Content of ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS in our journal

Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For selected: Download citations EndNote Ris BibTeX Toggle thumbnails Select Phonon dispersion relations of crystalline solids based on LAMMPS package Zhiyong Wei(魏志勇), Tianhang Qi(戚天航), Weiyu Chen(陈伟宇), and Yunfei Chen(陈云飞) Chin. Phys. B, 2021, 30 (11): 114301.   DOI: 10.1088/1674-1056/abf4c0 Abstract （623）   HTML （13）    PDF （1199KB）（147）       Knowledge map    The phonon dispersion relations of crystalline solids play an important role in determining the mechanical and thermal properties of materials. The phonon dispersion relation, as well as the vibrational density of states, is also often used as an indicator of variation of lattice thermal conductivity with the external stress, defects, etc. In this study, a simple and fast tool is proposed to acquire the phonon dispersion relation of crystalline solids based on the LAMMPS package. The theoretical details for the calculation of the phonon dispersion relation are derived mathematically and the computational flow chart is present. The tool is first used to calculate the phonon dispersion relation of graphene with two atoms in the unit cell. Then, the phonon dispersions corresponding to several potentials or force fields, which are commonly used in the LAMMPS package to modeling the graphene, are obtained to compare with that from the DFT calculation. They are further extended to evaluate the accuracy of the used potentials before the molecular dynamics simulation. The tool is also used to calculate the phonon dispersion relation of superlattice structures that contains more than one hundred of atoms in the unit cell, which predicts the phonon band gaps along the cross-plane direction. Since the phonon dispersion relation plays an important role in the physical properties of condensed matter, the proposed tool for the calculation of the phonon dispersion relation is of great significance for predicting and explaining the mechanical and thermal properties of crystalline solids. Select Non-invasive and low-artifact in vivo brain imaging by using a scanning acoustic-photoacoustic dual mode microscopy Wentian Chen(陈文天), Chao Tao(陶超), Zizhong Hu(胡仔仲), Songtao Yuan(袁松涛), Qinghuai Liu(刘庆淮), and Xiaojun Liu(刘晓峻) Chin. Phys. B, 2022, 31 (4): 044304.   DOI: 10.1088/1674-1056/ac4a6f Abstract （575）   HTML （1）    PDF （2890KB）（318）       Knowledge map    Photoacoustic imaging is a potential candidate for in vivo brain imaging, whereas, its imaging performance could be degraded by inhomogeneous multi-layered media, consisted of scalp and skull. In this work, we propose a low-artifact photoacoustic microscopy (LAPAM) scheme, which combines conventional acoustic-resolution photoacoustic microscopy with scanning acoustic microscopy to suppress the reflection artifacts induced by multi-layers. Based on similar propagation characteristics of photoacoustic signals and ultrasonic echoes, the ultrasonic echoes can be employed as the filters to suppress the reflection artifacts to obtain low-artifact photoacoustic images. Phantom experiment is used to validate the effectiveness of this method. Furthermore, LAPAM is applied for in-vivo imaging mouse brain without removing the scalp and the skull. Experimental results show that the proposed method successfully achieves the low-artifact brain image, which demonstrates the practical applicability of LAPAM. This work might improve the photoacoustic imaging quality in many biomedical applications which involve tissues with complex acoustic properties, such as brain imaging through scalp and skull. Select Microwave absorption properties regulation and bandwidth formula of oriented Y2Fe17N3-δ@SiO2/PU composite synthesized by reduction-diffusion method Hao Wang(王浩), Liang Qiao(乔亮), Zu-Ying Zheng(郑祖应), Hong-Bo Hao(郝宏波), Tao Wang(王涛), Zheng Yang(杨正), and Fa-Shen Li(李发伸) Chin. Phys. B, 2022, 31 (11): 114206.   