The determination of the x value in doped Hg_(1-x)Cd_x Te by transmission spectra

Variable-temperature transmission/absorption spectra are measured on As-doped Hgl-xCdxTe grown by molec- ular beam epitaxy. The nonlinear temperature-dependent shift of the absorption edge is also observed, which is similar to our previous report on VHg （unintentionally）-doped HgCdTe. By referring to the empirical formulas of Eg（x,T）, the x value of the epilayer is calculated and its inconsistency between the extreme temperatures （e.g. 10 and 300 K） is discussed. The results confirm the assumption of the effect of shallow levels on the shift of the absorption edge, and suggest that the x value （or Eg） in intrinsic/extrinsic-doped HgCdTe should be determined by referring to as low a temperature as possible （e.g. 10 K）, and not the commonly used temperatures of 77 or 300 K, when the transmission spectrum should be employed. This can give brief guidelines for fabricating HgCdTe-related devices.

Germanium-tin alloys： applications for optoelectronics in mid-infrared spectra

We summarize our work of the optoelectronic devices based on Germanium-tin （GeSn） alloys assisted with the Si3N4liner stressor in mid-infrared （MIR） domains. The device characteristics are thoroughly analyzed by the strain distribution,band structure, and absorption characteristics. Numerical and analytical methods show that with optimal structural pa-rameters, the device performance can be further improved and the wavelength application range can be extended to 2~5 μm in the mid-infrared spectra. It is demonstrated that this proposed strategy provides an effective technique for the strained-GeSn devices in future optical designs, which will be competitive for the optoelectronics applications in mid-infrared wavelength.

Spectral reconstruction of the flash X-ray generated by Dragon-I LIA based on transmission measurements

The Dragon-I linear induction accelerator(LIA)at China Academy of Engineering Physics generates 20 Me V flash X-rays mainly for radiography applications in fluid dynamics.Its spectral information is quite important for diagnostic X-ray imaging applications,but because of its short pulse and great radiation intensity,direct measurement is impossible.In this work,we propose a new method based on transmission measurements to obtain the flash X-ray spectrum.Pure iron cylinders were used as attenuation material,and alanine dosimeters were attached on their rear bottom to record the dose after different degrees of attenuation.Iterative least square method was used to unfold the spectrum,while Geant4 Monte Carlo code was used to simulate the X-ray spectrum.The unfolded spectrum and the simulated spectrum have a high degree of consistency,with the reduced chi-square value of 0.044.This shows that the method is reliable in estimating megavoltage highintensity X-ray spectrum.

Design of Time-Resolved Shifted Dual Transmission Grating Spectrometer for the X-Ray Spectrum Diagnostics

A new time-resolved shifted dual transmission grating spectrometer （SDTGS） is designed and fabricated in this work. This SDTGS uses a new shifted dual transmission grating （SDTG） as its dispersive component, which has two sub transmission gratings with different line densities, of 2000 lines/mm and 5000 lines/mm. The axes of the two sub transmission gratings in SDTG are horizontally and vertically shifted a certain distance to measure a broad range of 0.1-5 keV time-resolved X-ray spectra. The SDTG has been calibrated with a soft X-ray beam of the synchrotron radiation facility and its diffraction efficiency is also measured. The designed SDTGS can take full use of the space on a record panel and improve the precision for measuring spatial and temporal spectrum simultaneously. It will be a promising application for accurate diagnosis of the soft X-ray spectrum in inertial confinement fusion.

Disorder Effect on the Transmission of Second Harmonic Waves in One-Dimensional Periodically Poled LiTaO₃

One of the methods for calculating electromagnetic wave dispersion in multi-layer structures is the transfer matrix method. In this paper, we use the transfer matrix method for second harmonic generation in a nonlinear multilayer structure. The nonlinear photonic crystals investigated in this paper are as one-dimensional multi-layered structures including ferroelectric materials such as LiTaO3. Our goal is to investigate the effect of the disorder on the transmission spectrum of electromagnetic waves. Our results showed that positional disorder has different effects on the transmitting band and the gap band. The disorder in the transmitting band reduces the transmission coefficient of the waves and increases the transmission coefficient of the waves in the gap band. Such work has not yet been done on nonlinear photonic crystals producing the second harmonic.

