6G无线通信THz电子学、光子学、等离子体波器件及应用的新进展

移动通信技术已成为由现代智能信息网络发展带动的重要技术之一。继sub-6 GHz和毫米波频段的5G移动通信成为当今移动通信的发展主流之后,预计以亚THz/THz频段的6G移动通信将于2030年到来。综述了用于未来6G无线通信的THz电子学、光子学、等离子体波器件及应用的新进展。综述并分析了当今THz器件与电路以及典型应用的关键技术的发展现状与趋势,包含真空电子领域的行波管、碰撞雪崩渡越时间(IMPATT)二极管、THz谐振隧穿二极管(RTD)、THz肖特基势垒二极管(SBD)、THz CMOS、THz SiGe BiCMOS、THz InP HEMT/InP HBT、D波段GaN HEMT、光子学辅助的太赫兹波技术、石墨烯为代表的二维材料器件与电路。THz器件的应用创新重点包含四个方面:通道测量与建模、多输入多输出(MIMO)天线阵列、智能可重构反射阵列以及通信局域网络架构和实验平台。

A new horizon for neuroscience:terahertz biotechnology in brain research

Terahertz biotechnology has been increasingly applied in various biomedical fields and has especially shown great potential for application in brain sciences.In this article,we review the development of terahertz biotechnology and its applications in the field of neuropsychiatry.Available evidence indicates promising prospects for the use of terahertz spectroscopy and terahertz imaging techniques in the diagnosis of amyloid disease,cerebrovascular disease,glioma,psychiatric disease,traumatic brain injury,and myelin deficit.In vitro and animal experiments have also demonstrated the potential therapeutic value of terahertz technology in some neuropsychiatric diseases.Although the precise underlying mechanism of the interactions between terahertz electromagnetic waves and the biosystem is not yet fully understood,the research progress in this field shows great potential for biomedical noninvasive diagnostic and therapeutic applications.However,the biosafety of terahertz radiation requires further exploration regarding its two-sided efficacy in practical applications.This review demonstrates that terahertz biotechnology has the potential to be a promising method in the field of neuropsychiatry based on its unique advantages.

Terahertz toroidal dipole metamaterial sensors for detection of aflatoxin B1

Terahertz metamaterial biosensors have attracted significant attention in the biological field due to their advantages of label-free,real-time and in situ detection.In this paper,a highly sensitive metamaterial sensor with semi-ring mirror symmetry based on toroidal dipole resonance is designed for a new metamaterial biosensor.It is shown that a refractive index sensitivity of 337.5 GHz per refractive index unit can be achieved under an analyte of saturated thickness near a 1.33 THz transmission dip.For biosensor samples where aflatoxin B1 is dropped on the metamaterial surface in our experiment,dip amplitudes of transmission varying from 0.1904 to 0.203 and 0.2093 are observed as aflatoxin B1 concentrations are altered from 0 to 0.001μg·ml-1 and to 0.01μg·ml-1,respectively.Furthermore,when aflatoxin B1 concentrations are 0.1μg·ml-1,1μg·ml-1,10μg·ml-1 and 100μg·ml-1,dip amplitudes of 0.2179,0.226,0.2384 and 0.2527 and dip redshifts of 10.1 GHz,20.1 GHz,27.7 GHz and 37.6 GHz are respectively observed.These results illustrate high-sensitivity,label-free detection of aflatoxin B1,enriching the applications of sensors in the terahertz domain.

High photoelectric conversion efficiency and fast relaxation time of FA_(0.4)MA_(0.6)PbI_(3) applied in ultrafast modulation of terahertz waves

Active control of terahertz(THz)waves is attracting tremendous attentions in terahertz communications and active photonic devices.Perovskite,due to its excellent photoelectric conversion performance and simple manufacturing process,has emerged as a promising candidate for optoelectronic applications.However,the exploration of perovskites in optically controlled THz modulators is still limited.In this work,the photoelectric properties and carrier dynamics of FA_(0.4)MA_(0.6)PbI_(3)perovskite films were investigated by optical pumped terahertz probe(OPTP)system.The ultrafast carrier dynamics reveal that FA_(0.4)MA_(0.6)PbI_(3)thin film exhibits rapid switching and relaxation time within picosecond level,suggesting that FA_(0.4)MA_(0.6)PbI_(3)is an ideal candidate for active THz devices with ultrafast response.Furthermore,as a proof of concept,a FA_(0.4)MA_(0.6)PbI_(3)-based metadevice with integrating plasma-induced transparency(PIT)effect was fabricated to achieve ultrafast modulation of THz wave.The experimental results demonstrated that the switching time of FA_(0.4)MA_(0.6)PbI_(3)-based THz modulator is near to 3.5 ps,and the threshold of optical pump is as low as 12.7μJ cm^(-2).The simulation results attribute the mechanism of ultrafast THz modulation to photo-induced free carriers in the FA_(0.4)MA_(0.6)PbI_(3)layer,which progressively shorten the capacitive gap of PIT resonator.This study not only illuminates the potential of FA_(0.4)MA_(0.6)PbI_(3)in THz modulation,but also contributes to the field of ultrafast photonic devices.

