一种太赫兹探测器射频读出装置及其实现方法

本发明公开了一种能够在射频波段高速、精确检测太赫兹波信号的射频读出放大装置及其实现方法。该太赫兹探测器的射频读出装置包括太赫兹探测器和由各种射频元件组成的射频电路。本发明的特点在于设计一射频共振电路,灵敏太赫兹探测器作为射频共振电路的损耗组件;太赫兹波辐射引起探测器阻抗变化和共振幅度的相应变化,通过射频电路放大、混频、滤波后将太赫兹波探测器中的微弱电流检测转换为射频载波信号的检测。本发明充分结合射频电路和太赫兹探测器两者的优点,具有响应速度快和灵敏度高的优点,可广泛用于太赫兹成像、通信、材料物性分析和安全检测等太赫兹应用技术中

一种水合物沉积物样品制备方法

本发明公开一种水合物沉积物样品制备方法，包括：从沉积物样品的一端注入天然气，其中，进气端至出气端的沉积物样品含盐量从高到低具有梯度，和/或，进气端至出气端的沉积物样品的温度从高到低具有梯度，使得出气端的沉积物样品先形成水合物，再逐渐延伸至进气端的沉积物样品形成水合物。本发明可以通过样品进出气两端的温度或盐度梯度控制或者两种方式联合，使得水合物在出气端先合成，达到需要的水合物含量后，通过温度振荡，促进水气的自然平衡分布，这样制备含水合物沉积物方法，周期短、水合物含量可控范围广且均匀性好

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

<div id="articleAbsctract"> <p> 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 <em>L</em>_{<font size="2">gs</font>} (the gap between the gate and the source/drain antenna) and <em>L</em>_{<font size="2">w</font>} (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 <strong>&times;</strong> 10^{<font size="2">2</font>} V/W at a frequency of 903 GHz at room temperature.</p> </div

The effect of symmetry on resonant and nonresonant photoresponses in a field-effect terahertz detector

The effect of the symmetries in the terahertz (THz) field distribution and the field-effect channel on THz photoresponse is examined. Resonant excitation of cavity plasmon modes and nonresonant self-mixing of THz waves are demonstrated in a GaN/AlGaN two-dimensional electron gas with symmetrically designed nanogates, antennas, and filters. We found that the self-mixing signal can be effectively suppressed by the symmetric design and the resonant response benefits from the residual asymmetry. The findings suggest that a single detector may provide both high sensitivity from the self-mixing mechanism and spectral resolution from the resonant response by optimizing the degree of geometrical and/or electronic symmetries

A high energy density Li2S@C nanocomposite cathode with a nitrogen-doped carbon nanotube top current collector

Lithium sulfide (Li2S), with a high theoretical capacity of 1166 mA h g(-1), is considered as one of the most promising cathode materials for the next-generation lithium-ion batteries. In this work, a novel cell configuration with a top current collector was designed for Li2S based batteries. The nitrogen-doped carbon nanotube (N-CNT) film was applied on top of the cathode, which serves not only as a top current collector but also as a barrier layer to effectively impede the polysulfide diffusion and enhance the utilization of active materials. A sheet-like Li2S@C nanocomposite was synthesized from low-cost and environmentally friendly raw materials of lithium sulfate (Li2SO4) and activated graphite. The as-prepared Li2S@C composites were directly used as cathode materials without adding any binder or carbon additive, which enabled a high Li2S loading up to 68% in the total cathode weight. The cells exhibited superior electrochemical performance. The specific energy at 0.5C was 804 W h kg(-1) based on the total electrode weight including the N-CNT top current collector, which is among the highest values demonstrated so far for sulfur and Li2S cathodes

Terahertz filters based on frequency selective surfaces for high-speed terahertz switch

Localized plasmon modes are excited and probed in a large-area grating-gate GaN/AlGaN high-electron-mobility transistor structure embedded in a Fabry-Perot cavity using a terahertz time-domain spectroscopy (THz-TDS) at cryogenic temperature. Determined by the length of grating finger and the electron concentration, the frequency of localized plasmon modes can be continuously tuned by the gate voltage in the spectral range from 0.1 THz to 1.5 THz. When the plasmon frequency is tuned to be in resonance with the terahertz Fabry-Perot cavity mode, a strong coupling between the plasmon mode and the cavity mode is observed and the terahertz plasmon-polaritons are formed in such a cavity-coupled two-dimensional electron system. The electromagnetic simulations have confirmed the strong coupling between them

Probing of localized terahertz self-mixing in a GaN/AlGaN field-effect transistor

<div class="aip-paragraph">In our previous work [Sun <span class="etal">et al.</span>, Appl. Phys. Lett. <strong class="emphbold">100</strong>, 013506 (2012)], we inferred the existence of localized self-mixing in an antenna-coupled field-effect terahertz detector. In this Letter, we report a quasistatic self-mixing model taking into account the localized terahertz fields and its verification by comparing the simulated results with the experimental data in a two-dimensional space of the gate voltage and the drain/source bias. The model well describes the detector characteristics: not only the magnitude, but also the polarity, of the photocurrent can be tuned. The existence of strongly localized self-mixing in such detectors is confirmed.</div

The effect of symmetry on resonant and nonresonant photoresponses in a field-effect terahertz detector

The effect of the symmetries in the terahertz (THz) field distribution and the field-effect channel on THz photoresponse is examined. Resonant excitation of cavity plasmon modes and nonresonant self-mixing of THz waves are demonstrated in a GaN/AlGaN two-dimensional electron gas with symmetrically designed nanogates, antennas, and filters. We found that the self-mixing signal can be effectively suppressed by the symmetric design and the resonant response benefits from the residual asymmetry. The findings suggest that a single detector may provide both high sensitivity from the self-mixing mechanism and spectral resolution from the resonant response by optimizing the degree of geometrical and/or electronic symmetries. (C) 2015 AIP Publishing LLC