Electromagnetic Field Intensity Research Articles

IMAGING OF MICROWAVE NEAR-FIELD DISTRIBUTION OF GPS PATCH ANTENNA

Microwave near-field distribution of the GPS patch antenna was visualized by a thermo-elastic optical indicator microscopy (TEOIM) technique at $1.575~GHz$. Visualization of the antenna radiation is realized to describe the electromagnetic field intensity and distribution depending on the distance from the antenna surface and optical indicator. Experimental data was compared and confirmed with simulation results, which are in good agreement. Possible applications of the TEOIM system were discussed.

A surface-enhanced Raman scattering aptasensor for Escherichia coli detection based on high-performance 3D substrate and hot spot effect

A surface-enhanced Raman scattering (SERS) aptasensor was established for highly sensitive and selective detection of Escherichia coli (E. coli). Chitosan hydrogel modified with E. coli aptamer (Apt) functionalized silver nanoparticles was constructed as a SERS 3D substrate for specific bacteria enrichment, while the Raman signaling molecule 4-mercaptobenzoic acid and E. coli Apt modified gold nanostars were prepared for the sensitive quantification of E. coli. The aptasensor exhibits intense electromagnetic field enhancement in multiple hot spot regions, including the spikes and the gap between adjacent nanostars and that between gold nanostars and silver nanoparticles. Due to the hot spot effect coupled with the selective recognition ability, a detection limit of 3.46 CFU/mL with a wide dynamic linearized range from 3.2 × 101 to 3.2 × 107 CFU/mL could be achieved without other non-target bacteria interference. Moreover, this SERS aptasensor was applied to detect E. coli in actual samples with a good recovery rate (>90%). Therefore, the developed SERS aptasensor paves a new avenue for the detection in the field of food safety and environmental pollution by replacing the corresponding aptamers.

Self-Assembled Supercrystals Enhance the Photothermal Conversion for Solar Evaporation and Water Purification.

Photothermal materials can convert renewable solar energy into thermal energy and have great potential for solar water evaporation. Copper sulfide (Cu2- x S) is an easily available and inexpensive plasmonic material with a high photothermal conversion efficiency and can be applied to solar evaporation and water purification. Monodispersed Cu7 S4 nanoparticles (NPs) and supercrystalline self-assembled superparticles are obtained via wet chemical synthesis and micelle self-assembly. The photothermal properties of the superstructures are investigated using the finite difference time domain method and laser radiation photothermography. The results show that the electromagnetic field intensity and photothermal efficiency of the self-assembly are significantly higher than those of isolated NPs, which is due to the plasmonic coupling of the NPs. The evaporation efficiency of the superstructure is significantly higher than that of isolated NPs, the metal salt ion and total organic carbon concentrations in the waterbody significantly decrease after evaporation, and the water polluted by high salt and organic dye concentrations is purified. The water quality significantly improves after the lake water from Fuxian Lake in the Yunnan-Guizhou Plateau of China is used for solar evaporation. The color changes from pale yellow to colorless and the ion and total organic carbon contents significantly decrease.

Consideration of Harmonic Distortions in Modeling the Electromagnetic Fields Generated by Power Lines Feeding Railway Traction Substations

In setting up intelligent electric networks, special attention is paid to the operational safety of electric power facilities and reduction of their negative impact on the personnel and environment. Significant electromagnetic field intensity levels can be observed at such objects. To ensure electromagnetic safety under the modern conditions characterized by large-scale introduction of digitalization tools, it is necessary to develop electromagnetic field digital modeling algorithms. Adequate models of the electromagnetic field generated by power transmission lines can be obtained on the basis of methods for determining the electric power system operation modes in phase coordinates. A methodology for analyzing electromagnetic safety has been developed on the basis of such models, which differs from the known approaches in being systematic, versatile, adequate to the external environment, and comprehensive. By using the newly developed methodology, it is possible to determine the intensity of electromagnetic fields generated by multi-wire transmission lines taking into account higher harmonic components of currents and voltages. Under the conditions of digitalizing the electric power industry, the use of the proposed methodology for practical applications will make it possible to analyze the conditions of electromagnetic safety in electric power systems on a scientifically sound basis and develop measures for its further improvment.