Polarimeter–interferometer diagnostic using terahertz solid-state sources for fluctuation measurements on Keda Torus e Xperiment(KTX)

A multi-channel polarimeter-interferometer has been developed on the Keda Torus eXperiment(KTX)for the study of equilibrium dynamics and internal magnetic fluctuations.A three-wave technique based on terahertz solid-state sources(-650 GHz)is applied for simultaneous measurements of electron density and Faraday rotation angle.The output power of the microwave source is 2 mW.Faraday rotation effect using a rotating wave plate is tested with phase noise less than 0.8°,and the density phase noise is less than 0.9°.Measurement of Faraday rotation angle and density for discharges on KTX have demonstrated high sensitivity to internal MHD activities.

基于CW-THz的防热瓦结构缺陷深度检测校正方法

太赫兹探测成像技术在航空航天无损检测领域具有重要应用前景,采用无损检测方法对热防护材料进行相关检测,对保证材料质量以及提高其使用可靠性等都具有重要意义。因调频连续太赫兹采集信号受系统工作带宽的限制导致测试精度低,为提高其测量精度,本文引入不同的离散频谱校正与细化方法进行比较分析。以热防护结构的陶瓷防热瓦为研究对象,对防热瓦中不同深度的孔洞缺陷进行检测,通过分析样件的太赫兹二维图像以及典型信号对比,获取缺陷的位置和大小信息,从信号处理的角度进行深度信息校正。结果表明,调频连续太赫兹检测系统可以清晰识别热防护结构中的孔洞缺陷,且离散频谱细化及校正处理算法能较准确的定位缺陷深度,其校正误差在1 mm范围内。

Phase-locked single-mode terahertz quantum cascade lasers array

We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs)array,with a single-mode pulse power of 108 mW at 13 K.The device utilizes a Talbot cavity to achieve phase locking among five ridge lasers with first-order buried distributed feedback(DFB)grating,resulting in nearly five times amplification of the single-mode power.Due to the optimum length of Talbot cavity depends on wavelength,the combination of Talbot cavity with the DFB grating leads to better power amplification than the combination with multimode Fabry-Perot(F-P)cavities.The Talbot cavity facet reflects light back to the ridge array direction and achieves self-imaging in the array,enabling phase-locked operation of ridges.We set the spacing between adjacent elements to be 220μm,much larger than the free-space wavelength,ensuring the operation of the fundamental supermode throughout the laser's dynamic range and obtaining a high-brightness far-field distribution.This scheme provides a new approach for enhancing the single-mode power of THz QCLs.

Ultrafast carrier dynamics in GeSn thin film based on time-resolved terahertz spectroscopy

We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn under femtosecond laser excitation at 2500 nm,and its pump-induced photoconductivity can be explained by the Drude–Smith model.The carrier recombination process is mainly dominated by defect-assisted Auger processes and defect capture.The firstand second-order recombination rates are obtained by the rate equation fitting,which are(2.6±1.1)×10^(-2)ps^(-1)and(6.6±1.8)×10^(-19)cm^(3)·ps^(-1),respectively.Meanwhile,we also obtain the diffusion length of photo-generated carriers in GeSn,which is about 0.4μm,and it changes with the pump delay time.These results are important for the GeSn-based infrared optoelectronic devices,and demonstrate that Ge Sn materials can be applied to high-speed optoelectronic detectors and other applications.

Terahertz high-sensitivity SIS mixer based on Nb–AlN–NbN hybrid superconducting tunnel junctions

The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environments that support life and imaging black holes.High-sensitivity superconductor–insulator–superconductor(SIS)mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays.Compared to the commonly used classical Nb/AlO_(x)/Nb superconducting tunnel junction,the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density.This makes it particularly promising for the development of ultra-wideband,high-sensitivity coherent detectors or mixers in various scientific research fields.In this paper,we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions(PCTJ),which has a bandwidth extending up to490 GHz–720 GHz.The best achieved double-sideband(DSB)noise temperature(sensitivity)is below three times the quantum noise level.

