Performance improvements of ultraviolet/infrared dual-band detectors

Results are reported on dual-band detectors based on a GaN/AlGaN structure operating in both the ultraviolet–midinfrared (UV–MIR) and ultraviolet–farinfrared (UV–FIR) regions. The UV detection is due to an interband process, while the MIR/FIR detection is from free carrier absorption in the emitter/contact followed by internal photoemission over the barrier at the GaN/AlGaN interface. The UV detection, which was observed from 300 K to 4.2 K, has a threshold of 360 nm with a peak responsivity of 0.6 mA/W at 300 K. The detector shows a free carrier IR response in the 3–7 μm range up to 120 K, and an impurity response around 54 μm up to 30 K. A response in the range 7–13 μm, which is tentatively assigned to transitions from C impurities and N vacancies in the barrier region, was also observed. It should also be possible to develop a detector operating in the UV–visible–IR regions by choosing the appropriate material system. A dual-band detector design, which allows not only to measure the two components of the photocurrent generated by UV and IR radiation simultaneously but also to optimize the UV and IR responses independently, is proposed.     

MBE-grown MCT hetero- and nanostructures for IR and THz detectors

We present an overview of our technological achievements in the implementation of detector structures based on mercury cadmium telluride (MCT) heterostructures and nanostructures for IR and THz spectral ranges. We use a special MBE design set for the epitaxial layer growth on (013) GaAs substrates with ZnTe and CdTe buffer layers up to 3” in diameter with the precise ellipsometric monitoring in situ. The growth of MCT alloy heterostructures with the optimal composition distribution throughout the thickness allows for the realization of different types of many-layered heterostructures and quantum wells to prepare the material for fabricating single- or dual-band IR and THz detectors.We also present the two-color broad-band bolometric detectors based on the epitaxial MCT layers that are sensitive in 150–300-GHz subterahertz and infrared ranges from 3 to 10 μm, which operate at the ambient or liquid nitrogen temperatures as photoconductors, as well as the detectors based on planar HgTe quantum wells. The design and dimensions of THz detector antennas are optimized for reasonable detector sensitivity values. A special diffraction limited optical system for the detector testing was designed and manufactured. We represent here the THz images of objects hidden behind a plasterboard or foam plastic packaging, obtained at the radiation frequencies of 70, 140, and 275 GHz, respectively.     

空间目标红外双波段比色测温法精度分析

针对空间目标与地基望远镜红外成像传感器终端之间的不确知参量将降低双波段比色测温法求解精度,且精度影响程度未知,假设目标为灰体,对包含不确知参量的最大似然估计函数关于发射率求偏导,建立基于红外探测器测量电子数的双波段比色测温数学模型,并进行双波段比色测温法的蒙特卡洛仿真实验与精度分析。对于大气透过率的估算,提出应用红外自然星体的大气透过率现场标校方法。空间目标温度反演精度与成像探测器的信噪比、大气透过率、地球热辐射以及波段之间的发射率差异等未知参量的估算精度有关。结果表明:信噪比高于20,波段之间发射率差异小于0.03,地球热辐射预测精度优于50%,大气透过率预测精度优于10%时,比色测温法优于40 K的温度估计精度。     

基于特征点自动匹配的红外图像配准研究

在模糊和含噪声的红外图像配准中,利用角点检测实现特征点的选择,在提高角点提取效率的同时又保证了角点提取的精度。根据互相关的双向匹配实现对应特征点的自动匹配,然后由对应的特征点对估计出仿射变换的参数。实测的数据和计算结果表明,这种方法对于双波段红外图像的配准是有效的,而且有利于后续的图像融合。     

紫外至近红外积分球辐射定标系统

本文描述一种定标系统,它采用直径250cm的积分球辐射源作定标源,其辐射孔径大(直径40cm)、辐射功率高、具有较好的空间均匀性、广角度的漫射性、输出稳定以及宽波段的定标范围(0.25～2.5μm).本系统可用于光学遥感传感器和有关光辐射测量仪器的定标.     

机载红外热像仪探测海面温度场的仿真计算

通过建立海洋背景下的红外辐射模型,对机栽红外探测系统所获得的热图进行了仿真计算,提出了一种从探测器红外焦平面上的探测像元到海面红外辐射单元的映射方法。利用MODTRAN软件计算了被探测海域各红外辐射单元通过大气传输后最终到达机载红外热像仪探测像元的红外辐射强度,最后利用Visual ＋＋结合计算机图形学方法实现了红外热图的仿真计算。仿真结果基本反映了海面温度场的红外特性。     

Spectral signs of photochemical reactions when blood is exposed <Emphasis Type="Italic">in vivo</Emphasis> to therapeutic doses of ultraviolet radiation

