A High-Sensitivity Terahertz Detector Based on a Low-Barrier Schottky Diode

A low-barrier Schottky barrier diode based on the InGaAs/InP material system is designed and fabricated with a new non-destructive dry over-etching process. By using this diode, a high-sensitivity waveguide detector is proposed. The measured maximum responsivity is over 2000 mV/mW at 630 GHz. The measured noise effective power(NEP) is less than 35 pW/Hz~(0.5) at 570-630 GHz. The minimum NEP is 14 pW/Hz~(0.5) at 630 GHz. The proposed high-sensitivity 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, molecular spectroscopy and atmospheric remote sensing.     

二维电子气等离激元太赫兹波器件

固态等离激元太赫兹波器件正成为微波毫米波电子器件技术和半导体激光器技术向太赫兹波段发展和融合的重要方向之一。本综述介绍AlGaN/GaN异质结高浓度和高迁移率二维电子气中的等离激元调控、激发及其在太赫兹波探测器、调制器和光源中应用的近期研究进展。通过光栅和太赫兹天线实现自由空间太赫兹波与二维电子气等离激元的耦合,通过太赫兹法布里-珀罗谐振腔进一步调制太赫兹波模式,增强太赫兹波与等离激元的耦合强度。在光栅-谐振腔耦合的二维电子气中验证了场效应栅控的等离激元色散关系,实现了等离激元模式与太赫兹波腔模强耦合产生的等离极化激元模式,演示了太赫兹波的调制和发射。在太赫兹天线耦合二维电子气中实现了等离激元共振与非共振的太赫兹波探测,建立了太赫兹场效应混频探测的物理模型,指导了室温高灵敏度自混频探测器的设计与优化。研究表明,基于非共振等离激元激发可发展形成室温高速高灵敏度的太赫兹探测器及其焦平面阵列技术。然而,固态等离激元的高损耗特性仍是制约基于等离激元共振的高效太赫兹光源和调制器的主要瓶颈。未来的研究重点将围绕高品质因子等离激元谐振腔的构筑,包括固态等离激元物理、等离激元谐振腔边界的调控、新型室温高迁移率二维电子材料的运用和高品质太赫兹谐振腔与等离激元器件的集成等。     

基于光子集成芯片的可穿戴光纤光栅解调研究

为了实现光纤光栅传感器在可穿戴系统中的应用,提出了一种基于硅基光子集成芯片的可穿戴光纤光栅传感解调系统。基于比利时iSiPP50G工艺的光子集成芯片由4×1长波长VCSEL阵列、1×8阵列波导光栅、2×2 MMI耦合器、4×1光纤光栅耦合器阵列、Ge-on-Si波导光电探测器、直波导和弯曲波导等组成。在完成对VCSEL光源金线键合和光子集成芯片光纤耦合封装的基础上,设计了手环式解调电路,对人体温度和心音信号进行了实时测量。实验结果表明:解调系统的动态波长检测范围为1 540 nm～1 560 nm,波长分辨率为0.08 pm,解调精度为5 pm,温度监测范围为35℃～42℃,误差为±0.1℃;可检测50 Hz～100 Hz频率范围内的心音信号,可识别出第一心音和第二心音,并计算出心动周期、心率、第一心音时限、第二心音时限和心力等特征参数。     

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.     

过模结构0.14 THz高功率脉冲探测器研制

基于n型硅在强电场下的热电子效应,初步研制了一种采用过模结构的0.14 THz高功率太赫兹脉冲探测器。该探测器由基模波导WR6、过渡波导、过模波导WR10, n型硅探测芯片和偏置恒流源组成。模拟分析了探测器的工作过程,给出了相对灵敏度表达式,结果表明过模探测器能很好地工作在TE10模式。合理设计了探测芯片的结构参数和加工工艺,完成了探测芯片的加工和探测器样机的制作。将探测器样机在0.14 THz相对论表面波振荡器的辐射场进行了初步的验证性实验,并与二极管检波器的测量结果进行了对比分析。结果表明:过模探测器样机的响应时间在ps量级,相对灵敏度约为0.12 kW-1,最大承受功率至少为数十W,可用于0.14 THz高功率脉冲的直接探测。     

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.     

