Integration of a field-effect-transistor terahertz detector with a diagonal horn antenna

Efficient coupling of terahertz electromagnetic wave with the active region in a terahertz detector is required to enhance the optical sensitivity. In this work, we demonstrate direct integration of a field-effect-transistor（FET） terahertz detector chip at the waveguide port of a horn antenna. Although the integration without a proper backshot is rather preliminary, the noise-equivalent power is greatly reduced from 2.7 nW/Hz^（1/2） for the bare detector chip to 76 pW/Hz^（1/2） at340 GHz. The enhancement factor of about 30 is confirmed by simulations revealing the effective increase in the energy flux density seen by the detector. The simulation further confirms the frequency response of the horn antenna and the onchip antennas. A design with the detector chip fully embedded within a waveguide cavity could be made to further enhance the coupling efficiency.

Performance enhancement of CMOS terahertz detector by drain current

In this paper, we study the effect of the drain current on terahertz detection for Si metal-oxide semiconductor fieldeffect transistors（MOSFETs） both theoretically and experimentally. The analytical model, which is based on the smallsignal equivalent circuit of MOSFETs, predicts the significant improvement of the voltage responsivity Rv with the bias current. The experiment on antennas integrated with MOSFETs agrees with the analytical model, but the Rv improvement is accompanied first by a decrease, then an increase of the low-noise equivalent power（NEP） with the applied current. We determine the tradeoff between the low-NEP and high-Rv for the current-biased detectors. As the best-case scenario, we obtained an improvement of about six times in Rv without the cost of a higher NEP. We conclude that the current supply scheme can provide high-quality signal amplification in practical CMOS terahertz detection.

The origin of distorted intensity pattern sensed by a lens and antenna coupled AlGaN/GaN-HEMT terahertz detector

Antenna-coupled field-effect-transistors(FETs) offer high sensitivity for terahertz detection. Both the magnitude and the polarity of the response signal are sensitive to the localized terahertz field under the gate. The ability of accurate sensing the intensity pattern is required for terahertz imaging systems. Here, we report artefacts in the intensity pattern of a focused terahertz beam around 1 THz by scanning a silicon-lens and antenna coupled AlGaN/GaN high-electron-mobility-transistor(HEMT) detector. The origin of the image distortion is found to be connected with one of the antenna blocks by probing the localized photocurrents as a function of the beam location and the frequency. Although the exact distortion is found with our specific antenna design, we believe similar artefacts could be commonplace in antenna-coupled FET terahertz detectors when the beam spot becomes comparable with the antenna size. To eliminate such artefacts, new antenna designs are welcomed to achieve strong asymmetry in the terahertz field distribution under the gate while maintaining a more symmetric radiation pattern for the whole antenna.

Enhancement of terahertz coupling efficiency by improved antenna design in GaN/AlGaN high electron mobility transistor detectors

An optimized micro-gated terahertz detector with novel triple resonant antenna is presented.The novel resonant antenna operates at room temperature and shows more than a 700% increase in photocurrent response compared to the conventional bowtie antenna.In finite-difference-time-domain simulations,we found the performance of the self-mixing GaN/AlGaN high electron mobility transistor detector is mainly dependent on the parameters L gs（the gap between the gate and the source/drain antenna） and L w（the gap between the source and drain antenna）.With the improved triple resonant antenna,an optimized micrometer-sized AlGaN/GaN high electron mobility transistor detector can achieve a high responsivity of 9.45×102 V/W at a frequency of 903 GHz at room temperature.

Characterization of a room temperature terahertz detector based on a GaN/AlGaN HEMT

We report on the characterization of a room temperature terahertz detector based on a GaN/AlGaN high electron mobility transistor integrated with three patch antennas.Experimental results prove that both horizontal and perpendicular electric fields are induced in the electron channel.A photocurrent is generated when the electron channel is strongly modulated by the gate voltage.Despite the large channel length and gate-source/drain distance, significant horizontal and perpendicular fields are achieved.The device is well described by the self-mixing of terahertz fields in the electron channel.The noise-equivalent power and responsivity are estimated to be 100 nW/（Hz）^（1/2） and 3 mA/ W at 292 K,respectively.No decrease in responsivity is observed up to a modulation frequency of 5 kHz. The detector performance can be further improved by engineering the source-gate-drain geometry to enhance the nonlinearity.