We have used the absorption spectra of whole blood, erythrocytes, and plasma to study photochemical reactions initiated by exposure of blood in vivo to UV radiation (UV irradiation) in the UV-visible and IR regions of the spectrum. We have established that when blood is exposed to therapeutic doses of UV radiation (0.5 J/cm²), the absorption of blood proteins decreases as monitored using the UV absorption and luminescence bands of the proteins; photochemical reactions are initiated in the protein and heme components of the hemoglobin. For the studied doses, the reversible reaction of photodissociation of hemoglobin complexes with oxygen is one of the most likely primary reactions initiated by UV irradiation of blood. We conclude that changes in the position and relative intensities of the IR absorption bands of the peptide groups (stretching and bending vibrations of NH, CN, and CO bonds) may be due to conformational transitions in the blood protein macromolecules, induced with a change in the intermolecular hydrogen bonds on absorption of the UV radiation by the blood. The changes in the absorption spectra of blood initiated by UV irradiation are compared with the results of laboratory blood analyses. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 400–405, May–June, 2008.     

Fast-speed self-powered PEDOT: PSS/α-Ga2O3 nanorod array/FTO photodetector with solar-blind UV/visible dual-band photodetection

The $\alpha $-Ga$_{2}$O$_{3}$ nanorod array is grown on FTO by hydrothermal and annealing processes. And a self-powered PEDOT:PSS/$\alpha $-Ga$_{2}$O$_{3}$ nanorod array/FTO (PGF) photodetector has been demonstrated by spin coating PEDOT:PSS on the $\alpha $-Ga$_{2}$O$_{3}$ nanorod array. Successfully, the PGF photodetector shows solar-blind UV/visible dual-band photodetection. Our device possesses comparable solar-blind UV responsivity (0.18 mA/W at 235 nm) and much faster response speed (0.102 s) than most of the reported self-powered $\alpha $-Ga$_{2}$O$_{3}$ nanorod array solar-blind UV photodetectors. And it presents the featured and distinguished visible band photoresponse with a response speed of 0.136 s at 540 nm. The response time is also much faster than the other non-self-powered $\beta $-Ga$_{2}$O$_{3 }$ DUV/visible dual-band photodetectors due to the fast-speed separation of photogenerated carries by the built-in electric field in the depletion regions of PEDOT:PSS/$\alpha $-Ga$_{2}$O$_{3}$ heterojunction. The results herein may prove a promising way to realize fast-speed self-powered $\alpha $-Ga$_{2}$O$_{3}$ photodetectors with solar-blind UV/visible dual-band photodetection by simple processes for the applications of multiple-target tracking, imaging, machine vision and communication.     

红外小目标与背景辐射对比度的研究

红外目标与背景的对比度特征是红外探测系统检测的重要特征。研究了目标和背景在探测器上的辐射照度,提出了一种红外小目标与背景的辐射对比度,分析了该目标与背景对比度的相关因素。     

Self-sum- and -difference-frequency mixing in GdAl(3)(BO(3))(4):Nd(3+) for generation of tunable ultraviolet and infrared radiation

We exploited Nd(3+) laser emission at 1061.9 nm ((4)F(3/2)?(4)I(11/2) channel) in a self-chi((2)) active GdAl(3)(BO(3))(4):Nd(3+) laser crystal. UV radiation was obtained from a 1.8% yield from self-sum-frequency mixing: 1/pump + 1/1061.9 = 1/UV, during pumping in the Nd(3+) (4)G(5/2)-(2)G(7/2) levels near 588 nm. The UV tunability had a range of 378-382 nm. We have demonstrated, for the first time to our knowledge, generation of coherent IR radiation from a self-difference-frequency mixing laser: 1/pump - 1/1061.9 = 1/IR. We got a 0.5% yield and tunability in the 1305-1365-nm range.     

一种近红外探测器的光谱响应率测量

对近红外辐射功率光谱绝对响应率的定标技术进行了研究。设计了一种制冷扩展波长型的InGaAs探测器，为了使其能够作为功率传递的标准探测器工作在（1.2～2.5）μm波长范围，对探测器的光谱响应率进行了测量。首先在1260nm波长下进行绝对功率传递的标定试验，然后用基于红外单色仪的光谱比较系统（SCF）测量了探测器的相对光谱响应率。结合2个步骤的数据，最终可以得到探测器的绝对光谱响应率。     

Time-resolved multispectral luminescence method for analysis of minerals

We have developed a procedure for time-resolved luminescence analysis with excitation of samples by a nanosecond electron beam and recording the luminescence decay kinetics in four spectral bands. Using as an example analysis of different types of the mineral charoite, we have shown that the time variation of the ratio of radiation fluxes in selected spectral ranges spanning the UV, visible, and IR regions can be used for analytical purposes to identify or differentiate materials, and is an additional source of information about the sample.     