DOI: 10.1088/1674-1056/ac81ac Abstract （571）   HTML （24）    PDF （3360KB）（374）       Knowledge map    As concepts closely related to microwave absorption properties, impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms. In this work, reduction-diffusion method was innovatively applied to synthesize rare earth alloy Y$_{2}$Fe$_{17}$. In order to regulate the electromagnetic parameters of absorbers, the Y$_{2}$Fe$_{17}$N$_{3-\delta }$ particles were coated with silica (Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$) and absorbers with different volume fractions were prepared. The relationship between impedance matching, matching thickness, and the strongest reflection loss peak (${\rm RL}_{\rm min}$) was presented obviously. Compared to the microwave absorption properties of Y$_{2}$Fe$_{17}$N$_{3-\delta }$/PU absorber, Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness, light weight, strong absorbing intensity, and broad bandwidth. Based on microwave frequency bands, the microwave absorption properties of the absorbers were analyzed and the related parameters were listed. As an important parameter related to perfect matching, reflection factor ($\sqrt {ărepsilon_{\rm r}/\mu_{\rm r}}$) was discussed combined with microwave amplitude attenuation. According to the origin and mathematical model of bandwidth, the formula of EAB (${\rm RL}<-10$ dB) was derived and simplified. The calculated bandwidths agreed well with experimental results. Select A 61-mJ, 1-kHz cryogenic Yb: YAG laser amplifier Huijun He(何会军), Jun Yu(余军), Wentao Zhu(朱文涛), Qingdian Lin(林庆典), Xiaoyang Guo(郭晓杨), Cangtao Zhou(周沧涛), and Shuangchen Ruan(阮双琛) Chin. Phys. B, 2021, 30 (12): 124206.   DOI: 10.1088/1674-1056/ac140d Abstract （531）   HTML （0）    PDF （1311KB）（114）       Knowledge map    We report a diode-pumped rod-type Yb:YAG laser amplifier operating at 1 kHz. Cryogenic cooling method was adopted to make the Yb:YAG crystal work with four-level behavior. A single-frequency fiber laser acts as the seed in an actively Q-switched Yb:YAG oscillator. The resonator delivers 5.75-mJ pulses at 1 kHz with a pulse duration of approximately 40 ns. The pulses were amplified to 61 mJ in a four-pass rod-type Yb:YAG amplifier with optical-to-optical efficiency of 24% in the main amplifier. The M2 parameter of the output laser is <1.4. Select Effect of pulse duration on generation of attosecond pulse with coherent wake emission Siyu Chen(陈思宇), Zhinan Zeng(曾志男), and Ruxin Li(李儒新) Chin. Phys. B, 2021, 30 (11): 114206.   DOI: 10.1088/1674-1056/abf4be Abstract （523）   HTML （0）    PDF （1628KB）（99）       Knowledge map    High-order harmonics and attosecond pulse generation with coherent wake emission are theoretically investigated for the effect of pulse duration and carrier envelope phase (CEP) of few-cycle laser pulse. We find that short pulse duration will cause the negative chirp for the high harmonics. When the laser pulse is shortened to a few cycles, the influence of the laser CEP on the chirp of the harmonics will also become more prominent. Select Brightening single-photon emitters by combining an ultrathin metallic antenna and a silicon quasi-BIC antenna Shangtong Jia(贾尚曈), Zhi Li(李智), and Jianjun Chen(陈建军) Chin. Phys. B, 2022, 31 (1): 014209.   DOI: 10.1088/1674-1056/ac248c Abstract （503）   HTML （0）    PDF （947KB）（113）       Knowledge map    Bright single-photon emitters (SPEs) are fundamental components in many quantum applications. However, it is difficult to simultaneously get large Purcell enhancements and quantum yields in metallic nanostructures because of the huge losses in the metallic nanostructures. Herein, we propose to combine an ultrathin metallic bowtie antenna with a silicon antenna above a metallic substrate to simultaneously get large Purcell enhancements, quantum yields, and collection efficiencies. As a result, the brightness of SPEs in the hybrid nanostructure is greatly increased. Due to the deep subwavelength field confinement (mode size $ < 10$~nm) of surface plasmons in the