Terahertz quasi-perfect vortex beam with integer-order and fractional-order generated by spiral spherical harmonic axicon

We propose a new method to generate terahertz perfect vortex beam with integer-order and fractional-order. A new optical diffractive element composed of the phase combination of a spherical harmonic axicon and a spiral phase plate is designed and called spiral spherical harmonic axicon. A terahertz Gaussian beam passes through the spiral spherical harmonic axicon to generate a terahertz vortex beam. When only the topological charge number carried by spiral spherical harmonic axicon increases, the ring radius of terahertz vortex beam increases slightly, so the beam is shaped into a terahertz quasi-perfect vortex beam. Importantly, the terahertz quasi-perfect vortex beam can carry not only integer-order topological charge number but also fractional-order topological charge number. This is the first time that vortex beam and quasi-perfect vortex beam with fractional-order have been successfully realized in terahertz domain and experiment.

Channel Estimation for Reconfigurable Intelligent Surface Aided Multiuser Millimeter-Wave/THz Systems

It is assumed that reconfigurable intelligent surface(RIS)is a key technology to enable the potential of mmWave communications.The passivity of the RIS makes channel estimation difficult because the channel can only be measured at the transceiver and not at the RIS.In this paper,we propose a novel separate channel estimator via exploiting the cascaded sparsity in the continuously valued angular domain of the cascaded channel for the RIS-enabled millimeter-wave/Tera-Hz systems,i.e.,the two-stage estimation method where the cascaded channel is separated into the base station(BS)-RIS and the RIS-user(UE)ones.Specifically,we first reveal the cascaded sparsity,i.e.,the sparsity exists in the hybrid angular domains of BS-RIS and the RIS-UEs separated channels,to construct the specific sparsity structure for RIS enabled multi-user systems.Then,we formulate the channel estimation problem using atomic norm minimization(ANM)to enhance the proposed sparsity structure in the continuous angular domains,where a low-complexity channel estimator via Alternating Direction Method of Multipliers(ADMM)is proposed.Simulation findings demonstrate that the proposed channel estimator outperforms the current state-of-the-arts in terms of performance.

CDK7抑制剂THZ1对膀胱癌5637细胞系增殖和凋亡的影响

目的 探究细胞周期依赖性激酶7(cyclin-dependent kinase 7,CDK7)抑制剂THZ1对膀胱癌5637细胞系增殖和凋亡的影响。方法 采用CCK8实验检测细胞的药物毒性情况,筛选有效药物浓度。采用平板克隆实验评估其在体外的抗肿瘤活性,研究其在一定剂量浓度内对肿瘤细胞的增殖能力的抑制作用。采用划痕实验测定药物对肿瘤细胞迁移能力的影响。采用Western blot实验检测凋亡蛋白的表达水平。结果 CCK8结果显示CDK7抑制剂THZ1对膀胱癌5637细胞系增殖能力具有抑制作用(P<0.05)。平板克隆实验显示CDK7抑制剂THZ1对膀胱癌5637细胞系的增殖能力有抑制作用(P均<0.05)。划痕实验显示CDK7抑制剂THZ1对膀胱癌5637细胞系的迁移能力有抑制作用(P均<0.05)。Western blot实验显示CDK7抑制剂THZ1对膀胱癌5637细胞系的蛋白表达水平有抑制作用(P均<0.05)。结论 CDK7抑制剂THZ1对膀胱癌5637细胞系增殖有抑制作用、促进凋亡作用,该项研究结果提示CDK7抑制剂THZ1对膀胱癌有治疗效果。

High-Order Spatial FDTD Solver of Maxwell’s Equations for Terahertz Radiation Production

We applied a spatial high-order finite-difference-time-domain (HO-FDTD) scheme to solve 2D Maxwell’s equations in order to develop a fluid model employed to study the production of terahertz radiation by the filamentation of two femtosecond lasers in air plasma. We examined the performance of the applied scheme, in this context, we implemented the developed model to study selected phenomena in terahertz radiation production, such as the excitation energy and conversion efficiency of the produced THz radiation, in addition to the influence of the pulse chirping on properties of the produced radiation. The obtained numerical results have clarified that the applied HO-FDTD scheme is precisely accurate to solve Maxwell’s equations and sufficiently valid to study the production of terahertz radiation by the filamentation of two femtosecond lasers in air plasma.