Implementation of rapid microwave sintering using a 24GHz gyrotron system.

Rapid microwave sintering of different oxide ceramics with heating rates up to 300 °C/min and zero hold time has been implemented using a 24GHz gyrotron-based system for high-temperature processing of materials. The design of the system, principle of operation, and process control are described. Particular attention is given to the design of thermal insulation assemblies and the implementation of temperature measurement in an environment with intense electromagnetic fields. A description of an optical system for dilatometry and temperature measurement is presented. The interrelation between the automatically regulated output power of the gyrotron and the microwave power absorbed volumetrically in the sample is analyzed on the basis of energy balance considerations. The analysis is illustrated by considering examples of rapid sintering processes with ZnO-based and BaTiO3 ceramic samples making use of direct and susceptor-assisted microwave heating. It is demonstrated that an increase in the volumetrically absorbed power leads to the development of a controlled thermal instability, which results in a lower temperature of the densification onset.

Effects of ELF-EMF Treatment on Depression

Introduction: Depression is an extremely widespread disorder that is also highly impactful on the quality of life and general health of individuals, on a global scale. The aim of this study was a preliminary assessment of a potential non-pharmacological treatment, based on extremely low frequency and intensity electromagnetic fields (ELF-EMF), which could potentially reduce the impact of depression on the lives of sufferers. Materials and methods: A preliminary case-control study based in 2centres was conducted during the second half of 2020. The recruited participants were subject either to ELF-EMF treatment (Group α) or to a placebo treatment (Group β) for a total of 5 sessions. Treatment involved non-focused exposure using a radiant mat associated with focused exposure in the cranial area using the same ELF-EMF parameters. Each individual session lasted 36 min and the same ELF-EMF program was used for all 5 therapeutic sessions. The effects of treatment were evaluated by giving the subjects the following self-administration tests: Zung Self-Rating Depression Scale (SDS), Beck Depression Inventory Scale (BDI), and Short-Form 12 (SF12). The tests were administered before starting the treatment cycle (T0), after the 5 sessions (T1), and at a 2 month follow-up (FU). Results: Statistical significance indicating an improvement in the depressed state perceived by the participants was achieved with both the SDS and the BDI, at T1 (T1: SDSα 37.8, SDSβ 46.6, p = 0.012; BDIα 8.7, BDIβ 20.4, p = 0.004) and persisting at FU (T1: SDSα 39.1, SDSβ 49, p = 0.037; BDIα 10, BDIβ 19.9, p = 0.04). As regards SF12, the mental part of the test (MCS12) exhibited a significant improvement at T1in the treated group compared to the placebo (MCS12α 47.40, MCS12β 40.48, p = 0.048), but this was not confirmed at FU. During the treatment period there were no drop-outs from the 2 groups and no adverse events were reported in the treatment group. Conclusions: Treatment with ELF-EMF demonstrated safety and efficacy for reducing the gravity of perceived depressed state.

Uncommon Electromagnetic Radiations Related to Extra-High Voltage/Ultra-High Voltage Power Projects in China

Based on the high-resolution electromagnetic field intensity observed by the DEMETER satellite, the harmonic electromagnetic radiations in the ionosphere closely above the extra-high voltage and ultra-high voltage power projects in the Chinese power grid have been detected. In the time-frequency spectrograms, these radiations are characterized by parallel spectral lines with spacings of 50, 100, 150, or 600 Hz. The highest frequency can reach approximately 8,850 Hz. The radiations are probably attributed to the nonlinear devices such as converters or geomagnetic disturbance. The harmonic radiations over alternating current-to-direct current (AC-to-DC) substations of power system are generally more diverse and stronger than those over AC-to-AC substations. The measurements on the ground demonstrate that the weak magnetic radiations at several kilohertz with an intensity in the order of nT do exist around substations. A simple physical model is established to understand the characteristics of harmonic radiations propagating from the Earth’s surface to the ionosphere.