ultrathin metallic film (thickness $<4 $~nm), the Purcell enhancement of the metallic bowtie antenna improves by more than 25 times when the metal thickness decreases from 20~nm to 2~nm. In the hybrid nanostructures by combining an ultrathin metallic bowtie antenna with a silicon antenna, the Purcell enhancement (Fp$\,\approx 2.6\times 10^{6})$ in the hybrid nanostructures is 63 times greater than those ($\le 4.1\times 10^{4}$) in the previous metallic and hybrid nanostructures. Because of the reduced ratio of electromagnetic fields in the ultrathin metallic bowtie antenna when the high-index silicon antenna is under the quasi-BIC state, a high quantum yield (QY$\,\approx 0.70$) is obtained. Moreover, the good radiation directivity of the quasi-BIC (bound state in the continuum) mode of the silicon antenna and the reflection of the metallic substrate result in a high collection efficiency (CE$\,\approx 0.71$). Consequently, the overall enhancement factor of brightness of a SPE in the hybrid nanostructure is EF$^{\ast }\approx {\rm Fp}\times {\rm QY}\times {\rm CE}\approx 1.3\times 10^{6}$, which is $5.6\times 10^{2}$ times greater than those (EF$^{\ast }\le 2.2\times 10^{3}$) in the previous metallic and hybrid nanostructures. Select Hidden symmetry operators for asymmetric generalized quantum Rabi models Xilin Lu, Zi-Min Li, Vladimir V Mangazeev, and Murray T Batchelor Chin. Phys. B, 2022, 31 (1): 014210.   DOI: 10.1088/1674-1056/ac20c2 Abstract （499）   HTML （0）    PDF （413KB）（107）       Knowledge map    The hidden $\mathbb{Z}_2$ symmetry of the asymmetric quantum Rabi model (AQRM) has recently been revealed via a systematic construction of the underlying symmetry operator. Based on the AQRM result, we propose an ansatz for the general form of the symmetry operators for AQRM-related models. Applying this ansatz we obtain the symmetry operator for three models: the anisotropic AQRM, the asymmetric Rabi--Stark model (ARSM), and the anisotropic ARSM. Select GaSb-based type-I quantum well cascade diode lasers emitting at nearly 2-μm wavelength with digitally grown AlGaAsSb gradient layers Yi Zhang(张一), Cheng-Ao Yang(杨成奥), Jin-Ming Shang(尚金铭), Yi-Hang Chen(陈益航), Tian-Fang Wang(王天放), Yu Zhang(张宇), Ying-Qiang Xu(徐应强), Bing Liu(刘冰), and Zhi-Chuan Niu(牛智川) Chin. Phys. B, 2021, 30 (9): 094204.   DOI: 10.1088/1674-1056/abe930 Abstract （494）   HTML （2）    PDF （731KB）（71）       Knowledge map    We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength. The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector. The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper. And the quantum well cascade laser with 100-μm-wide, 2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature. The characteristic temperature T0 is estimated at above 60 K. Select Ultrafast carrier dynamics of Cu2O thin film induced by two-photon excitation Jian Liu(刘建), Jing Li(李敬), Kai-Jun Mu(牧凯军), Xin-Wei Shi(史新伟), Jun-Qiao Wang(王俊俏), Miao Mao(毛淼), Shu Chen(陈述), and Er-Jun Liang(梁二军) Chin. Phys. B, 2021, 30 (11): 114205.   DOI: 10.1088/1674-1056/ac003c Abstract （490）   HTML （0）    PDF （943KB）（227）       Knowledge map    Cuprous oxide (Cu2O) has attracted plenty of attention for potential nonlinear photonic applications due to its superior third-order nonlinear optical property such as two-photon absorption. In this paper, we investigated the two-photon excitation induced carrier dynamics of a Cu2O thin film prepared by radio-frequency magnetron sputtering, using the femtosecond transient absorption experiments. Biexponential dynamics including an ultrafast carrier scattering (< 1 ps) followed by a carrier recombination (> 50 ps) were observed. The time constant of carrier scattering under two-photon excitation is larger than that under one-photon excitation, due to the different transition selection rules and smaller absorption coefficient of the two-photon excitation. Select A broadband self-powered UV photodetector of a β-Ga2O3/γ-CuI p-n junction Wei-Ming Sun(孙伟铭), Bing-Yang Sun(孙兵阳), Shan Li(李山), Guo-Liang Ma(麻国梁), Ang Gao(高昂), Wei-Yu Jiang(江为宇), Mao-Lin Zhang(张茂林), Pei-Gang Li(李培刚), Zeng Liu(刘增), and Wei-Hua Tang(唐为华) Chin. Phys. B, 2022, 31 (2): 024205.   