Chinese Spirits Identification Model Based on Mid-Infrared Spectrum

Applying computer technology to the field of food safety,and how to identify liquor quickly and accurately,is of vital importance and has become a research focus.In this paper,sparse principal component analysis(SPCA)was applied to seek sparse factors of the mid-infrared(MIR)spectra of five famous vintage year Chinese spirits.The results showed while meeting the maximum explained variance,23 sparse principal components(PCs)were selected as features in a support vector machine(SVM)model,which obtained a 97%classification accuracy.By comparison principal component analysis(PCA)selected 10 PCs as features but only achieved an 83%classification accuracy.Although both approaches were better than a direct SVM approach based on the classification results(64%classification accuracy),they also demonstrated the importance of extracting sparse PCs,which captured most important information.The combination of computer technology SPCA and MIR provides a new and convenient method for liquor identification in food safety.

Predicting nitrogen use efficiency,nitrogen loss and dry matter intake of individual dairy cows in late lactation by including mid‑infrared spectra of milk samples

Background Nitrate leaching to groundwater and surface water and ammonia volatilization from dairy farms have negative impacts on the environment.Meanwhile,the increasing demand for dairy products will result in more pollution if N losses are not controlled.Therefore,a more efficient,and environmentally friendly production system is needed,in which nitrogen use efficiency(NUE)of dairy cows plays a key role.To genetically improve NUE,extensively recorded and cost-effective proxies are essential,which can be obtained by including mid-infrared(MIR)spectra of milk in prediction models for NUE.This study aimed to develop and validate the best prediction model of NUE,nitrogen loss(NL)and dry matter intake(DMI)for individual dairy cows in China.Results A total of 86 lactating Chinese Holstein cows were used in this study.After data editing,704 records were obtained for calibration and validation.Six prediction models with three different machine learning algorithms and three kinds of pre-processed MIR spectra were developed for each trait.Results showed that the coefficient of determination(R2)of the best model in within-herd validation was 0.66 for NUE,0.58 for NL and 0.63 for DMI.For external validation,reasonable prediction results were only observed for NUE,with R2 ranging from 0.58 to 0.63,while the R2 of the other two traits was below 0.50.The infrared waves from 973.54 to 988.46 cm−1 and daily milk yield were the most important variables for prediction.Conclusion The results showed that individual NUE can be predicted with a moderate accuracy in both within-herd and external validations.The model of NUE could be used for the datasets that are similar to the calibration dataset.The prediction models for NL and 3-day moving average of DMI(DMI_a)generated lower accuracies in within-herd validation.Results also indicated that information of MIR spectra variables increased the predictive ability of models.Additionally,pre-processed MIR spectra do not result in higher accuracy than original MIR spectra in the external validation.These models will be applied to large-scale data to further investigate the genetic architecture of N efficiency and further reduce the adverse impacts on the environment after more data is collected.

GaN衬底上ZnS纳米薄膜的结构、光学和电学特性

采用脉冲激光沉积技术在GaN衬底上制备了ZnS纳米薄膜。通过XRD和SEM对薄膜结晶情况和截面结构进行了表征,并测量了ZnS纳米薄膜的透射光谱和ZnS/GaN异质结的Ⅰ-Ⅴ特性曲线。ZnS纳米薄膜在可见光区的透过率较高,平均透过率在80%以上,经过退火处理,透过率增大。Ⅰ-Ⅴ特性曲线表明,ZnS/GaN形成了异质结,具有和普通二极管相似的整流特性。在正向偏压下电流随着电压的增加而增大。退火处理后异质结的导通电压减小。这些特性表明,ZnS纳米薄膜在无人机载传感器和航空电子系统中的光电二极管、光电探测器、光伏电池等领域有着潜在的应用价值。

All Fiber-optic Fluorescent Spectral Measurement and Analysis on Alga Chla/c Characteristics

The fluorescent principle used for measuring alga characteristic parameters and the optimum structure design of the instrument are discussed. The fluorescent spectrum of Chla/c and the time-resolved different spectrum ΔA(λ,t) are given. The research provides an effective method for considering the density and the classification of algae, which will be helpful to monitor sea pollution.

Autonomous and Mobile Prototype of Curvature Sensor with Remote Reliable Communication of Spectral Curvature

Through the creation and construction of a curvature sensor of accelerometer type, using the spectral curvature concept or curvature energy that measures curvature in Volts/m3, an autonomous and mobile censorship of curvature sensing with reliable data transmission/reception in real time and remote position is designed and constructed considering the spectra of curvature of the measured curvature energy during the advance of the prototype as the normed measure by with β , a constant rationalized parameter according with the required advance of the mobile device in the control scale of their velocity. Likewise, the sensed curvature data are digitalized through wireless interconnectivity using a HC-05 Module with a programmable device that includes logic blocks whose interconnection and functionality can be configured according to the sensor measure in situs. Also an application is planted to the obtaining of an energy plus due to the curvature that could be used in the displacement of a vehicle.