Laser-assisted doubly charged Higgs pair production in Higgs triplet model (HTM)

In the framework of Higgs triplet model (HTM), we study the pair production process of doubly charged Higgs bosons via $e^{+}e^{-}$ annihilation in the presence of a laser field with circular polarization . We begin our work by presenting the theoretical calculation of the differential cross section in the centre of mass frame including both $Z$ and $\gamma$ diagrams. Then, from the numerical analysis of the production cross section's dependence on the laser field parameters, we have shown that the laser-assisted total cross section decreases as far as the electromagnetic field intensity enhances or by decreasing its frequency. Finally, we analyze the variation of the total cross section versus the mass of the doubly charged Higgs boson by fixing the laser field parameters and the centre of mass energy, and we have found that the order of magnitude of the cross section decreases as long as $M_{H^{\pm\pm}}$ increases.

Impact of Electromagnetic Field on Bacterial Population and Physicochemical Properties of Cassava Wastewater

The release of industrial wastewaters into the environment is a major source of toxic contaminants causing global health and environmental challenges. This study aimed to investigate the impact of electromagnetic field (EMF) treatment on bacterial population and physicochemical characteristics of cassava wastewater. Cassava wastewater sample was collected from point source of a small-scale cassava industry in Akure, Nigeria. Sample was thereafter treated with EMF of varying intensities (70- 130nT) and bacterial population and physicochemical properties of raw and treated wastewater sample were determined using standard microbiological, physical and chemical analytical techniques. Results revealed a total bacterial count of 1.34 x 105cfu/ ml. Identity of bacterial genera isolated from wastewater were Enterobacter aerogenes, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi (Gram negative) while the Gram positive bacteria were Staphylococcus aureus, Bacillus cereus, Bacillus subtilis and Lactobacillus sp. Results also revealed that treatment of wastewater sample with EMF significantly reduced the bacterial load and physicochemical parameters of the sample and dependent on EMF intensity and duration of exposure. Results revealed a decline in bacterial population from 1.34 x 105- 1.0 x 104 at intensities of 70nT-130nT and exposure time of 0- 144hr with the lowest count obtained at 130nT and the highest at 70nT. This study concludes that the use of Electromagnetic Field holds promise as an effective, non-invasive and eco-friendly strategy to improve the physical, chemical and biological quality of wastewater before discharge into the environment.

Lateral and angular misalignments of coil in wireless power transfer system

Wireless power transfer requires the transmission and reception of energy through coils arranged coaxially and the direction does not change to ensure maximum transmission efficiency and power. However, in actual working environments, coils have lateral and angular misalignments, thereby reducing the transmission performance. In this study, we investigate the transmission efficiency of coils and the mutual inductance of the lateral and angular misalignments theoretically. Coils with lateral and angular misalignments are modeled with the Maxwell simulation software. Finally, a 3D test experimental platform is built. The experimental results show that the use of a magnetic isolation material on the coil can effectively improve the electromagnetic field intensity of the system. The coupling coefficient of the two coils is increased by more than 15%. At a coupling distance of 5 mm, the coupling mechanism with ferrite is approximately 10% more efficient than that without ferrite. Furthermore, it shows that when the misalignment is large, the magnetic isolation material can significantly improve the efficiency of the wireless charging system.

Extremely Low-Frequency Electromagnetic Fields Increase Cytokines in Human Hair Follicles through Wnt/β-Catenin Signaling.

