Electromagnetic Field Intensity Distribution Research Articles

Design and Numerical Analysis of Ultra-Broadband Absorber with Chimney Type Structure

In this study, a novel ultra-broadband absorber is suggested and numerically analyzed to demonstrate that the suggested absorber can achieve an average absorbance of 98.6% in the visible to near-infrared wavelength range (496–2100 nm). The structure of the proposed new ultra-wideband absorber consists of four thin films of silicon dioxide (SiO2), iron (Fe), magnesium fluoride (MgF2), and chromium (Cr). We have examined the structure’s electromagnetic field intensity distribution at numerous selected optical wavelengths and the influence of various structural parameters on the absorption performance of the absorber to offer a physical mechanism underlying the ultra-broadband absorption effect. Furthermore, in the presence of high-performance absorption, the structure has the effect of stabilizing absorption at large angles of incidence and is polarization-independent at vertical angles of incidence. The study also assesses the solar absorption capability of this structure, indicating that the structure has potential applications in solar absorption, such as solar energy collection and conversion, solar power generation, and thermal emitters.

Eelectromagnetic field distribution of whispering gallery mode in a sapphire resonator

When the electromagnetic field in the sapphire resonator corresponds to the whispering gallery mode, it exhibits an extremely low dielectric loss. As result, sapphire oscillator has the characteristics of ultra-low phase noise and high short-term frequency stability. The distribution of electromagnetic field in the sapphire resonator is very important for realizing high-level oscillator. In this work, the radial-axial mode matching method is used to theoretically analyze the distribution of the field mode in the sapphire resonator, and the resonant frequency of the WGH<sub><i>m</i>,0,0</sub> mode is calculated. The field distribution of the sapphire resonator is simulated by the finite element analysis method. The gallery mode number of the sapphire resonator is studied and the electromagnetic field intensity distribution of the WGH<sub>15,0,0</sub> mode in the azimuthal, axial and radial direction are obtained. Finally, a home-made gallery mode analyzer is used to measure the microwave field on the surface of sapphire resonator, which is composed of a three-dimensional rotating stage , the magnetic ring/probe coupling and a vector network analyzer. With the above theoretical analysis, the finite element analysis method and the experimental measurement, the working mode of the sapphire resonator and the resonant frequency of the WGH<sub><i>m</i>,0,0</sub> mode are determined. When the sapphire resonator works in WGH<sub>15,0,0</sub> mode, the resonant frequency is 9.891 GHz, and the parameters of the whispering gallery mode in the resonator are obtained, and the unloaded <i>Q</i> value of the resonator is 94000. When the temperature is 292 K, the frequency-temperature sensitivity of the sapphire resonator working in the WGH<sub><i>m</i>,0,0</sub> whispering gallery mode is about <inline-formula><tex-math id="Z-20221128040038-1">\begin{document}$71.64 \times 10^{-6}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20221156_Z-20221128040038-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20221156_Z-20221128040038-1.png"/></alternatives></inline-formula>. The microwave oscillator consisting of the high <i>Q</i> sapphire resonator can be used to make an oscillator with ultra-low phase noise and high frequency stability.

Perfect Optical Absorbers by All-Dielectric Photonic Crystal/Metal Heterostructures Due to Optical Tamm State.

In this study, we theoretically and experimentally investigated the perfect optical absorptance of a photonic heterostructure composed of a truncated all-dielectric photonic crystal (PC) and a thick metal film in the visible regions. The three simulated structures could achieve narrow-band perfect optical absorption at wavelengths of 500 nm, 600 nm, and 700 nm, respectively. Based on the measured experimental results, the three experimental structures achieved over 90% absorption at wavelengths of 489 nm, 604 nm, and 675 nm, respectively. The experimental results agreed well with the theoretical values. According to electromagnetic field intensity distributions at the absorption wavelengths, the physical mechanism of perfect absorption was derived from the optical Tamm state (OTS). The structure was simple, and the absorption characteristics were not significantly affected by the thickness of the thick metal layer, which creates convenience in the preparation of the structure. In general, the proposed perfect absorbers have exciting prospects in solar energy, optical sensor technology, and other related fields.