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 at500-600 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 500-560 GHz 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,molecular spectroscopy and atmospheric remote sensing.     

基于LT-GaAs外延片的THz片上系统

太赫兹（THz）波在物质检测方面发挥着巨大的作用,是一种非常有潜力的生化传感工具。但是传统的太赫兹时域光谱系统（TDS）结构复杂,系统的集成度低,占用空间较大。所以,如何对THz波进行有效引导、实现集成化传输并得到高质量光谱就成为太赫兹光谱系统的研究热点。太赫兹片上系统是将THz的产生、传输以及探测都集成到同一芯片上,然后通过相干探测的方法获得THz时域光谱。它可以实现对多种样品的检测,尤其在对难于取样的微量样品探测方面具有广泛的应用价值。它无需光路准直,操作简便,成品率高。两个研究工作都是基于低温砷化镓(LT-GaAs)外延片开展的。首先将一根直径为200 μm的铜线固定在LT-GaAs外延片的上方,通过真空蒸镀的方法制备出天线电极,同时得到天线间隙,研制出基于LT-GaAs外延片的THz天线。利用波长为800 nm的飞秒激光对其进行测试,得到了质量较高的THz信号,验证了天线的实用性。然后在另一外延片上利用光刻微加工工艺制作出传输线和微电极,得到了集成的THz片上系统。使用波长为1 550 nm的飞秒激光分别激发片上系统的太赫兹产生天线和探测天线,天线产生的太赫兹波在传输线上传播,在探测端同样得到了质量较高的THz时域信号,证实了THz片上系统的可行性。该方法省去了腐蚀牺牲层以及LT-GaAs薄膜的转移、键合等步骤,极大地提高了片上系统的成品率,避免了薄膜转移过程中易破碎及腐蚀液存在毒性的问题。最后,研究了外加电压对从片上系统中获得的THz波性能的影响,结果为电压越高,THz波的信号强度越强;另外,通过在传输线上方垂直放置铜箔的方法验证了THz波沿着传输线传播的事实。该研究中采用的基于LT-GaAs外延片的片上系统的制备方法简单,制作周期短,制作过程安全,应用领域广泛,这为将来与微流控芯片相结合实现对液体样品的探测打下了基础。     

A novel integrated MEMS helix antenna for terahertz applications

This paper reports the design and analysis of a novel helix antenna based on Micro-electromechanical Systems (MEMS) technology, which is used in terahertz (THz) applications. The structure of the antenna includes two parts, the metallic helix and the coplanar waveguide (CPW) on the substrate for feed, the fabrication of the structure needs only one wafer, and the antenna can be easily integrated with other parts of on-chip circuits. There are many tunable parameters of the helix, so that high performance THz antenna can be achieved by optimizing these parameters. The proposed antenna can be manufactured by MEMS processing with low fabrication cost, suitable for many terahertz systems.     

径向双层介质加载圆波导的TE_(11)-HE_(11)模式转换天线

介绍了径向双层介质加载圆波导的TE_(11)-HE_(11)模式转换天线的设计原理、实验方法及结果。该模式转换天线由圆波导TE_(11)-HE_(11)模式转换器和辐射器组成:圆波导TE_(11)-HE_(11)模式转换器是在圆波导内沿径向加载两种不同介电常数的微波介质来完成模式转换,辐射器采用开口圆波导或小张角圆锥喇叭将HE_(11)模辐射出去。应用HFSS软件对设计的两种模式转换天线进行模拟优化,数值结果显示这两种天线在线极化和圆极化工作状态下其E面、H面辐射方向图在一定波瓣宽度内均具有较高的等化特性及低副瓣电平。应用矢量网络分析仪和频谱分析仪对线极化TE11模激励状态下的两种模式转换天线的增益和驻波系数进行测试,测试结果表明:在中心频率9.4GHz频点辐射器采用开口圆波导或小张角圆锥喇叭时天线增益分别为11.21dB和15.58dB,且驻波系数均小于1.05。实测结果与仿真结果基本一致,证明了该模式转换天线技术的可行性与正确性。     