Hair loss is a chronic disorder that affects many people; however, a complete treatment has not yet been developed. Therefore, new therapeutic agents for preventing hair loss must be developed, and electromagnetic field (EMF) therapy has been proven to be a promising medical treatment in various fields, including hair loss treatment. This study evaluated the effect of extremely low-frequency electromagnetic field (ELF-EMF) intensity and exposure time by analyzing the expression of cytokines and anagen-related molecules, which influence hair activation and growth, in hair bulb spheroid (HBS) and hair follicle (HF) organ cultures. ELF-EMFs did not induce toxicity in the HBSs, as verified via the lactate dehydrogenase (LDH) assay. Moreover, an ELF-EMF intensity of 5–20 G promoted the expression of ALP, versican, β-catenin, and several cytokines (VEGF, PDGF, FGF-10, and ET-1) in HBSs. Immunohistochemical staining showed that ELF-EMF at an intensity of 5–20 G upregulated ALP and β-catenin and decreased TUNEL staining in HBS. Moreover, HFs exposed to ELF-EMF for 60 min exhibited an increase in hair length and a 1.5-fold increase in IL-4, ICAM-1, ALP, and versican mRNA expression compared to the control. Immunohistochemical staining indicated that 60 min of ELF-EMF can increase the expression of ALP and β-catenin and decreases TUNEL staining in organ cultures. Collectively, our results demonstrated that ELF-EMF exposure at a 10 G intensity for 60 min promoted hair shaft growth in HFs due to the effect of cytokines and adhesion molecules via the Wnt/β-catenin pathway. Therefore, ELF-EMF is a promising treatment for hair loss.

Exploiting Plasmonic Hot Spots in Au-Based Nanostructures for Sensing and Photocatalysis.

ConspectusLocalized surface plasmon resonance is a unique property appearing in certain metal nanostructures, which can generate hot carriers (electrons and holes) and bring about an intense electromagnetic field localized near the surface of nanostructures. Specific locations, such as the rough surfaces and gaps in nanostructures, where a strong electromagnetic field is formed are referred to as hot spots. Hot-spot-containing plasmonic nanostructures have shown great promise in molecular sensing and plasmon-induced catalytic applications by exploiting the unique optical properties of hot spots. In this Account, we will review our recent developments in the synthesis of Au nanostructures consisting of multiple hot spots and Au-based heteronanostructures combining secondary active metals or semiconductors with Au nanostructures as promising plasmonic platforms for hot-spot-induced sensing and photocatalysis. We first provide a brief introduction to Au nanocrystals and Au nanoparticle assemblies with multiple hot spots. High-index-faceted hexoctahedral Au nanocrystals having multiple high-curvature vertices and edges are beneficial for the generation of an intense and reproducible electromagnetic field, which can enhance the performance of surface-enhanced Raman scattering-based molecular sensing. In addition, the engineering of interparticle gaps in Au nanoparticle assemblies to have a controlled size and a certain number of gaps can lead to the enhancement of plasmonic properties due to the significant amplification of the electromagnetic field at interparticle gaps. We then discuss hot-spot-containing Au-based heteronanostructures prepared by growing secondary components on the aforementioned Au nanostructures. With a combination of merit from strong plasmon energy formed by hot spots and catalytically active secondary materials, Au-based heteronanostructures have emerged as an attractive and versatile catalyst platform for various photocatalytic reactions. Through the control of key factors governing the photocatalysis of Au-based heteronanostructures, such as the coupling manner, shell thickness of secondary materials, and intimacy of contact, the plasmon energy formation of heteronanostructures and its transfer to catalytically active materials can be optimized, leading to the promotion of photocatalysis, such as photocatalytic hydrogen evolution. The rational design of Au nanostructures and Au-based heteronanostructures with multiple hot spots not only could realize enhanced sensing and photocatalysis but also could enable the understanding of the geometry-performance relationship. It is envisioned that the developed strategies can offer new opportunities for the design of various high-efficiency catalytic platforms.

Nanoantenna effect dependent on the center structure of Bull's eye-type plasmonic chip.