DOI: 10.1088/1674-1056/ac29b3 Abstract （490）   HTML （0）    PDF （1854KB）（123）       Knowledge map    The symmetric Ti/Au bi-layer point electrodes have been successfully patterned on the β-Ga2O3 films which are prepared by metal-organic chemical vapor deposition (MOCVD) and the γ-CuI films which are prepared by spin-coating. The fabricated heterojunction has a large open circuit voltage (Voc) of 0.69 V, desired for achieving self-powered operation of a photodetector. Irradiated by 254-nm ultraviolet (UV) light, when the bias voltage is -5 V, the dark current (Idark) of the device is 0.47 pA, the photocurrent (Iphoto) is -50.93 nA, and the photo-to-dark current ratio (Iphoto/Idark) reaches about 1.08×105. The device has a stable and fast response speed in different wavelengths, the rise time (τr) and decay time (τd) are 0.762 s and 1.741 s under 254-nm UV light illumination, respectively. While the τr and τd are 10.709 s and 7.241 s under 365-nm UV light illumination, respectively. The time-dependent (I-t) response (photocurrent in the order of 10-10 A) can be clearly distinguished at a small light intensity of 1 μW·cm-2. The internal physical mechanism affecting the device performances is discussed by the band diagram and charge carrier transfer theory. Select Preparation and properties of GAGG:Ce/glass composite scintillation material Wei-Jie Zhang(张伟杰), Qin-Hua Wei(魏钦华), Xiao Shen(沈潇), Gao Tang(唐高), Zhen-Hua Chen(陈振华), Lai-Shun Qin(秦来顺), and Hong-Sheng Shi(史宏声) Chin. Phys. B, 2021, 30 (7): 074205.   DOI: 10.1088/1674-1056/abe3ea Abstract （486）   HTML （4）    PDF （3833KB）（184）       Knowledge map    The translucent GGAG:Ce/glass composites are prepared successfully by ball-milling, tableting, and pressureless sintering. The thickness of composites is about 400 μm. The x-ray diffraction (XRD), differential scanning calorimetry (DSC), density of composite materials are measured and discussed systematically. The scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) elemental mapping are employed to analyze the particle size, the shape of powders, and the distribution of GGAG:Ce particles in the glass matrix, respectively. The decay time, ultraviolet, (UV), x-ray excitation luminescence spectra, and temperature spectra are studied. The results show that the composite materials have high light output, good thermostability, and short decay time. The method adopted in this work is an effective method to reduce the preparation time and cost of the sample. The ultralow afterglow indicates that the composite materials have an opportunity to be used for x-ray detection and imaging. Select Exploring fundamental laws of classical mechanics via predicting the orbits of planets based on neural networks Jian Zhang(张健), Yiming Liu(刘一鸣), and Zhanchun Tu(涂展春) Chin. Phys. B, 2022, 31 (9): 094502.   DOI: 10.1088/1674-1056/ac8d88 Abstract （484）   HTML （21）    PDF （1058KB）（112）       Knowledge map    Neural networks have provided powerful approaches to solve various scientific problems. Many of them are even difficult for human experts who are good at accessing the physical laws from experimental data. We investigate whether neural networks can assist us in exploring the fundamental laws of classical mechanics from data of planetary motion. Firstly, we predict the orbits of planets in the geocentric system using the gate recurrent unit, one of the common neural networks. We find that the precision of the prediction is obviously improved when the information of the Sun is included in the training set. This result implies that the Sun is particularly important in the geocentric system without any prior knowledge, which inspires us to gain Copernicus' heliocentric theory. Secondly, we turn to the heliocentric system and make successfully mutual predictions between the position and velocity of planets. We hold that the successful prediction is due to the existence of enough conserved quantities (such as conservations of mechanical energy and angular momentum) in the system. Our research provides a new way to explore the existence of conserved quantities in mechanics system based on neural networks. Select Broad-band phase retrieval method for transient radial shearing interference using chirp Z transform technique Fang Xue(薛芳), Ya-Xuan Duan(段亚轩), Xiao-Yi Chen(陈晓义), Ming Li(李铭), Suo-Chao Yuan(袁索超), and Zheng-Shang Da(达争尚) Chin. Phys. B, 2021, 30 (8): 084209.   