Arrangement of Micro Dielectric Particles With Vector Vortex Beam Generated by Dual-Helical Dielectric Cone

Optical vortex is of great value in optical trapping, manipulating, and arranging. Here, we propose a dual-helical dielectric cone to generate a dual-vortex beam which can be used to manipulate and arrange dielectric microparticles in three-dimensional space. With the finite-difference time-domain simulation, we calculate the electromagnetic field intensity distribution, phase, and Poynting vector during the propagation of the dual-vortex beam, the optical force and optical torque on the microparticles in the range of dual-vortex beam is also considered. In the experiment, we use the phase mask projected on spatial light modulator to generate a dual-vortex beam, which can trap, manipulate, and arrange the fluorescent microparticles to a specific and stable shape, which is consistent with the results of our simulation calculations. The dual-vortex beam generated by the dual-helical dielectric cone provides a feasible method three-dimensional optical manipulation, which is significant in biophotonical researches.

Fabrication of a Plasmonic Nanoantenna Array Using Metal Deposition on Polymer Nanoimprinted Nanodots for an Enhanced Fluorescence Substrate.

A simple and cost-effective method is proposed herein for a plasmonic nanoantenna array (PNAA) for the fabrication of metal-enhanced fluorescence (MEF) substrates in which fluorophores interact with the enhanced electromagnetic field generated by a localized surface plasmon to provide a higher fluorescence signal. The PNAA is fabricated by the deposition of a silver (Ag) layer on an ultraviolet (UV) nanoimprinted nanodot array with a pitch of 400 nm, diameter of 200 nm, and height of 100 nm. During deposition, raised Ag nanodisks and a lower Ag layer are, respectively, formed on the top and bottom of the imprinted nanodot array, and the gap between these Ag layers acts as a plasmonic nanoantenna. Since the thickness of the gap within the PNAA is influenced by the thickness of Ag deposition, the effects of the latter upon the geometrical properties of the fabricated PNAA are examined, and the electromagnetic field intensity distributions of PNAAs with various Ag thicknesses are simulated. Finally, the fluorescence enhancement factor (FEF) of the fabricated PNAA MEF substrate is measured using spotted Cy5-conjugated streptavidin to indicate a maximum enhancement factor of ~22× for the PNAA with an Ag layer thickness of 75 nm. The experimental results are shown to match the simulated results.

Enhancement of THz absorption in monolayer graphene for light at Brewster angle incidence

• A tunable THz graphene absorber is proposed and investigated. • Above 50% resonant absorption is achieved for light at Brewster angle incidence. • The absorption performance can be tuned and extended to multichannel. The enhancement of absorption in graphene for light at Brewster angle incidence is investigated. It is achieved by placing a graphene on a resonant Brewster filter that incorporating a spacer layer. The absorber presents above 50% absorption at resonance, which is attributed to the excitation of guided mode resonances. The electromagnetic field intensity distributions are illustrated to intuitively confirm the physical mechanism of such phenomenon. Moreover, the influence of geometric parameters on absorption is investigated to provide a useful guidance for practical fabrication. Besides, it is found that the absorption properties not only can be controlled by adjusting the incident angle but also can be dynamically tuned by changing the Fermi level. Last, the graphene absorption can be easily extended to multichannel by only an increase in the thickness of spacer. The results open new avenues for combining graphene with general guided mode resonance structure to enable novel optoelectronics device applications.

