太赫兹量子级联激光器有源区有限元模拟

采用有限元分析法解决了太赫兹量子级联激光器(THz QCL)有源区模拟问题。由于InP基差频THz QCL有源区为千层纳米结构,无法拆分实验探索,因此模拟分析显得尤为必要。首先列出有源区量子结构的薛定谔方程,而后采用Galerkin有限元法改写薛定谔方程,再根据连续性和边界条件,得到本征值矩阵方程,最后采用Matlab写出运算程序求解本征值矩阵方程,求出波函数。针对不同有源区量子结构,设定材料、组分、厚度和周期数及外加偏压等参数,即可得到波函数模方、能级、频率和波长等模拟结果。选取InP基差频THz QCL结构进行验证,结果表明此模型切实可行,其拓展应用也可以解决GaAs THz QCL模拟问题。     

全息曝光形成连续工作的波长8.5微米分布反馈量子级联激光器

我们制作完成了波长8.5 µm附近的分布反馈量子级联激光器。使用全息曝光的方法完成了一级光栅的制备。通过在后腔面镀高反膜使器件能够完成从93K到210K连续工作并获得稳定的动态单模发射,边模抑制比20dB,调谐系数-0.277cm-1/K。80K时的输出功率超过100mW。     

内馈斩波串级调速系统的现场调试及运行时遇到的问题和解决方法

本文结合实际给出了内馈斩波串级调速系统现场调试的一些方法和注意事项，并针对实际运行时遇到的一些问题进行了分析，并给出了相应的解决方法。系统调试是一项细致而复杂的工作，也是系统运行前的一个重要步骤，应该引起工程技术人员的重视。     

InAs/GaAsSb带间级联中波红外焦平面研究

针对高工作温度红外探测器的迫切需求,设计并利用分子束外延技术制备了高晶格质量的2级带间级联中波红外探测材料,带间级联单元器件在最高323 K下可以测试到清晰的响应光谱,140 K下暗电流密度达到4×10~(-5)A/cm~(-2).并在此基础上利用干法刻蚀技术实现了320×256规模的台面型带间级联红外焦平面原型器件.焦平面测试结果表明其在80-120K范围内量子效率达到30%,127 K下噪声等效温差为55.1 mK,盲元率为2.3%.采用该焦平面器件在127 K下获得了较为清晰的演示性室温目标红外热成像.     

Confined Transformation of UiO‐66 Nanocrystals to Yttria‐Stabilized Zirconia with Hierarchical Pore Structures for Catalytic Applications

Solid acids as a substitution for hazardous liquid acids (e.g., HF and H₂SO₄) can promote many important reactions in the industry, such as carbon cracking, to proceed in a more sustainable way. Starting from a zirconium‐based metal‐organic framework (UiO‐66 nanocrystals), herein a transformative method is reported to prepare micro/mesoporous yttria‐stabilized zirconia (YSZ) encapsulated inside a mesoporous silica shell. It is then further demonstrated that the resultant reactor‐like catalysts can be used for a wide range of catalytic reactions. The acidity of the YSZ phase is found with rich accessible Lewis acid and Brønsted acid sites and they display superior performances for esterification (acetic acid and ethanol) and Friedel‐Crafts alkylation (benzylation of toluene). After being loaded with different noble metals, furthermore, hydrogenation of CO₂ and a one‐pot cascade reaction (nitrobenzene and benzaldehyde to N‐benzylaniline) are used as model reactions to prove the versatility and stability of catalysts. Based on the findings of this work, it is believed that this class of reactor‐like catalysts can meet future challenges in the development of new catalyst technology for greener heterogeneous catalysis.     

量子级联激光器的原理及研究进展

量子级联激光器的发明是半导体激光器领域里程碑的发展,开创了中远红外半导体激光的新领域,在红外对抗、毒品和爆炸物检测、环境污染监测、太赫兹成像等方向有广泛的应用前景.本文阐述了量子级联激光器的基本原理、以及材料和器件的研究,结合应用方向对其研究进展进行了综述性介绍.     