DOI: 10.1088/1674-1056/abff2f Abstract （478）   HTML （0）    PDF （3328KB）（113）       Knowledge map    The transient radial shearing interferometry technique based on fast Fourier transform (FFT) provides a means for the measurement of the wavefront phase of transient light field. However, which factors affect the spatial bandwidth of the wavefront phase measurement of this technology and how to achieve high-precision measurement of the broad-band transient wavefront phase are problems that need to be studied further. To this end, a theoretical model of phase-retrieved bandwidth of radial shearing interferometry is established in this paper. The influence of the spatial carrier frequency and the calculation window on phase-retrieved bandwidth is analyzed, and the optimal carrier frequency and calculation window are obtained. On this basis, a broad-band transient radial shearing interference phase-retrieval method based on chirp Z transform (CZT) is proposed, and the corresponding algorithm is given. Through theoretical simulation, a known phase is used to generate the interferogram and it is retrieved by the traditional method and the proposed method respectively. The residual wavefront RMS of the traditional method is 0.146λ, and it is 0.037λ for the proposed method, which manifests an improvement of accuracy by an order of magnitude. At the same time, different levels of signal-to-noise ratios (SNRs) from 50 dB to 10 dB of the interferogram are simulated, and the RMS of the residual wavefront is from 0.040λ to 0.066λ. In terms of experiments, an experimental verification device based on a phase-only spatial light modulator is built, and the known phase on the modulator is retrieved from the actual interferogram. The RMS of the residual wavefront retrieved through FFT is 0.112λ, and it decreases to 0.035λ through CZT. The experimental results verify the effectiveness of the method proposed in this paper. Furthermore, the method can be used in other types of spatial carrier frequency interference, such as lateral shearing interference, rotational shearing interference, flipping shearing interference, and four-wave shearing interference. Select Monte Carlo simulations of electromagnetically induced transparency in a square lattice of Rydberg atoms Shang-Yu Zhai(翟尚宇) and Jin-Hui Wu(吴金辉) Chin. Phys. B, 2021, 30 (7): 074206.   DOI: 10.1088/1674-1056/abd75a Abstract （477）   HTML （4）    PDF （893KB）（107）       Knowledge map    We study the steady optical response of a square lattice in which all trapped atoms are driven by a probe and a coupling fields into the ladder configuration of electromagnetically induced transparency (EIT). It turns out to be a many-body problem in the presence of van der Waals (vdW) interaction among atoms in the upmost Rydberg state, so Monte Carlo (MC) calculation based on density matrix equations have been done after introducing a sufficiently large cut-off radius. It is found that the absorption and dispersion of EIT spectra depends critically on a few key parameters like lattice dimension, unitary vdW shift, probe Rabi frequency, and coupling detuning. Through modulating these parameters, it is viable to change symmetries of the absorption and dispersion spectra and control on demand depth and position of the transparency window. Our MC calculation is expected to be instructive in understanding many-body quantum coherence effects and in manipulating non-equilibrium quantum phenomena by utilizing vdW interactions of Rydberg atoms. Select All-fiber laser seeded femtosecond Yb:KGW solid state regenerative amplifier Renchong Lv(吕仁冲), Hao Teng(滕浩), Jiajun Song(宋贾俊), Renzhu Kang(康仁铸), Jiangfeng Zhu(朱江峰), and Zhiyi Wei(魏志义) Chin. Phys. B, 2021, 30 (9): 094206.   