USE OF COMPLEX OF ELECTROMAGNETIC ANALYSIS OF PACKAGED PRODUCTS FOR ASSESSING ELECTROMAGNETIC COMPATIBILITY OF ELECTRONIC DEVICES

The article describes the experience of using a complex electromagnetic analysis of cased products based on the near-field electromagnetic radiation scanner to assess the electromagnetic compatibility of electronic devices. The structural scheme of the complex and its main characteristics are presented, which consist of the characteristics of the scanner itself and the characteristics of the connected spectrum analyzer. Descriptions of preparations for the re-installation and configuration of application software for managing the scanner. The above formula for calculating the time to scan, the algorithm for the operation of the device, the characteristics of the measuring sensors included in the delivery package and the features of working with the complex. The results of spectral and spatial analysis of electronic devices are shown with a 3D pattern of electromagnetic field intensity distribution. Conclusions are drawn based on the analysis of construction of operational experience.

Ultra-narrow perfect graphene absorber based on critical coupling

Abstract A polarization-independent perfect graphene absorber is numerically demonstrated. The novel absorber is composed of an array of dielectric square resonators and a graphene monolayer on a Bragg reflector. An absorption peak at a wavelength of 1550 nm with an absorbance of up to ∼ 99 % is achieved, owing to the critical coupling effect. Moreover, the designed graphene absorber exhibits an ultra-narrow spectrum bandwidth with an ultra-high quality factor, owing to the combined effects of the guided mode resonance achieved with the dielectric square resonators and photonic band gap with the Bragg reflector. In addition to the numerical results, an analysis model based on the coupled-mode theory is presented. Moreover, the electromagnetic field intensity distributions are plotted to provide a physical interpretation of the complete absorption. This study paves the way for the development of a perfect ultra-narrow spectrum-selective graphene absorber.

Packaged Droplet Microresonator for Thermal Sensing with High Sensitivity.

Liquid droplet and quasi-droplet whispering gallery mode (WGM) microcavities have been widely studied recently for the enhanced spatial overlap between the liquid and WGM field, especially in sensing applications. However, the fragile cavity structure and the evaporation of liquid limit its practical applications. Here, stable, packaged, quasi-droplet and droplet microcavities are proposed and fabricated for thermal sensing with high sensitivity. The sensitivity and electromagnetic field intensity distribution are analyzed by Mie theory, and a quantified definition of the quasi-droplet is presented for the first time to the best of our knowledge. By doping dye material directly into the liquid, lasing packaged droplet and quasi-droplet microcavity sensors with a high thermal sensitivity of up to 205.3 pm/°C are experimentally demonstrated. The high sensitivity, facile fabrication, and mechanically robust properties of the optofluidic, packaged droplet microresonator make it a promising candidate for future integrated photonic devices.

Multichannel unidirectional perfect absorbers on sandwich structures with truncated symmetric photonic crystals

We experimentally studied unidirectional perfect absorbers with asymmetric sandwich structures composed of two thick metallic films with different thicknesses and a truncated symmetric photonic crystal (PC). Single-channel and multichannel near-perfect absorbers were obtained by adjusting period number of the PC. According to electromagnetic field intensity distributions at absorption wavelengths, the physical mechanism of near-perfect absorption derived from the coupling effect between optical Tamm state and Fabry-Pérot resonance. The unidirectional absorption phenomena were attributed to weak electric field distributions at absorption wavelengths for opposing directions of light incidence. The experimental values showed good agreement with theoretical results.

Experimental investigation of multiple near-perfect absorptions in sandwich structures containing thin metallic films.

We experimentally investigated near-perfect optical absorption in sandwich structures comprising a thin metallic film whose thickness is larger than the skin depth, a top dielectric layer and a truncated photonic crystal. Single and multiple near-perfect absorptions were realized by tuning the thickness of the top layer. Based on the electromagnetic field intensity distributions at the absorption wavelengths, single near-perfect absorption originated from the tunneling effect of the optical Tamm state, while multiple near-complete absorptions mainly originated from Fabry-Perot resonances. Additionally, the structures showed good one-way absorption properties. The experimental results agreed well with theoretical values. These structures may be important for the fabrication of single or multichannel perfect absorbers.