基于THz-TDS的氟橡胶材料寿命预测方法

氟橡胶(FKM)材料具有优异的耐热性、耐腐蚀性、耐油性,已成为航空、航天、石油、机械等领域的热门材料。但由于传统的FKM材料寿命检测方法存在离线检测、会损伤待测材料、检测步骤繁琐、检测效率低等缺点,目前在FKM材料实际应用中往往采用定期更换的办法,易造成材料浪费与经济损失。提出了一种基于太赫兹时域光谱检测技术(THz-TDS)的FKM材料使用寿命预测新方法。首先,通过对在热空气老化箱中经不同温度、不同时长热氧老化处理的FKM材料进行THz-TDS透射检测,获得其对应的时域光谱图,提取相应的电流峰峰值,即在一个透射采样周期中最大的探测电流值与最小的探测电流值之间的差值;再将不同老化温度的FKM材料的THz时域波形的峰峰值与老化时间进行拟合,发现FKM样品时域光谱的峰峰值随着老化时间的延长呈下降趋势,且老化温度越高该下降趋势越明显。在200、300和360℃这三个老化温度下的拟合直线的相关系数分别高达0.9734、0.9821和0.9935。其次,根据阿伦尼乌斯公式的基本思想,建立起以时域光谱峰峰值为参考标准的FKM材料寿命预测数学模型。利用时域光谱峰峰值的FKM材料使用寿命预估办法获得的老化反应速率常数的对数与老化温度倒数关系拟合直线的相关系数达0.9969。最后,采用力学拉伸测量FKM材料断裂伸长率的办法,对其基于THz-TDS的使用寿命预估数学模型中的THz-TDS峰峰值失效临界值进行验证,可得构建的基于THz-TDS的FKM材料使用寿命预估模型成立且正确。研究结果表明:将THz-TDS检测方法应用到FKM材料寿命检测具有较高的准确性,且该方法具有无损、高效、操作简便、适用性广等优点,为FKM材料制品在线检测和寿命预测提供可能性,也为其他非极性材料和电介质材料的寿命预测方法研究提供参考。

Terahertz Spectroscopic Study of Standard Substances for Bituminous Coal and Anthracite

This study underscores the significance of online monitoring of standard substances for bituminous coal and anthracite,two commonly used fossil fuels.Terahertz technology emerges as a powerful non-destructive detection method capable of revealing the physical and chemical properties of measured objects.In this research,terahertz time-domain spectroscopy technology was employed to investigate the spectral characteristics of four distinct types of bituminous coal and anthracite samples.The refractive index and absorption coefficient spectra of these samples were calculated across a frequency range of 0.5 THz to 2.5 THz.Furthermore,principal component analysis was conducted using all refractive index and absorption coefficient data within this frequency band.Through the analysis and comparison with known parameters of coal standard materials,it was established that carbon content primarily influences the refractive index of bituminous coal and anthracite,while ash content predominantly affects the absorption effect.These findings underscore the potential of terahertz spectroscopy in conjunction with principal component analysis to qualitatively assess the similarities and differences between coal samples,thus offering novel insights for the online monitoring of diverse coal types and qualities.

Research on Detection of Food additives Based on Terahertz Spectroscopy and Analytic Hierarchy Process

Terahertz time-domain spectroscopy is a kind of far-infrared spectroscopy technology,and its spectrum reflects the internal properties of substances with rich physical and chemical information,so the use of terahertz waves can be used to qualitatively identify food additives containing nitrogen elements.Analytic hierarchy process(AHP)was originally used to solve evaluation-type problems,and this paper introduces it into the field of terahertz spectral qualitative analysis,proposes a terahertz time-domain spectral qualitative identification method combined with analytic hierarchy process,and verifies the feasibility of the method by taking four common food additives(xylitol,L-alanine,sorbic acid,and benzoic acid)and two illegal additives(melamine,and Sudan Red No.I)as the objects of study.Firstly,the collected terahertz time-domain spectral data were pre-processed and transformed into a data set consisting of peaks,peak positions,peak numbers and overall trends;then,the data were divided into comparison and test sets,and a qualitative additive identification model incorporating analytic hierarchy process was constructed and parameter optimisation was performed.The results showed that the qualitative identification accuracies of additives based on single factors,i.e.,overall trend,peak value,peak position,and peak number,were 80.23%,70.93%,67.44%,and 40.70%,respectively,whereas the identification accuracy of the analytic hierarchy process qualitative identification method based on multi-factors could be improved to 92.44%.In addition,the fuzzy characterisation of the absorption spectrum data was binarised in the data pre-processing stage and used as the base data for the overall trend,and the recognition accuracy was improved to 94.19%by combining the fuzzy characterisation method of such data with the hierarchical analysis qualitative recognition model.The results show that it is feasible to use terahertz technology to identify different varieties of additives,and this paper constructs a hierarchical analytical qualitative model with better effect,which provides a new means for food additives detection,and the method is simple in steps,with a small demand for samples,which is suitable for the rapid detection of small samples.