DOI: 10.1088/1674-1056/ac11d3 Abstract （477）   HTML （0）    PDF （1407KB）（258）       Knowledge map    A high efficiency compact Yb:KGW regenerative amplifier using an all-fiber laser seed source was comprehensively studied. With thermal lensing effect compensated by the cavity design, the compressed pulses with energy of 1 mJ at 1 kHz and 0.4 mJ at 10 kHz in sub-400-fs pulse duration using chirped fiber Bragg grating (CFBG) stretcher were demonstrated. A modified Frantz-Nodvik equation was developed to emulate the dynamic behavior of the regenerative amplifier. The simulation results were in good agreement with the experiment. Numerical simulations and experimental results show that the scheme can be scalable to higher energy of multi-mJ, sub-300 fs pulses. Select Broad gain, continuous-wave operation of InP-based quantum cascade laser at λ~11.8 μm Huan Wang(王欢), Jin-Chuan Zhang(张锦川), Feng-Min Cheng(程凤敏), Zeng-Hui Gu(顾增辉), Ning Zhuo(卓宁), Shen-Qiang Zhai(翟慎强), Feng-Qi Liu(刘峰奇), Jun-Qi Liu(刘俊岐), Shu-Man Liu(刘舒曼), and Zhan-Guo Wang(王占国) Chin. Phys. B, 2021, 30 (12): 124202.   DOI: 10.1088/1674-1056/abf91a Abstract （476）   HTML （1）    PDF （994KB）（180）       Knowledge map    We demonstrate a broad gain, continuous-wave (CW) operation InP-based quantum cascade laser (QCL) emitting at 11.8 μm with a modified dual-upper-state (DAU) and diagonal transition active region design. A 3 mm cavity length, 16.5 μm average ridge wide QCL with high-reflection (HR) coatings demonstrates a maximum peak power of 1.07 W at 283 K and CW output power of 60 mW at 293 K. The device also shows a broad and dual-frequency lasing spectrum in pulsed mode and a maximum average power of 258.6 mW at 283 K. Moreover, the full width at half maximum (FWHM) of the electroluminescent spectrum measured at subthreshold current is 2.37 μm, which indicates a broad gain spectrum of the materials. The tuning range of 1.38 μm is obtained by a grating-coupled external cavity (EC) Littrow configuration, which is beneficial for gas detection. Select Construction and mechanism analysis on nanoscale thermal cloak by in-situ annealing silicon carbide film Jian Zhang(张健), Hao-Chun Zhang(张昊春), Zi-Liang Huang(黄子亮), Wen-Bo Sun(孙文博), and Yi-Yi Li(李依依) Chin. Phys. B, 2022, 31 (1): 014402.   DOI: 10.1088/1674-1056/ac2809 Abstract （473）   HTML （0）    PDF （1808KB）（176）       Knowledge map    In recent years, there is a strong interest in thermal cloaking at the nanoscale, which has been achieved by using graphene and crystalline silicon films to build the nanoscale thermal cloak according to the classical macroscopic thermal cloak model. Silicon carbide, as a representative of the third-generation semiconductor material, has splendid properties, such as the high thermal conductivity and the high wear resistance. Therefore, in the present study, we build a nanoscale thermal cloak based on silicon carbide. The cloaking performance and the perturbation of the functional area to the external temperature filed are analyzed by the ratio of thermal cloaking and the response temperature, respectively. It is demonstrated that silicon carbide can also be used to build the nanoscale thermal cloak. Besides, we explore the influence of inner and outer radius on cloaking performance. Finally, the potential mechanism of the designed nanoscale thermal cloak is investigated by calculating and analyzing the phonon density of states (PDOS) and mode participation rate (MPR) within the structure. We find that the main reason for the decrease in the thermal conductivity of the functional area is phonon localization. This study extends the preparation method of nanoscale thermal cloaks and can provide a reference for the development of other nanoscale devices. Select Omnidirectional and compact Tamm phonon-polaritons enhanced mid-infrared absorber Xiaomin Hua(花小敏), Gaige Zheng(郑改革), Fenglin Xian(咸冯林), Dongdong Xu(徐董董), and Shengyao Wang(王升耀) Chin. Phys. B, 2021, 30 (8): 084202.   