含有AlGaAs插入层的InAs/GaAs三色量子点红外探测器

本文报道了采用分子束外延技术制备的三色InAs/GaAs量子点红外探测器. 器件采用nin型结构, 吸收区结构是在InGaAs量子阱中生长含有AlGaAs插入层的InAs量子点, 器件在77 K下的红外光电流谱有三个峰值: 6.3, 10.2和11 μm. 文中分析了它们的跃迁机制, 并且分别进行了指认. 因为有源区采用了不对称结构, 所以器件在外加偏压正负方向不同时, 光电流谱峰值的强度存在一些差异. 不论在正偏压或者负偏压下, 当偏压达到较高值, 再进一步增大偏压时, 都出现了对应于连续态的跃迁峰强度明显下降的现象, 这是由量子点基态与阱外连续态的波函数交叠随着偏压进一步增大而迅速减小导致的.     

New band system of YbI molecule

Thermal emission spectrum of YbI molecule has been photographed for the first time in the spectral regionλλ 6100–6400 Å using Saha’s high temperature furnace at a reciprocal linear dispersion of 7.3 Å/mm. A total of 52 single-headed and violet degraded bands have been recorded and are classified into a single system. Vibrational analysis has been carried out and it has been suggested that system arises from the ground state with the vibrational constantω″ _e=153.0 cm^?1.     

Optical Recording Performance of Azo Nickel Chelate Thin Film

1IntroduCtionAndyeshavebeenwidelystudiedasmaterialsforreverwhleoPticalstorae,forholographasanexamPle,inwhichisomerizatiOnofazomoeculesekistSbetWeentransandcisform['~'].HOWever,therearetwomainproblemswhichhavelindtedtheirfurtherpracticalaPplications.oneisthatthesbetransformationspeedbetweenisomers,vawingfroInseveralhacrosecondstoseveralseconds,can'tmeetthehighspeeddemandofdatastorage.Theotheristhattheunstablecisstateofazodyesthermallyre-isomerizestothemorestabletransisomerverycommnly.Aithou…     

Optical Recording Performance of Azo Nickel Chelate Thin Film

The absorption,transmission and reflection spectra of spin-coated films of Ni(azo)2 (azo nickel chelate) were measured. Because of the intermolecular aggregation,the absorption peak of Ni(azo)2 thin film has a red-shift of about 40 nm with respect to that of it in methanol solution. The fabricated optical disk showed a reflectivity of 48% and its carrier-noise ratio (CNR) was greater than 45 dB when recording with 7.5 mW laser power at the wavelength of 780 nm.     

Effect of the nonlinearity of the CCD in Fourier transform profilometry on spectrum overlapping and measurement accuracy

In Fourier transform profilometry (FTP), we must restrain spectrum overlapping caused by the nonlinearity of the charge coupled device (CCD) and increase the measurement accuracy of the object shape. Firstly, the causes of producing higher-order spectrum components and inducing spectrum overlapping are analysed theoretically, and a simple physical explanation and analytical deduction are given. Secondly, aiming to suppress spectrum overlapping and improve measurement accuracy, the influence of spatial carrier frequency of projection grating on them is analysed. A method of increasing the spatial carrier frequency of projection grating to restrain or reduce the spectrum overlapping significantly is proposed. We then analyze the mechanism of how the spectrum overlapping is reduced. Finally, the simulation results and experimental measurements verify the correction of the proposed theory and method.     

Effect of the nonlinearity of CCD in Fourier transform profilometry on spectrum overlapping and measurement accuracy

In Fourier transform profilometry (FTP), we must restrain spectrum overlapping caused by the nonlinearity of charge coupled device (CCD) and increase the measurement accuracy of object shape. Firstly, the causes of producing higher-order spectrum components and inducing spectrum overlapping are analysed theoretically, and simple physical explanation and analytical deduction are given. Secondly, aiming to suppress spectrum overlapping and improve measurement accuracy, the influence of spatial carrier frequency of projection grating on them is analysed. A method of increasing the spatial carrier frequency of projection grating to restrain or reduce the spectrum overlapping significantly is proposed. We then analyze the mechanism of how the spectrum overlapping is reduced. Finally, the simulation results and experimental measurements verify the correction of the theory and method proposed.     

New theoretical analysis ofv 2 0→1Q-bands of ammonia

Summary The analysis ofQ-band infra-red transitionsv ₂0→1 of ammonia has been performed by using existing data and a simple polynomial expansion up to the tenth order ofJ andK. The lines withK=3 require an additionalJ-dependent term because of theK-splitting effect. In this manner, the spectrum has been reproduced within the accuracy of the experimental data. New experimental lines withJ≦20 have been reported or assigned. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Detection of a directly modulated terahertz light with quantum-well photodetector

We demonstrate a wireless transmission link at 3.9 THz over a distance of 0.5 m by employing a terahertz （Hz） quantum-cascade laser （QCL） and a THz quantum-well photodetector （QWP）. We make direct voltage modulation of the THz QCL and use a spectral-matched THz QWP to detect the modulated THz light from the laser. The small signal model and a direct voltage modulation scheme of the laser are presented. A square wave up to 30 MHz is added to the laser and detected by the THz detector. The bandwidth limit of the wireless link is also discussed.     

Physics possibilities at a linear collider

We review some recent studies about the parameter determination of top quarks,W bosons, Higgs bosons, supersymmetric particles and in the ADD model of extra dimensions at a linear collider.     