A study on resonance Rayleigh scattering spectra of Humic Acid (HA)

This paper deals with the influences of pH, acidity and ionic intensity of the solutions on the resonance Rayleigh scattering spectra and fluorescence spectra of humic acid. When the pH value is low and the acidity and ionic intensity are high, the resonance Rayleigh spectra and fluorescence spectra both show a tendency of increasing, though the former's intensity is much higher. In combination with the transmission electron microscope data, the factors leading to the occurrence and enhancement of the resonance Rayleigh scattering spectra of humic acid were explored. It is considered that particle enlargement caused by aggregation, the increase of heterogeneity, the increase of hydrophobility, the formation of interface, etc., are the factors leading to the occurrence and enhancement of the resonance Rayleigh scattering spectra of humic acid. As the intensity of the resonance Rayleigh scattering spectra of humic acid is much higher, resonance Rayleigh scattering spectroscopy can be used as a newly developed spectrum technology, which is more sensitive and simpler, to study humic acid and its complicated behaviors.

Bandpass transmission spectra of a whisperinggallery microcavity coupled to an ultrathin fiber

Tapered fibers with diameters ranging from 1 to 4 μm are widely used to excite the whispering-gallery(WG)modes of microcavities. Typically, the transmission spectrum of a WG cavity coupled to a waveguide around a resonance assumes a Lorentzian dip morphology due to resonant absorption of the light within the cavity. In this paper, we demonstrate that the transmission spectra of a WG cavity coupled with an ultrathin fiber(500–700 nm)may exhibit both Lorentzian dips and peaks, depending on the gap between the fiber and the microcavity. By considering the large scattering loss of off-resonant light from the fiber within the coupling region, this phenomenon can be attributed to partially resonant light bypassing the lossy scattering region via WG modes, allowing it to be coupled both to and from the cavity, then manifesting as Lorentzian peaks within the transmission spectra.This implies the system could be implemented within a bandpass filter framework.

Infrared-transmission spectra and hydrogen content of hydrogenated amorphous silicon

In this paper, two kinds of methods of calculating the hydrogen content of a-Si:H thin film by means of the wagging mode and the stretching modes of infrared-transmission spectra , are investigated. The reason for the difference in these two calculation results is analyzed. If the contents of SiH2 and (SiH2)n are indicated in terms of a structure factor F=(I840+I880)/I2000, it is shown that the calculation results obtained from the two different methods are almost equal when the refractive index n is approximately 3.4 or the fitting thickness is between 0.71 and 0.89 mm in the case of a small F. It is shown that the ways of fabrication of thin film can influence silicon-hydrogen bonding configuration of a-Si:H film, and different ways of fabrication can lead to different contents of SiH2 and (SiH2)n. The uniformity of the thin film with a big F is bad. In this case, there is great difference between the thickness measured by the SurfCom408A surface profile apparatus and the thickness obtained by fitting the fringes; and the hydrogen contents of a-Si:H films obtained by means of the wagging mode and the stretching modes are different, too. But the fabrication of the MWECR CVD assisted by CAT CVD can effectively restrain the formation of SiH2 and (SiH2)n.

近红外透射和紫外吸光度法检测水质化学需氧量的研究

化学需氧量(COD)是表征水体中有机物污染程度的一个综合性指标。基于光电检测技术发展起来的红外透射法和紫外吸光度法相较于传统湿化学法有着精度高,速度快,非接触,无二次污染等优点。以邻苯二甲酸氢钾配置的标准液为实验对象,分别采用近红外透射法和紫外吸光法采集标准液的近红外光谱和紫光吸光度光谱,对光谱进行不同的预处理后运用偏最小二乘法建立红外透射光谱和紫外吸光光谱下的COD定量分析模型。对实验结果进行数据分析后结果显示两种方法均可用于测量COD,紫外吸光法比红外透射法有更高的相关度,但是预测精度却不如后者。