DOI: 10.1088/1674-1056/abe22b Abstract （472）   HTML （1）    PDF （1417KB）（151）       Knowledge map    Narrow band mid-infrared (MIR) absorption is highly desired in thermal emitter and sensing applications. We theoretically demonstrate that the perfect absorption at infrared frequencies can be achieved and controlled around the surface phonon resonance frequency of silicon carbide (SiC). The photonic heterostructure is composed of a distributed Bragg reflector (DBR)/germanium (Ge) cavity/SiC on top of a Ge substrate. Full-wave simulation results illustrate that the Tamm phonon-polaritons electric field can locally concentrate between the Ge cavity and the SiC film, contributed to the improved light-phonon interactions with an enhancement of light absorption. The structure has planar geometry and does not require nano-patterning to achieve perfect absorption of both polarizations of the incident light in a wide range of incident angles. Their absorption lines are tunable via engineering of the photon band-structure of the dielectric photonic nanostructures to achieve reversal of the geometrical phase across the interface with the plasmonic absorber. Select Low-threshold bistable reflection assisted by oscillating wave interaction with Kerr nonlinear medium Yingcong Zhang(张颖聪), Wenjuan Cai(蔡文娟), Xianping Wang(王贤平), Wen Yuan(袁文), Cheng Yin(殷澄), Jun Li(李俊), Haimei Luo(罗海梅), and Minghuang Sang(桑明煌) Chin. Phys. B, 2021, 30 (8): 084203.   DOI: 10.1088/1674-1056/abe118 Abstract （471）   HTML （1）    PDF （924KB）（75）       Knowledge map    Owing to the enormously enhanced oscillating wave, a minute variation of the incident light intensity will give rise to a change in the dielectric constant of the Kerr nonlinear medium and lead to a bistable reflection with an ultra-low threshold intensity, which is closely related to the angle of incidence and the thickness of the Kerr nonlinear medium. The criterion for the existence of optical bistability is derived. Our bistability scheme is simple and not limited to the TM-polarization. Select Fast prediction of aerodynamic noise induced by the flow around a cylinder based on deep neural network Hai-Yang Meng(孟海洋), Zi-Xiang Xu(徐自翔), Jing Yang(杨京), Bin Liang(梁彬), and Jian-Chun Cheng(程建春) Chin. Phys. B, 2022, 31 (6): 064305.   DOI: 10.1088/1674-1056/ac5e98 Abstract （465）   HTML （7）    PDF （1086KB）（346）       Knowledge map    Accurate and fast prediction of aerodynamic noise has always been a research hotspot in fluid mechanics and aeroacoustics. The conventional prediction methods based on numerical simulation often demand huge computational resources, which are difficult to balance between accuracy and efficiency. Here, we present a data-driven deep neural network (DNN) method to realize fast aerodynamic noise prediction while maintaining accuracy. The proposed deep learning method can predict the spatial distributions of aerodynamic noise information under different working conditions. Based on the large eddy simulation turbulence model and the Ffowcs Williams-Hawkings acoustic analogy theory, a dataset composed of 1216 samples is established. With reference to the deep learning method, a DNN framework is proposed to map the relationship between spatial coordinates, inlet velocity and overall sound pressure level. The root-mean-square-errors of prediction are below 0.82 dB in the test dataset, and the directivity of aerodynamic noise predicted by the DNN framework are basically consistent with the numerical simulation. This work paves a novel way for fast prediction of aerodynamic noise with high accuracy and has application potential in acoustic field prediction. page Page 1 of 24 Total 470 records First page Prev page Next page Last page