辐射式核电磁脉冲模拟器TEM喇叭天线

针对辐射式核电磁脉冲模拟器采用TEM喇叭天线作为辐射天线时低频辐射能力有限的问题,对板型和线型两种基本形式的TEM喇叭天线进行了分析。在采用线型TEM喇叭天线以减轻模拟器重量的基础上,在天线末端采用螺旋线结构,并增加屏蔽板回路,构造了一种新型TEM喇叭天线。结果表明:与普通线型TEM喇叭天线相比,该新型天线较大地提高了低频辐射性能,可使近场波形脉宽提高7ns左右,峰值场强提高了1kV/m左右;通过增大螺旋线半径和提高螺旋线密度可以提高峰值场强,增加近场波形脉宽;通过屏蔽板回路可以降低反射波纹的波峰从而改善近场波形。     

1.55μmSi_(1-x)Ge_x光波导与Si_(1-x)Ge_x/Si多量子阱探测器集成的优化设计

对１．５５μｍ波长的Ｓｉ１－ｘＧｅｘ光波导和Ｓｉ１－ｘＧｅｘ／Ｓｉ多量子阱（ＭＱＷ）红外探测器的集成器件结构进行了系统的分析和优化设计。优化结果为：１）对Ｓｉ１－ｘＧｅｘ光波导，Ｇｅ含量ｘ＝０．０５，脊宽、高和腐蚀深度分别为８、３和２．６μｍ；２）对Ｓｉ１－ｘＧｅｘ／Ｓｉ多量子阱红外探测器，Ｇｅ含量ｘ＝０．５，探测器由厚度为５５０ｎｍ、２３个周期的６ｎｍＳｉ０．５Ｇｅ０．５＋１７ｎｍＳｉ组成，长度约２ｍｍ。结果表明，这种结构器件的内量子效率可达８８％。     

A monolithic resonant terahertz sensor element comprising a metamaterial absorber and micro‐bolometer

In this article a monolithic resonant terahertz sensor element with a noise equivalent power superior to that of typical commercial room temperature single pixel terahertz detectors and capable of close to real time read‐out rates is presented. The detector is constructed via the integration of a metamaterial absorber and a micro‐bolometer sensor. An absorption magnitude of 57% at 2.5 THz, a minimum NEP of and a thermal time constant of 68 ms for the sensor are measured. As a demonstration of detector capability, it is employed in a practical Nipkow terahertz imaging system. The monolithic resonant terahertz detector is readily scaled to focal plane array formats by adding standard read‐out and addressing circuitry enabling compact, low‐cost terahertz imaging.     

Photonic-chip-based tunable slow and fast light via stimulated Brillouin scattering

We report the first (to our knowledge) demonstration of photonic chip based tunable slow and fast light via stimulated Brillouin scattering. Slow, fast, and negative group velocities were observed in a 7 cm long chalcogenide (As(2)S(3)) rib waveguide with a group index change ranging from ~-44 to +130, which results in a maximum delay of ~23 ns at a relatively low gain of ~23 dB. Demonstration of large tunable delays in a chip scale device opens up applications such as frequency sensing and true-time delay for a phased array antenna, where integration and delays ~10 ns are highly desirable.     