红外透射光谱在HgCdTe外延薄膜性能评价中的应用

用最新发表的ＨｇＣｄＴｅ材料的光学常数对ＭＢＥ工艺生长的ＨｇＣｄＴｅ／ＣｄＴｅ／ＧａＡｓ材料的透射光谱进行了理论计算．对受生长工艺破坏的衬底背面再次进行抛光处理，消除因表面不平整引起的漫反射效应，使实验测量得到的光谱曲线与理论计算结果很好地吻合，由此得到的ＨｇＣｄＴｅ和ＣｄＴｅ外延层的厚度和解理面上用显微镜测量的数值相同，准确度优于±０．２μｍ．确定ＨｇＣｄＴｅ组分的准确度优于±０．

Ge_(28)Sb_6S_((66-x))Se_x玻璃系统光学特性与结构

采用熔融-急冷法制备了系列Ge28Sb6S(66-x)Sex(x=0,10,20,30摩尔比)硫系玻璃样品.分别测试了样品的密度、折射率、可见-近红外透过光谱、红外透过光谱以及喇曼光谱,并分析了在Ge-Sb-S中引入Se对其物理、光学特性的影响.利用喇曼光谱讨论了玻璃的结构与特性之间的关系.结果表明:随着Se含量的增加,样品的密度和线性折射率都增大,可见和红外截止波长都发生红移,纯硫化物玻璃样品主要由GeS4四面体和SbS3三角锥组成,随着Se逐渐代替S,硫-硒混合样品中逐渐出现了GeS4-xSex结构单元以及链状和环状的Se-Se键.

HF/DF激光传输的大气衰减特性

大气中的水汽对DF激光主要强线的吸收相对较小,而HF激光的大多数谱线受水汽和CO2分子等的吸收较大。利用较新的HITRAN96数据库和我国不同地区的气象资料,采用逐线积分法计算了HF/DF激光的大气衰减情况。所选的谱线中,在合肥地区(年平均),HF的水汽吸收系数最大值可达到10km-1的数量级,二氧化碳吸收系数最大可达10-4～10-3km-1量级,P2(8)线吸收最弱;DF激光水汽吸收系数最大值可达到10-1km-1,比HF低2个量级,且随高度衰减很快,10km处就到10-5～10-4km-1量级,P2(8)线吸收最弱。在我国,由南向北,由夏季到冬季,水汽浓度减少,大气对HF/DF激光的吸收率也相应地递减。

MOVPE生长的InGaN/GaN单量子阱的光致发光和光吸收特性(英文)

研究了用金属有机物气相外延(MOVPE)法在蓝宝石衬底上生长的In组分浓度保持不变的InGaN/GaN单量子阱结构在室温下的发光特性和光吸收特性。实验结果表明,在InGaN厚度<3 nm时,随着样品InGaN势阱层宽度的增加(1 nm),光致发光(PL)谱的发光峰值波长出现明显的红移33 nm现象,而且发光强度下降8%,谱线半峰全宽(FWHM)展宽,通过对样品的透射、反射光谱研究发现,量子阱层窄(1.5 nm)的样品在波长接近红外区时出现无吸收的现象,即R+T达到了100%,而在阱层较宽的样品中没有发现这一现象,对引起这些现象的原因进行了讨论。这些结果有助于开发和优化三族氮化物半导体光电器件的进一步研究工作。

纯LaAlO_3和Ce^(3+)∶LaAlO_3单晶的吸收谱和透过谱研究

本文采用中频感应提拉法成功生长了LaAlO3 和Ce3 + ∶LaAlO3 晶体。沿生长方向即a轴方向切割、抛光后得到实验样品。测试了氢气退火前后纯LaAlO3 和Ce3 + ∶LaAlO3 从 190nm到 2 5 0 0nm的吸收谱和透过谱。测试结果表明 :纯LaAlO3 晶体在 196～ 2 2 0nm处出现宽带吸收 ,氢气退火后此一波段的吸收系数明显降低 ;未退火的Ce∶LaAlO3晶体在 196～ 2 0 9nm ,2 4 6nm ,314nm出现明显的吸收波段 ,氢气退火后其吸收谱发生显著变化 ,在 198,2 0 6 ,2 14 ,2 4 6和 314nm处出现对应于Ce3 + 的 4f- 5d的跃迁吸收 ;Ce∶LaAlO3 晶体较之纯LaAlO3 晶体在红外区的透过率要高 ;氢气退火后 ,Ce∶LaAlO3 晶体和纯LaAlO3