A High Performance Terahertz Waveguide Detector Based on a Low-Barrier Diode

A Schottky barrier diode with low-barrier is presented, based on which a terahertz waveguide detector working at 500-600 GHz is designed and fabricated. By using the InGaAs/InP material system, the feature of the low barrier is obtained which greatly improves the performance of the detector. The measured typical voltage responsivity is about 900 V/W at 50-560 OHz and is about 400 V/W at 560 600 GHz. The proposed broadband waveguide detector has the characteristics of simple structure, compact size, low cost and high performance, and can be used in a variety of applications such as imaging, moleeuIar spectroscopy and atmospheric remote sensing.

Terahertz Direct Detectors Based on Superconducting Hot Electron Bolometers with Microwave Biasing

Terahertz （THz） direct detectors based on superconducting niobium nitride （NbN） hot electron bolometers （HEBs） with microwave （MW） biasing are studied. The MW is used to bias the HEB to the optimum point and to readout the impedance changes caused by the incident THz signals. Compared with the thermal biasing method, this method would be more promising in large scale array with simple readout. The used NbN HEB has an excellent performance as heterodyne detector with the double sideband noise temperature （T N） of 403K working at 4.2K and 0.65THz. As a result, the noise equivalent power of 1.5pW/Hz 1/2 and the response time of 64ps are obtained for the direct detectors based on the NbN HEBs and working at 4.2K and 0.65THz.

基于共振隧穿二极管的太赫兹技术研究进展

共振隧穿二极管(Resonant Tunneling Diode, RTD)是一种基于量子隧穿效应的半导体器件,同时具有非线性特性和负阻特性,通过改变偏置电压可以作为太赫兹源和太赫兹探测器,在未来6G技术中通信感知一体化方面具有优势。简要总结了基于RTD实现的器件的工作原理,对基于RTD实现的太赫兹源和太赫兹探测器、太赫兹通信系统以及太赫兹雷达系统等太赫兹技术的研究进展进行介绍,并对当前存在的技术挑战和未来的发展方向进行探讨。基于RTD的太赫兹技术凭借其突出的优势,将成为未来电子器件领域重要的发展方向。

基于超表面的宽带太赫兹热释电探测器设计

为了解决传统太赫兹(THz)探测器吸收效率低,频率范围小的问题,提出将双层超表面吸收阵列结构与钽酸锂热释电探测器相贴合,构成宽带太赫兹超表面热释电探测器。采用MATLAB和CST联合仿真的优化方法对超表面结构进行按需优化;使用ANSYS对热释电探测器进行仿真分析,得到敏感层、绝热层等特征参数对太赫兹热释电探测器的温度变化率以及响应电流的影响。结果表明,采用超表面阵列结构提高了全THz波段的探测性能,凳型热释电探测器在给定条件下的平均热释电电流输出为31.52 pA。使用超表面作为吸收结构可以使热释电探测器具有连续且高效的吸波特性,为宽带太赫兹探测器的设计提供参考。

基于单个宽频CMOS探测器的太赫兹焦平面扫描成像系统

太赫兹波是介于毫米波与红外光之间的电磁波,具有强穿透性、非电离性、高瞬时带宽等特点,在安全检查、无损检测、医疗成像等领域有着广阔的应用前景。在成像系统中,探测器是至关重要的部分。本文提出了一种将不同中心频率的窄带探测器输出结合实现宽频带探测的结构,为了减少面积,这些窄带探测器采用嵌套式结构,即高频窄带探测器被依次放置在低频窄带探测器的内部,每一个窄带探测器均包括环形天线、匹配网络和场效应晶体管检波电路。该探测器由65 nm标准CMOS工艺制成,探测频率范围覆盖了100~1000 GHz。基于该宽频探测器搭建实现了太赫兹焦平面成像系统,该系统主要包括太赫兹辐射源、聚四氟乙烯(PTFE)透镜、宽频CMOS探测器等。实验结果表明,该成像系统在100 GHz、220 GHz和300 GHz频率下能够稳定成像,并且随着频率的提高,成像质量也明显提升。通过对得到的成像结果使用形态学闭运算进行优化,解决了成像中信息缺失的问题,有效地改善了成像质量。

基于PMNT晶片热释电型太赫兹探测器的设计与应用(特邀)

针对太赫兹探测器的研究现状,分析研究了现有太赫兹探测器的优缺点,并对热释电型太赫兹探测器的热释电材料和吸收材料进行研究,提出了一种基于铌镁钛酸铅(PMNT)晶片的新型太赫兹探测器的设计和制作方法。用PMNT晶片作为热释电材料,碳纳米管作为吸收材料,使用精密减薄抛光工艺和溅射电极工艺等工艺技术,完成了新型热释电太赫兹探测器的设计与制作。并利用该探测器设计了一款太赫兹功率计,经测试,该功率计在0.1~30 THz宽频段、0.5~100 m W大功率动态范围内,功率测量准确度达到了±10%,综合指标达到国际同类产品先进水平,应用效果良好。