Thin cylindrical slot in an optical microdisk cavity for sensing biomaterials

In this paper, we propose and investigate a thin cylindrical slot etched into a disk shape optical microcavity (MC) aiming for sensing biomaterials in a label-free style. Supporting whispering gallery modes (WGMs), with remarkably large quality factor to modal volume ratio (Q/Vm) of the optical MC structures that penetrate in the slot region, enables us to perform sensing. Three different geometries for the side walls of host microdisk cavities, including vertical, 60° wedged, and half-circular cross section, are selected for investigations. In each individual case, the radial position, width, and height of the thin cylindrical slot are varied. The electromagnetic (EM) field intensity distributions (mode mapping profiles) of the WGMs show funneling of the intensified fields into the slot area that possessing nearly the same high Q values. Tuning the slot position, width, and depth for a suitably chosen WGM, sensing could be optimized for different biomaterials. Sensitivity value as high as 75 nm/RIU is calculated for the half-circular side wall microdisk. The proposed WGM-based slotted microdisk, as a state-of-the-art device which can operate, such as lab-on-chip structure, would function as a sensitive biosensor, even down to the single biomolecule levels.

Plasmonic Spectroscopy: The Electromagnetic Field Strength and its Distribution Determine the Sensitivity Factor of Face-to-Face Ag Nanocube Dimers in Solution and on a Substrate

Using the DDA method, the spectral sensitivity of a 42 nm Ag nanocube dimer oriented face-to-face in solution and placed on a substrate was investigated. The sensitivity factor was calculated as a function of both the plasmonic band that was analyzed and the refractive index of the substrate. We found that the maximum value of the electromagnetic field intensity of a given plasmonic band is not directly proportional to its extinction intensity. Also, the sensitivity factor of a plasmonic band does not depend on its extinction intensity, but rather, it is a function of the maximum value of the plasmonic electromagnetic field intensity distribution. The presence of a high refractive index substrate drastically affects the extinction intensity of a given band and selectively enhances specific plasmonic bands on the basis of their electromagnetic field distribution. The distribution of the electromagnetic field intensity on the surface of the Ag nanocube dimer is also affected by the presence of a substrate w...

Enhanced nonlinear optical response from individual silicon nanowires

We report about the experimental observation and characterization of nonlinear optical properties of individual silicon nanowires of different dimensions. Our results show that the nonlinear light has different components, one of them corresponding to the second harmonic generation (SHG). The SHG strongly depends on the polarization of the optical excitation and nanowire diameter, and gives access to the local electromagnetic field intensity distribution. Furthermore, we show that the second harmonic, when observed, is enhanced compared to bulk silicon and is sensitive to optical resonances supported by the nanowires. This offers different perspectives on the definition of silicon-based nonlinear photonic devices.

Electromagnetic field intensity distribution along focal region of a metallic circular reflector covered with a plasma layer

Theoretical analyses has been carried out to study the deviation of the electromagnetic field intensity distribution in the focal region of a long metallic circular reflector that contains a uniform cold collisional plasma layer on its surface. The electromagnetic field intensity expressions along the focal region have been obtained using Maslov’s method. Maslov’s method is systematic procedure, which combines the simplicity of ray optics and the generality of transform methods. The derived analytical field expressions in the focal region have been solved numerically. The reflected and transmitted field intensity distributions from the plasma layer along the focal point were examined. The effects of some physical parameters such as the plasma frequency, the thickness of plasma layer and the effective collision frequency on the transmitted field intensity distribution along the focal region are studied. The results are found to be in a good agreement with results obtained using Kirchhoff’s approximation.

Coupled Photonic Systems Between Core-Shell Nanoparticle and Integrated Microresonator

We have numerically investigated the unique effects of the core-shell nanoparticles on the integrated microdisk resonator. By attaching the core-shell nanoparticle to the disk resonator with gold core and polymer shell, the coupling between the disk resonator and the core-shell nanoparticle results in shift of the resonance wavelength of the disk resonator, depending on the core size/shell thickness of the nanoparticle. An invisibility phenomena found from the coupled core-shell nanoparticle and integrated disk resonator system is emphasized; at certain core size/shell thickness ratio, compared with the original resonance wavelength without core-shell nanoparticle, there is almost no resonance wavelength shift observed. The detailed interaction mechanism between the disk resonator and the nanoparticle is revealed in the electromagnetic field intensity distribution at the resonator resonance wavelength. The dependence of the position and number of core-shell nanoparticles is also discussed. Future studies on this coupled photonic systems will stimulate wide variety of applications.