反射式THz-TDS用于轨道交通典型液体安检的实验

太赫兹时域光谱(THz-TDS)技术用于轨道交通易燃易爆危险液体的安全检测,需要兼顾速度和准确率。一般在大流量人群中,因为检测速度限制,不适合直接采用实验室常用的测试指纹谱之后再与样品数据库的吸收峰位置比对的方法来精确确定样品成分信息。针对轨道交通中典型液体样品,在常温常压和正常大气湿度(25℃、60%空气湿度)条件下,测试反射式THzTDS的脉冲回波数据。建立非易燃易爆危险品、易燃易爆类、强酸类等分类数据库,结合样品光谱数据库特征,归纳了4种典型的时域脉冲谱线,即含有显著次级反射峰、微小次级反射峰、无反射峰和向下反转的次反射峰。依据太赫兹时域谱线次级反射峰的特征,结合分类识别决策模型,快速实现了综合分类判别,准确率达80%以上。

Terahertz波参量振荡器辐射THz波的理论研究

从固体的元激发理论出发,应用声子的受激散射原理,阐述通过激光抽运LiNbO3晶体产生THz波的参量过程的机理.按照Henry和Garrett的波耦合方法并考虑LiNbO3晶体对THz波的吸收损失,进行推理计算得出THz波参量增益计算式.

Terahertz磁波参量振荡器辐射THz波受温度的影响

从THz波增益、吸收系数、折射率几方面,讨论了THz电磁波参量振荡器辐射THz波受温度的影响,从而得到THz波增益随温度的升高而降低主要原因,是由于LiNbO3晶体中A1对称光学软模的拉曼活性降低所导致,这为今后太赫兹(THz)波参量振荡器的优化设计提供了参考价值。

基于THz时域反射成像技术的玉米种子淀粉分布可视化研究

为无损探究种子成分分布与种子活力变化的内在关系,以玉米种子主要成分淀粉为研究对象,将太赫兹时域反射成像技术与移动窗口相关系数法相结合,无损可视化构建不同活力程度的玉米种子淀粉空间分布图。以郑单958玉米品种为例,实验通过人工老化方式(40℃,100%RH)制备老化0、18、36、54、72 h的种子样本,采用Terapluse 4000太赫兹时域光谱仪及反射成像附件扫描获取不同老化程度的样本和纯玉米淀粉样品的太赫兹光谱图像。以16.35 cm^(-1)下THz图像为基准,采用阈值分割法精确提取种子胚乳、种胚区域,通过对比不同组织区域内THz平均吸光度可得胚乳和种胚光谱明显差异,且胚乳和淀粉纯物质在51.96 cm^(-1)附近存在明显的共同吸收峰。应用移动窗口相关系数法(窗口宽度为20,移动步长为10),逐像素点计算种子太赫兹时域光谱与纯玉米淀粉光谱的-相关系数,并根据相关系数值以及坐标信息绘制伪彩色热力图,可视化构建玉米种子淀粉分布图。实验统计5个老化阶段、6个谱区窗口的淀粉分布图中相关系数>0.8的像素点占比可得:在29.83~67.36 cm^(-1)区间内,种子胚乳和种子区域内的淀粉含量在种子活力下降过程中呈现总体下降趋势,即种子淀粉含量与活力呈现正相关关系。实验结果表明:太赫兹时域光谱反射成像技术结合移动窗口相关系数伪彩色成像分析方法可以初步实现种子活力变化过程中玉米种子淀粉空间分布特性的无损探测,该技术可为深入研究种子化学成分与其自身活力之间的制约关系,无损解析种子生命活动与自身生理生态规律变化提供崭新的视角和方法。