面向6G通信的SnSe_(2)薄膜太赫兹波探测器

第六代通信(6G)技术以其宽带宽、高速传播、保密性强等优势成为了通信技术的发展方向,并计划于2028年商用。然而,由于6G波段电磁波的光子能量较低而在室温下缺乏高效的探测手段,这也成了制约6G技术发展的因素之一。近年来,低带隙纳米材料的发展,为太赫兹波检测提供了一种低成本、高灵敏度的探测手段。对大面积、高灵敏度的薄膜太赫兹波探测器进行研究,同时引入532 nm激光和强垂直磁场进行调控,研究了外场作用下的探测性能变化,得到了外场对太赫兹波的探测效果具有极其显著的提升。因此,少层和多层SnSe_(2)薄膜在外场调控下对于太赫兹波探测有明显的提升作用,这一研究也证明了,外场调控下的SnSe_(2)薄膜对6G探测技术的发展具有重要意义。

圆锥面拟合的太赫兹发散角精密测量研究

针对太赫兹(THz)光束发散角精密测量问题,以单频连续波太赫兹源为研究对象,搭建了基于圆锥面拟合的太赫兹发散角测量装置。通过研究太赫兹光束的传播模式,分析其在空间上的光强分布特性,提出将太赫兹输出光束在远场范围内视作圆锥曲面,利用太赫兹探测器采集光斑图像,根据图像的边缘点坐标构建圆锥曲面,借助间接平差对边缘点数据做预处理并进行参数迭代与圆锥面拟合计算出光束发散角数值。结果表明,被测100 GHz的太赫兹源发散角为2.73°,相对扩展不确定度为3.8%(k=2)。

Mapping an on-chip terahertz antenna by a scanning near-field probe and a fixed field-effect transistor

In the terahertz（THz） regime,the active region for a solid-state detector usually needs to be implemented accurately in the near-field region of an on-chip antenna.Mapping of the near-field strength could allow for rapid verification and optimization of new antenna/detector designs.Here,we report a proof-of-concept experiment in which the field mapping is realized by a scanning metallic probe and a fixed AlGaN/GaN field-effect transistor.Experiment results agree well with the electromagnetic-wave simulations.The results also suggest a field-effect THz detector combined with a probe tip could serve as a high sensitivity THz near-field sensor.

Progress of Terahertz Devices Based on Graphene

Graphene is a one-atom-thick planar sheet of sp2-hybridized orbital bonded honeycomb carbon crystal. Its gapless and linear energy spectra of electrons and holes lead to the unique carrier transport and optical properties, such as giant carrier mobility and broadband flat optical response. As a novel material, graphene has been regarded to be extremely suitable and competent for the development of terahertz （THz） optical devices. In this paper, the fundamental electronic and optic properties of graphene are described. Based on the energy band structure and light transmittance properties of graphene, many novel graphene based THz devices have been proposed, including modulator, generator, detector, and imaging device. This progress has been reviewed. Future research directions of the graphene devices for THz applications are also proposed.

一种太赫兹探测器绝对光谱响应度测量方法研究

绝对光谱响应度是探测器的重要技术参数之一,随着太赫兹探测技术的发展,精确测量太赫兹探测器的绝对光谱响应度变得越来越重要。由于在太赫兹波段缺乏连续可调谐的太赫兹光源以及分光系统,因此无法采用传统测量红外探测器绝对光谱响应度的方法来实现对太赫兹探测器绝对光谱响应度的测量。基于反射法测量了2~10 THz相对光谱响应度,通过CO 2泵浦气体激光器作为泵浦光源测量了2.52和4.25 THz绝对响应度,转化得到2~10 T Hz探测器的绝对光谱响应度,并且对2.52和4.25 THz绝对响应率和相对光谱响应度这两个频率点进行了相互验证,2.52和4.25 THz绝对响应度测量值之比为0.753,相对光谱响应度测量平均值之比为0.749,两者之差仅为0.004,因此,说明本文采用的反射法测量太赫兹探测器相对光谱响应度的方法是可行的。另外水汽在太赫兹波段的测试有很大的影响,对1.5~10 THz波段大气的衰减特性进行了测试,试验表明水汽对太赫兹波有明显的衰减作用,在不同环境湿度下测量时会产生不同的结果,因此在太赫兹探测器测量过程中需要严格的控制大气的湿度,从测试数据可得到,大气中的湿度越小越好。特别是在3.3 THz波段之前,由于本身的信号比较弱,如果水汽过大或测试过程中变化较大,将严重影响测试效果。该系统可以满足太赫兹探测器的研制、生产、检测和应用,它可以为材料的选取、工艺改进、数据补偿、光学系统设计、图像处理提供指导,同时也可以推动太赫兹武器装备效能的重要依据。因此,太赫兹探测器绝对光谱响应度的测量对器件设计制造者、成像装备系统设计制造者以及器件使用者来说都具有非常重要的指导意义。