基于中红外量子级联激光器的SO2 和SO3 检测研究

二氧化硫 (SO2) 和三氧化硫 (SO3) 是工业废气排放中的重要物质, 对环境和人体健康危害很大, 但对于他们 在排放过程中的原位-在线测量一直是个挑战。采用可调谐二极管激光吸收光谱 (TDLAS) 技术, 基于 7.16 µm 量子级 联激光器 (QCL) 对 SO2 和 SO3 进行同时检测, 通过波长调制光谱技术提高测量系统的灵敏度和鲁棒性。在高温低压 条件下采用单光程-小体积的气体吸收池利用 TDLAS 同时测量 SO2 和 SO3 的吸收谱线, 测量的 SO2 和 SO3 的吸收 光谱充分分离, 从而确保了测量的准确性。同时, 修正了温度变化对 SO2 气体浓度测量的影响, 并提出了用已知浓度 的 SO2 来定标未知浓度的 SO3 气体。 Allan 方差分析表明, 在 34 s 的积分时间内, SO2 的最小检测限达到了1.98×10−6 cm3·cm−3, SO3 可探测的最低浓度为 1.575 ×10−6 cm3·cm−3。系统的上升响应时间约为 16 s, 下降响应时间约为 18 s。     

一种基于改进Adaboost的人体检测算法

本文采用改进的Adaboost算法对静态图像中人体进行检测。针对传统算法中训练速度较慢,并且存在风险敏感的问题。本文提出一种快速特征选择算法,通过构造统计表,保存特征信息,避免每轮弱分类器训练时对所有特征重新计算分类误差;并结合fisher判别分析对选出的弱分类器进行训练,学习得到一个新的线性判别方程,最大化不同类别数据之间的可分离性,达到优化强分类器降低风险敏感影响的目的。实验结果表明,相对于传统的Adaboost算法,本文给出的方法加快了特征选择的速度,并具有较好的检测性能。     

Interband Cascade Lasers with Wavelengths Spanning 2.9 μm to 5.2 μm

We report an experimental investigation of four interband cascade lasers with wavelengths spanning the mid-infrared spectral range, i.e., 2.9 μm to 5.2 μm, near room temperature in pulsed mode. One broad-area device had a pulsed threshold current density of only 3.8 A/cm² at 78 K (λ = 3.6 μm) and 590  A/cm² at 300 K (λ = 4.1 μm). The room-temperature threshold for the shortest-wavelength device (λ = 2.6 μm to 2.9 μm) was even lower, 450 A/cm². A␣cavity-length study of the lasers emitting at 3.6 μm to 4.1 μm yielded an internal loss varying from 7.8 cm⁻¹ at 78 K to 24 cm⁻¹ at 300 K, accompanied by a decrease of the internal efficiency from 77% to 45%.     

Synergy of Pickering Emulsion and Sol‐Gel Process for the Construction of an Efficient,Recyclable Enzyme Cascade System

An efficient, easily recyclable enzyme cascade system based on nanoparticle‐stabilized capsules (NPSCs) is constructed through a synergy of a Pickering emulsion and sol‐gel process. Specifically, oligodopa‐coated titania nanoparticles (biomimetic titania) containing the first enzyme (FateDH) are synthesized through a bioadhesion‐assisted biomimetic mineralization approach. The biomimetic titania is then spontaneously assembled at the interface between the oil phase (hexadecane/butyl titanate (BuTi) mixture) and water phase during the formation of Pickering emulsions. The sol‐gel process of BuTi can produce not only butanol for assisting the formation of Pickering emulsions but also titania gel particles (sol‐gel titania) for cross‐linking the biomimetic titania through catechol‐titanium chelating. The NPSCs obtained, which contain the first enzyme, conjugate the second enzyme (FaldDH) onto the surface for constructing the enzyme cascade system. The system exhibits high activity and stability, particularly, superior recyclability for conversion of CO₂ into formaldehyde. In detail, the system shows a formaldehyde yield of 50.0%, and can quickly float onto the air/water interface soon after stopping the agitation of reaction mixtures, which ensures that the formaldehyde yield keeps almost unaltered after 10 times recycling. This study will be useful for facile construction of a wealth of catalytic systems with efficient, recyclable attributes.