New band systems of NiBr molecule in visible region

Thermal emission spectrum of NiBr molecule excited by vacuum graphite tube furnace revealed the existence of ten new band sub-systems in the region λλ 5540-4720 Å which were attributed toA→X,B→X,C→X andD→X transitions. Vibrational analysis was carried out for each of the systems mentioned above.A ² Δ has been suggested as the ground state of NiBr molecule with an electronic interval of about 533 cm^?1. Transitions responsible for NiBr spectrum appear to be of the type²π–²Δ and²Δ–²Δ.     

New band system of MnSe molecule

Thermal emission spectrum of MnSe molecule, excited in high temperature graphite furnace, has been photographed in the spectral region λλ4150–5800 Å at a reciprocal linear dispersion of 7.3 Å/mm. The study reveals the presence of two band systems viz.A–X andB–X in whichB–X is entirely new. While the systemA–X consists of 29 bands, the new systemB–X comprises of 24 single headed and red degraded bands. Vibrational analysis performed suggested that both the systems involve ground state⁶Σ with a vibrational frequencyω″ _e =361.0 cm^?1. Transition responsible for MnSe spectrum appears to be of the type⁶Σ–⁶Σ. An estimation of the ground state vibrational frequency for MnTe molecule gives rise to its value as 280 cm^?1.     

一种基于CCD的实时测量光栅常数的方法

光栅常数是检验光栅质量的重要参数之一.该文介绍了一种实时检测光栅参数的方法,即利用面阵CCD采集光栅衍射图像信息,通过计算衍射±1级光斑与主极大光斑的能量比得出光栅常数.这种方法具有检测速度快、系统简单、精度高等特点,可用于生产线上光栅的实时检测.     

Spectral signature of single-grain quartz using a high-sensitivity TL imaging system

The spectral signature of individual quartz grains were measured using a high-sensitivity thermoluminescence imaging system based on a charge-coupled device (CCD) camera and custom optics. Luminescence emission behaviour was characterised for individual quartz grains (180–212 μm), with single grains shown to emit luminescence strongly across multiple signal bands. The spectral profiles of three quartz samples from contrasting geological contexts were then compared, with clear distinction in the spectral signatures of individual grains originating from single deposits within each provenance.     

Experimental study of corona jet produced from a circular tube fitted with a nozzle

The flow characteristics of a corona jet, which is produced from a single needle electrode positioned at the centerline of a circular tube fitted with a grounded stainless-steel nozzle at one end of the tube, is experimentally evaluated. Six nozzles with two diameter ratios and three taper angles are evaluated for their effectiveness in accelerating the jet produced by corona discharge with positive polarity. To determine the maximum jet velocity and volume flow rate, experiments have been conducted at a voltage ranging from corona onset (5 kV) to sparkover (approximately 12.5 kV) at an increment of 2.5 kV. The results show that the jet velocity increases with the applied voltage. The maximum velocity occurs at the center line but its value decreases as the jet expands downstream. In addition, the results show that a nozzle with a smaller diameter ratio does not always perform the best in accelerating the flow or producing the maximum volume flow rate. The nozzle's taper angle further accentuates the result produced by the diameter ratio. The implications from the present results for actual applications are provided.     

Optimal processing of noisy images in a photodetector with limited dynamic range

A study aimed at optimizing noisy image processing under conditions of strong additive noise has been performed. An algorithm of optimal signal processing was developed and a possibility of improving image quality due to the subtraction of excess additive noise (which limits the photodetector dynamic range) was substantiated. The possibility of technical implementation of noise subtraction due to forced recombination of charge carriers in the photodetector is experimentally confirmed. The proposed approach to design processing systems makes it possible to improve the quality of recorded images under noisy conditions without any changes in the photodetector design.     

New reformulation of the Fourier modal method with spatial adaptive resolution for multilayered metallic strip grating

The parametric formulation of the combined boundary conditions method (CBCM) with spatial adaptive resolution is extended to multilayered structures of strip gratings. Furthermore, it is shown that it is not necessary to solve the eigenvalue problem in all the layers of these structures; leading to drastic reduction of the computational load.     

Exploitation of inter-track interference in a shingled replay system

The expected increase in areal density in hard drives will require very narrow tracks. Tracks which are of a similar width to the read head and which are not separated by guardbands normally suffer from large inter-track interference (ITI) or crosstalk. Here, we show that it is possible to read from tracks which are not separated by guardbands and that are narrower than the head. In addition to the significant increase in areal density obtainable by reducing the unrecorded area of the disk and narrowing the tracks, such a system would also lead to a decrease in data retrieval times. We have identified across-track magnetization constraints for future coding across three adjacent tracks so that it will be possible to read from tracks which are only 73% as wide as the read head. Reading from tracks not separated by guardbands which have been written under these constraints yields an increase in track density of at least 47% greater than that possible in conventional drives.     

多通道CCD摄像机的数据采集和图像显示

针对多通道CCD摄像机 ,提出了一种多线程数据实时存储的方法。利用多线程提高硬盘读写速度 ,实现高速、大容量CCD摄像机数据的硬盘实时存储 ,并利用定时中断将多通道信号定时分块存储入硬盘 ,存储的CCD摄像机数据被转换为图像文件加以显示。系统的CCD摄像机通道达到 5个 ,每个通道的数据率达到 10MBit/s。通过实验 ,验证了该方法的正确性和有效性