液晶太赫兹光子学研究进展

液晶作为液态和固态之间的中间态,具有液体的流动性和晶体的各向异性,其指向矢灵活可调,从微波到紫外都有广泛应用。近年来液晶光子学在太赫兹波段展现出巨大应用前景,本文综述了基于液晶的太赫兹源、可调太赫兹器件和太赫兹探测器的研究进展,探讨了未来液晶太赫兹光子学的发展趋势,如新型铁电向列相、液晶拓扑在太赫兹领域的应用,多模式、多参量的太赫兹波按需产生、调制与探测等。

红外-太赫兹光电探测器应用及前沿变革趋势

自红外辐射被发现以来,科学家一直在努力将红外技术应用于地球观测、航天遥感和宇宙探索等领域。目前,第二、三代红外探测器已进入大规模应用,高端三代也在逐步突破,并随着材料制备技术、纳米加工技术、集成技术和相关交叉学科的发展,开始出现了具有前瞻性的新材料、新技术和新概念。红外-太赫兹探测器也开始由单一探测、被动探测和探测分立的传统探测器形式,逐渐走向多维探测、自主探测和智能化芯片集成的变革发展方向。在介绍光电探测器物理机制的基础上,概述了红外-太赫兹探测技术在天文遥感领域的应用与发展,重点综述了红外-太赫兹探测器有望出现变革式发展的三大方向,包括基于人工微结构的光场集成、基于三维堆叠技术的片上智能化和新型低维材料的应用,并展望了未来探测器向着超高性能、多维感知、智能化和感存算一体化的发展趋势。

圆环孔阵列超材料对热释电太赫兹探测器性能影响关系研究

本文提出了新的基于圆环孔阵列超材料的钽酸锂热释电太赫兹探测器,以提高0.1—1 THz频段太赫兹波探测性能.仿真分析了内外径、周期、厚度等特征参数对圆环孔阵列超材料太赫兹波透射带宽及透射率的定量影响关系,阐明了圆环孔阵列超材料与热释电探测器的不同结合方式对探测器的带宽及噪声等效功率的作用机理;制备了两种圆环孔阵列超材料钽酸锂热释电太赫兹探测器;测试了圆环孔阵列超材料的透射特性和两类热释电探测器的噪声等效功率.结果表明,所制备的圆环孔阵列超材料在0.25—0.65 THz频段透射率大于40%,实现了带通滤波.当圆孔阵列超材料与热释电探测器保持足够间距时,在0.315 THz点频其噪声等效功率为11.29μW/Hz0.5,是带通波段外0.1 THz噪声等效功率的6.3%,实现了带通探测;当圆环孔阵列超材料与热释电探测器贴合时,在0.315 THz点频其噪声等效功率为4.64μW/Hz0.5,是无圆环孔阵列超材料探测器噪声等效功率的29.4%,实现了窄带探测.上述结论可用于生物成像、大分子探测等领域中特定太赫兹波段的带通与窄带探测.

集成AlGaN/GaN HEMT混频探测器的太赫兹矢量测量系统

矢量测量是表征太赫兹波段天线与准光系统波束特性的主流技术。该文介绍了一种基于AlGaN/GaN高电子迁移率晶体管(High-electron-mobility transistor, HEMT)混频探测器的太赫兹矢量测量系统。该系统核心器件为以准光-波导为耦合方式的高灵敏度太赫兹混频探测器,在340 GHz频率外差模式下,其噪声等效功率达-113 dBm/Hz。为了抑制系统相位噪声,搭建了基于二次下变频原理的硬件电路。通过对固定位置天线的长时间测量,表明系统相位稳定度优于4°,系统最小可测功率达到119 nW。基于相干AlGaN/GaN HEMT混频探测器实现了太赫兹连续波幅度和相位分布测量,该工作为后续阵列化太赫兹矢量测量提供了基础。