A Multi-Tag Emulator for the UHF RFID System

Radio-frequency identification technology has been booming over the past few years, and the corresponding product varieties and standards are becoming more and more widely available. It is important to test the products and standards before putting them on the market, but it is inconvenient to simulate the real environment to test the efficiency of a reader, because different tag distributions in varying applications will lead to different electromagnetic field intensity distributions. In this paper, based on the analysis of the responses of multiple tags and quantification of the response times, a multitag emulator is proposed that is capable of emulating the responses of multiple passive ISO/IEC 18000-6C tags. A verification system is set up, and the measurement results show that, based on the pipeline structure at the frequency of 40 MHz, the system can emulate 50 tags with a link data rate of 40 kb/s. This multitag emulator can be applied not only to verify the inventory and anti-collision algorithm but also to debug a reader. Compared to the conventional reading efficiency test method, the proposed method is capable of achieving the same goal and saving time and resources.

FDTD Analysis of Nanoscale Temperature Distribution Induced by Near-Field Photothermal Effect

We have developed a novel nanoscale patterning method of self-assembled monolayer (SAM) using near-field light. This method utilizes the thermal desorption of constituent molecules of a SAM (e.g. the desorption temperature of Octadecanethiol on Au is 130～230 °C) through the irradiation with near-field light, which can make noncontact and noncontaminating patterning of the SAM at nanoscale. In this paper, the near-field photothermal effect is numerically analyzed by the finite difference time domain (FDTD) method, and the electromagnetic field intensity and temperature distributions are estimated. The sample consists of Au thin film as a bonding layer with thiolated molecules of SAM, Ti thin film as an adhesion layer for Au, and SiO2 substrate. In the analysis, the shape of the near-field optical fiber probe and the thickness of the thin film layer are considered. In the case of the thick Au layer with a double-tapered near-field optical fiber probe, the temperature of the fiber-tip becomes higher than that of Au surface. The strong heating of the probe tip causes a fatal damage of the coating metal of the fiber, therefore it is difficult to couple the high intensity laser into the near-field optical fiber probe in order to reach the desorption temperature. On the other hand, the desorption temperature can be achieved with the 10 nm-thick Au thin film. Moreover, in order to gain high optical intensity enhancements, the triple-tapered near-field optical fiber probe is utilized. Our simulations confirm extremely high temperature distribution on the sample surface by using the triple-tapered near-field optical fiber probe with 10 nm-thick Au thin film layer on 50 nm-thick Ti membrane.

Lasing thresholds of helical photonic structures with different positions of a single light-amplifying helix turn

Numerical simulation is used to assess the lasing threshold of helical structures of cholesteric liquid crystals (CLCs) in which only one turn amplifies light. This turn is located either in the centre of symmetric structures of various sizes or in an arbitrary place in asymmetric structures of preset size. In all cases, we find singularities in light amplification by a one-dimensional CLC structure for the most important band-edge modes (m1, m2 and m3) and plot the threshold gain coefficient against the position of the amplifying turn. For the symmetric structures, the lasing threshold of the m1 mode is shown to vary linearly with the inverse of the square of the cavity length. Moreover, modes with a lower density of photonic states (DOS) in the cavity may have a lower lasing threshold. This can be accounted for by the dependence of the density of photonic states on the position of the amplifying turn and, accordingly, by the nonuniform electromagnetic field intensity distribution along the cavity for different modes. In the asymmetric structures, the same field energy distribution is responsible for a correlation between and DOS curves.

赤外線2次元ロックインアンプを用いた回路近傍電磁界強度分布測定法の提案

赤外線2次元ロックインアンプを用いた回路近傍電磁界強度分布測定法の提案