A bright spot is observable in the center of Bull's eye plasmonic pattern with a fluorescence microscope due to the plasmonic nanoantenna effect. In this effect, a propagating wave of surface plasmon resonance concentrates in the center. This study focused on the relationship between the center structure of Bull's eye pattern and the nanoantenna effect in four fabricated Bull's eye-type plasmonic chips with centers of different sizes (full- or half-pitch diameter) and shapes (convex or concave). The fluorescence intensity of the fluorescent nanoparticles adsorbed to these plasmonic chips was measured with an upright-inverted microscope to evaluate the plasmonic chip enhancement factor composed of the product of the excitation and emission enhancement and individual factors. When the emission enhancement factor was investigated under nonresonance excitation conditions, by the disappearance of a bright spot, excitation enhancement was found to contribute to the plasmonic nanoantenna effect. The concave Bull's eye structure with a half-pitch diameter demonstrates the highest nanoantenna effect due to the formation of a larger constructive wave in the superposition of the diffraction wave of incident light under resonance conditions. In addition, the electromagnetic field intensity simulated by discrete dipole approximation agrees with the microscopy results. Overall, the results indicate that the plasmonic nanoantenna effect could be controlled depending on the resonance condition and center structure.

Induced Optical Bistability in Small Metal and Metal Coated Particles with Nonlinear Dielectric Functions

The theoretical and numerical study of the enhancement of the amplitude of the incident electromagnetic radiation in small metal ellipsoidal particles and spherical dielectric particles covered by a metal shell with nonlinear dielectric functions is carried out. If the frequency of the external radiation approaches the frequency of surface plasmons of a metal, the local field in the particle considerably increases. At intense incident electromagnetic fields (laser radiation), it is necessary to consider the nonlinear part of the dielectric functions of a metal and a dielectric. This results in the induced optical bistability (IOB) when one value of the amplitude of the incident field initiates three values of the local field in a particle. The domains of IOB are specified in the case where the radiation wavelength is much larger than the typical size of particles. The range of external fields and the IOB frequency are specified. A decrease of the IOB domain and an increase of the critical fields with increase in the damping of plasmon vibrations are discussed. The results of numerical computations for typical small silver particles are presented graphically.

Effect of pulsed electromagnetic field versus pulsed high intensity laser in the treatment of men with osteopenia or osteoporosis: a randomized controlled trial

Background: Osteoporosis has been related to a negative impact on several aspects of patient health, including physical, mental, and emotional well-being. The objective of this study was to examine the effects of pulsed electromagnetic fields (PEMF) and pulsed Nd-YAG laser therapy (HILT) on men with osteopenia or osteoporosis. Methods: Ninety-five men with osteopenia or osteoporosis (mean age, 52 years; mean height, 176 cm; mean weight, 83 kg; mean body-mass index (BMI), 26.86 kg/m2) took part in the study, and they were randomly assigned to one of three groups: Group 1 received PEMF and exercise program (PEMF +EX), Group 2 received HILT and exercise program (HILT+EX), and Group 3 received exercise program only (EX). PEMF was applied three times per week for 12 weeks using a full-body mat, while HILT was applied to the lower back and hip regions with a total dose of energy of 3000 J delivered in two treatment stages. Flexibility, aerobic exercise, strength, weight-bearing, and balance exercises are included in exercise program, which is followed by whole-body vibration training. Bone mineral density (BMD) of the total hip and lumbar spine, bone markers, health-related quality of life (HRQoL), and fall risk are all outcome measures. Results: There were no significant differences in the parameters between the groups at the baseline (P > 0.05). Patients in all groups, however, showed significant improvements in all measured parameters following treatment (P< 0.05), with Group 1 and Group 2 showing much greater improvements than Group 3. Conclusion: After 12-weeks of treatment, PEMF combined with exercise is more effective than HILT combined with exercise or exercise alone in increasing BMD and promoting bone formation, suppressing bone-resorption markers, and improving quality of life and fall risk, with the effects lasting up to six months. This study was registered in the ClinicalTrial.gov PRS (NCT05029440, 26/08/2021).

Two-Dimensional Self-Assembly of Au@Ag Core-Shell Nanocubes with Different Permutations for Ultrasensitive SERS Measurements.