太赫兹片上系统中低温砷化镓薄膜光电导天线的研究

太赫兹时域光谱技术是一种在太赫兹频段内,广泛应用的光谱测量技术。这种技术可以用于许多物质的频谱分析,对于研究化学、半导体与生物分子等领域有着无可比拟的作用。然而用该系统进行样品探测时,受回波的影响频谱分辨率较低;受太赫兹波光斑大小以及待测样品与电磁波相互作用距离长短的影响,样品消耗量较多,并且整个系统的占用空间较大,这些局限性都限制了太赫兹时域光谱系统的进一步发展。为了突破太赫兹时域光谱系统的局限性,设计了一种将太赫兹泵浦区、探测区和传输波导集成到一个硅片上的太赫兹片上系统,该系统不仅能够解决上述系统的局限性,还能够省去样品测量前的光路准直环节,使样品的测量过程更加简便,同时集成化的系统也很大程度上提高了太赫兹波传输的稳定性。在太赫兹片上系统中,泵浦区和探测区的光电导天线是由低温砷化镓和金属电极制成,由于受到太赫兹片上系统的高度集成化和低温砷化镓晶体生长条件的限制,如何制备出低温砷化镓半导体薄膜衬底,并将其转移与键合,是太赫兹片上系统研制过程中的关键环节。首先利用分子束外延（MBE）技术制备出由半绝缘砷化镓、砷化镓缓冲层、砷化铝牺牲层和低温砷化镓层构成的外延片,然后利用盐酸溶液与砷化铝和低温砷化镓反应速度差别较大的原理,将200 nm厚的AlAs牺牲层腐蚀掉,从而得到2 μm厚的低温砷化镓薄膜。为了更加高效并且完整地得到低温砷化镓薄膜,研究了盐酸溶液在不同温度和不同浓度下与AlAs牺牲层的选择性腐蚀速率的关系。给出了低温砷化镓薄膜制备过程中盐酸的最佳体积比浓度和最佳温度,即在73 ℃下13.57%的盐酸溶液中进行砷化铝牺牲层的腐蚀。相比于已有工艺,这种腐蚀方法对实验设备的要求较低并且具有较高的安全性。最后,将单层低温砷化镓薄膜转移键合至硅片上,并制成光电导天线的结构。利用飞秒激光脉冲进行激发探测到太赫兹信号。由此说明,低温砷化镓薄膜的获取、转移与键合工艺能够满足芯片级太赫兹系统的制作要求,这为太赫兹片上系统的进一步研制打下了坚实的基础。     

W波段带状注矩形单栅返波振荡器模拟研究

提出并研究了一种带状电子注矩形单栅返波振荡器。首先研究了矩形单栅慢波结构的色散特性和耦合阻抗特性,然后粒子模拟并优化设计了带状注矩形单栅高频结构,预群聚腔及输出一体化结构。研究结果表明:利用电压200kV、电压2kA、截面为24mm×0.5mm的带状电子注,驱动该矩形单栅返波振荡器,能够产生42 MW的输出功率,工作频率86GHz,效率为10.5%。     

Radiation properties of ICRF waveguide couplers

The radiation spectra of a dielectric-filled waveguide (DWG) and a folded waveguide (FWG) antenna in the ion cyclotron range of frequencies are evaluated for tokamaks with the waveguide codes, which model the coupling of the waveguide modes to the plasma waves with outward radiating boundary conditions. The codes provide a self-consistent calculation of the fields across the waveguide apertures for various antenna phasings taking into account a complete set of waveguide eigenmodes including the reflected modes and, in the case of DWG, an arbitrary orientation of the antenna to the plasma magnetic field. In the studied cases, the spectra are found to be well described by a model which is based on a simplified wave field pattern determined by the antenna aperture geometry. Comparison to the corresponding loop antenna is carried out     

2.9THz束缚态向连续态跃迁量子级联激光器研制

采用气源分子束外延技术生长了GaAs/AlGaAs束缚态向连续 态跃迁的太赫兹量子级联激光器材料, 基于半绝缘等离子体波导工艺制作了太赫兹量子级联激光器. 测量了激光器的发射光谱和功率-电流-电压关系曲线, 研究了器件的激光特性. 器件激射频率约2.95 THz, 脉冲模式下, 最高工作温度为67 K. 连续波模式下, 阈值电流密度最低为230 A/cm², 最大光输出功率1.2 mW, 最高工作温度为30 K. 关键词： 太赫兹 量子级联激光器 分子束外延 波导     

利用3D打印技术制备太赫兹器件

高性能的太赫兹器件在控制太赫兹波方面起到重要的作用,因此寻求一种简单有效的太赫兹器件加工方案非常必要。本文以太赫兹波导和太赫兹滤波器为例,分别选用Kagome型光子晶体结构的波导和一维光子晶体结构的滤波器,运用商用的3D打印机加工样品,并采用透射式太赫兹时域光谱系统对样品的参数进行测量。实验结果表明:加工的波导在0.2~1.0 THz范围内传输损耗平均值约为0.02 cm~(-1),最小值可达到0.002 cm~(-1),且可运用机械拼接的方式将多个波导进行简单的连接从而获得更长的波导而不引起严重的损耗;滤波器的透射谱在0.1~0.5 THz之间有两个明显高损耗带;这两组实验结果均与理论预计非常接近。本文运用太赫兹波导和滤波器的实例证实了3D打印技术加工太赫兹器件的可行性,将会成为获取性能可控、价格低廉的太赫兹器件的有效途径。