Dual-band pixelless upconversion imaging devices

We have proposed a type of mid-infrared (MIR) and far-infrared (FIR) dual-band imaging device, which employs the photon frequency upconversion concept in a GaN/AlGaN MIR and FIR dual-band detector integrated with a GaN/AlGaN violet light emitting diode. On the basis of the photoresponse of single-period GaN/AlGaN dual-band detectors, we present the detailed optimization of multiperiod GaN emitter/AlGaN barrier detectors and their applications to dual-band pixelless upconversion imaging. Satisfying images have been received through the analysis of the modulation transfer function and the upconversion efficiency in the GaN/AlGaN dual-band pixelless upconverters, which exhibit good image resolution, high quantum efficiency, and negligible cross talk.     

IR synchrotron diagnostics. Part 1: Wide-band long-focus optics

An optical channel for extracting, transporting, and applying (to a detector) IR synchrotron radiation covering a wide wavelength range is developed. The design and study of optical systems with long-focus entrance objective and mirror lenses, as well as with a field condenser lens, are reported. Practical use of IR optics combined with integrated and position-sensitive detectors in accelerator experiments with synchrotron radiation is described.     

红外紫外双色光谱的产生

本文给出了在红外光谱多外利用热受激后的原子材料产生紫外光谱的方法。文中给出了计算数据和实验结果。     

双微波源共轴辐射馈线结构的设计

设计了一种将两个不同波段微波源输出微波馈向同一个馈源喇叭的双波段馈线结构。该结构不仅对两个微波源输出的TM01模进行了有效的模式转换,而且实现了两个波段的微波共用辐射天线。采用双弯曲圆波导模式转换器实现高频段微波源输出微波的模式转换和轴线的定量平移;采用中间模式为矩形波导TE10模的圆波导TM01模-同轴波导TE11模的模式转换器,实现低频段微波源输出微波的模式转换及与高频段微波源输出微波的共轴输出。数值仿真结果验证了设计思路的正确性。     

海空背景下红外-紫外双色探测技术研究

舰船采用紫外-红外多传感器探测低空飞行的导弹、飞机等目标，对各个传感器采集的目标图像数据进行融合处理，可提高对目标的探测识别概率。本文分析了红外传感器器和紫外传感器的各自的优越性、海空背景下导弹羽烟的紫外辐射传输特性，得出采用红外-紫外图像融合技术能使红外、紫外传感器的优势得到互补，融合级别适合在特征级上进行，并对红外-紫外双色探测技术进行了展望。     

基于氧化物的0.8~1.7μm和3.7~4.8μm硬质宽带红外增透膜研制

从实际应用出发,在0°入射的条件下,在ZnS基底上针对0.8~1.7 μm和3.7~4.8 μm两个红外波段,设计并制备了双波段红外增透膜。论述了材料选择、膜系设计和制备方法,最终使用等离子辅助沉积技术在ZnS窗口上制备出双波段红外增透膜,透过率及环境测试结果表明：在0.8~1.7 μm波段双面平均透过率大于95%,在3.7~4.8 μm波段双面平均透过率大于96%。膜层结合牢固并有良好的耐摩擦性能。     

紫外探测器的辐射定标及标准传递

针对定量化遥感的深入研究和探测器测量精度的提高,本文对紫外波段探测器的标定方法和标准的传递进行了研究。介绍了紫外探测器低温辐射计的工作原理、标准建立过程及发展现状,探讨了美国国家标准研究院（NIST）传递标准探测器的选取和标准传递过程。文中的研究为探测器定标方法的研究提供了理论基础,对提高标准探测器定标精度,促进其工程化应用具有借鉴意义。     

Surface plasmon-enhanced dual-band infrared absorber for VO_x-based microbolometer application

We propose a periodic structure as an extra absorption layer(i.e., absorber) based on surface plasmon resonance effects, enhancing dual-band absorption in both middle wavelength infrared(MWIR) and long wavelength infrared(LWIR)regions. Periodic gold disks are selectively patterned onto the top layer of suspended SiN/VO_2/SiN sandwich-structure.We employ the finite element method to model this structure in COMSOL Multiphysics including a proposed method of modulating the absorption peak. Simulation results show that the absorber has two absorption peaks at wavelengths λ =4.8 μm and λ = 9 μm with the absorption magnitudes more than 0.98 and 0.94 in MWIR and LWIR regions, respectively. In addition, the absorber achieves broad spectrum absorption in LWIR region, in the meanwhile, tunable dual-band absorption peaks can be achieved by variable heights of cavity as well as diameters and periodicity of disk. Thus, this designed absorber can be a good candidate for enhancing the performance of dual band uncooled infrared detector, furthermore, the manufacturing process of cavity can be easily simplified so that the reliability of such devices can be improved.