Different self-assembly methods not only directly change the arrangement of noble metal particles on the substrate but also indirectly affect the local electromagnetic field distribution and intensity of the substrate under specific optical excitation conditions, which leads to distinguished different enhancement effects of the structure on molecular Raman signals. In this paper, first, the gold species growth method was used to prepare the silver-coated gold nanocubes (Au@Ag NCs) with regular morphology and uniform size, and then the two-phase and three-phase liquid–liquid self-assembly and evaporation-induced self-assembly methods were used to obtain the substrate structure with different NC arrangement patterns. The optimal arrangement of NCs was found by transverse comparison of Raman signal detection of probe molecules with the same concentration. Subsequently, surface-enhanced Raman scattering (SERS) measurements of Rhodamine (Rh6G) and aspartame (APM) were carried out. Furthermore, the finite element method (FEM) was employed to calculate the local electromagnetic fields of the substrates with different Au@Ag NC arrangements, and the calculated results were in agreement with the experimental results. The experimental results show that the SERS-active substrate was largely associated with the different arrangements of Au@Ag NCs, and the island membrane Au@Ag NCs array substrate obtained by evaporation-induced self-assembly can generate a strong local electromagnetic field due to the edge and corner bonding gap between the tightly arranged NCs; this endows the substrate with benign sensitivity and reproducibility and has great potential in molecular detection, biosensing, and food safety monitoring.

Gelucire®-mediated heterometallic AgAu nanohybrid engineering for femtomolar cysteine detection using smartphone-based plasmonics technology

Conventionally nanoparticles (NPs) are synthesized using reducing and capping agents that are often hazardous for the environment and are not economically viable. Consequently, there is a growing requirement of bio-friendly methodologies for nanosynthesis via the green chemistry approach. The present study discusses the frugal and cost effective one-pot synthesis of AgAu nanohybrid exploiting the UV-treatment without the use of environmentally hazardous chemicals. Biocompatible pharmaceutical carrier Gelucire® has been utilized for this purpose as both the reducing agent and stabilizer. The obtained nanohybrids displayed unique nano-geometries and generated regions of augmented electromagnetic (EM) intensity ‘hotspots’ while studied on metallic thin films in reverse Kretschmann (RK) configuration. In addition to being highly beneficial from the sustainable development standpoint, the synthesized nanohybrids showcased unprecedented surface plasmon-coupled emission (SPCE) enhancement of >1000-fold and a sharply directional, p-polarized dequenched emission, on account of high EM field intensity. Furthermore, the obtained augmented SPCE enhancement was utilized for attaining femtomolar sensitivity of biologically significant amino acid cysteine using a mobile phone based plasmonics platform. Excellent correlation has been observed between the results obtained using an expensive spectrophotometer and the user-friendly mobile phone-based detector.

Radiation Characteristic Analysis of Antenna Deeply Implanted in Human Body and Localization Sensor Array

In-vivo antennas are increasingly used in human implant devices. However, the two most confusing issues, analytical solutions of radiation fields and communication frequency selection of antennas deeply implanted in human bodies, have not been studied and resolved, whereas they are both significant to antenna design, communication and localization system construction of human implant devices. Therefore, in this paper, the electromagnetic model of an antenna in a lossy multi-layered cylindrical media is established, which can more accurately simulate the human environment. The analytical solutions of electric intensity, magnetic intensity and Poynting vector are derived by solving the boundary value problem of electromagnetic fields, which have not been reported in the existing literatures. Through theoretical calculations at 433 MHz, 915 MHz and 2.45 GHz, the radiation characteristics of the antenna in the torso are analyzed, and the important results are achieved. (i)The electromagnetic fields in human body do not attenuate monotonously with the increasing of the field point distance, and multiple extreme points appear due to the influence of the reflected wave at the interface of different human tissues. (ii)The electromagnetic field intensity at the surface of human body is the largest at 915 MHz, while the induced voltage of receiving antenna outside the body is the largest at 2.45 GHz. Finally, by experiments and simulations, the analytical solutions are verified, which can provide theoretical guidance for the in-vivo antenna design, frequency selection, communication and electromagnetic localization. A localization system for human implant devices as an antenna application example is built, and it is proved that the theoretical model proposed in this paper can be used for human implant device localization.

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.