased drastically by several times with a reduction of moisture content of approximately 25% at an applied electric potential of 20 kV for 28 days. When compared with electro-osmosis, similar results are obtained in dielectrophoresis, such as the increase in preconsolidation pressure, decrease in sensitivity, and improvement of stress–strain behaviour. It is also shown that the improvement of soil properties can be greatly enhanced by increasing the applied voltage and electrode depth. Key words : dielectrophoresis, alternating current, converging electric field, high-voltage electrode, dielectric constant, electro-osmosis, soft sensitive clay, shear strength, consolidation.