体布拉格光栅外腔半导体激光器前端面反射率对输出光谱特性的影响

采用反射式体布拉格光栅(VBG)实现半导体激光锁频是激光技术应用中的关键技术之一，进一步压窄半导体激光的输出光谱线宽、提高外腔效率是研究重点。采用微通道水冷半导体激光模块，利用衍射效率为18%的VBG构建激光外腔，分析了前端面反射率分别为0.02%、0.20%、0.40%时的输出光谱与外腔效率。研究结果表明，半导体激光前端面反射率的降低能够进一步优化半导体激光器的输出光谱，提高外腔效率，压窄输出光谱线宽，实现大驱动电流范围的激光锁频。对于前端面反射率为0.02%的半导体激光器，激光输出中心波长锁定在779.8 nm处，光谱线宽压缩至0.08 nm，温漂系数为6.25 pm·℃^-1，电流漂移系数为0.9 pm·A^-1，外腔效率达到106%，连续输出功率达到127 W。     

带间耦合多有源区大功率980nm半导体激光器

提出利用隧道结实现带间耦合再生多有源区大光腔大功率的半导体激光器。该激光器能够在小的电流下输出大的光功率；同时可以使出光端面成倍增加，减少了端面光密度，克服端面灾变性毁坏（COD）。由于耦合形成大光腔，提高了光输出的质量。制备4个有源区带间耦合大功率980nm半导体激光器。在2A注入电流下输出功率5W，阈值电流172mA，斜率效率3.24w/a，阈值电流密度273A/cm^2。     

端面反射率对半导体激光器单模工作性能的影响

本文利用半导体激光器多模速率方程组的隐式解析解，从理论上了端面反射率对半导体激光器单模工作性能的影响，结果表明，在相同的输出功率下，端面反射率越低，单模工作性能越差，与Ｅｔｔｅｎｂｅｒｇ等人通过实验研究所得的结论相同。     

端面反射率对半导体激光器微分功率特性的影响

从理论和实验上研究了端面反射率对半导体激光器微分输出功率等特性的影响。研究表明,用镀膜方法适当地降低半导体激光器输出端面反射率,有助于增大输出功率和提高外量子效率。     

GaAlAs/ GaAs 半导体功率放大激光器的研究

研究一种GaAlAs／GaAs材料的高功率半导体功率放大激光器(LD—SLA)。器件为双异质结增异导引氧化物条形结构。采用直接耦合方式将半导体激光器(LD)与半导体功率放大器(SLA)集成一体，使单管芯输出光功率提高一个数量级。并在器件端面镀高反射膜和增透膜，使器件端面的反射率和透射率由不镀膜时的29％、71％提高到90％以上，进一步提高激光输出。保护器件端面、提高器件使用寿命。     

改进型1.06μmNd：YAG激光器泵源

本文报道了用改进的液相外延技术制作的ＩｎＧａＡｓＰ／ＧａＡｓ分别限制单量子阱激光器，将其端面分别蒸镀增透膜和高反膜后，激光器输出功率提高近１倍，因此用此ＬＤ端面泵浦Ｎｄ：ＹＡＧ激光器，当泵浦源输出２．７Ｗ时，得到了７００ｍＷ连续激光输出。     

掺镱双包层光纤激光器多波长输出性能分析

从理论上分析了由F-P滤波器实现的多波长双包层光纤激光器(DCFL)的边界条件和输出功率,在考虑了F-P滤波器中双色镜反射率的波长依赖关系的前提下,对影响多波长输出功率和消光比的参数如双色镜和光纤出光端面的反射率、抽运功率等进行了研究。结果表明,光纤出光端面的反射率存在一个最佳值,再配合适当的双色镜反射率,能使多波长输出的功率和消光比达到很好的均衡。适当增大抽运功率也能优化多波长输出功率和消光比。通过控制F-P滤波器的腔长,能够调节多波长输出的数目。     

GaAlAs/ GaAs 半导体功率放大激光器的研究

研究一种GaAlAs/ GaAs 材料的高功率半导体功率放大激光器(LD - SLA) 。器件为双 异质结增异导引氧化物条形结构。采用直接耦合方式将半导体激光器(LD) 与半导体功率放大器(SLA) 集成一体,使单管芯输出光功率提高一个数量级。并在器件端面镀高反射膜和增透膜,使器件端面的反射率和透射率由不镀膜时的29 %、71 %提高到90 %以上,进一步提高激光输出。保护器件端面、提高器件使用寿命     

一种可降低Littman-Metcalf光栅外腔半导体激光器衍射损耗的结构设计

基于原有Littman-Metcalf型光栅外腔半导体激光器的工作原理,设计了一种可以降低衍射损耗的外腔结构。在Littman-Metcalf结构的基础上增加一个反射镜,将闪耀光栅二次衍射产生的零级衍射光反馈回半导体激光器本征腔。推导了新结构模型外腔损耗的表达式,通过等效腔的概念对两种结构激光器的外腔损耗、阈值电流、输出线宽以及输出功率进行了仿真分析。结果表明：将二次衍射产生的零级光反馈回有源区可有效降低Littman-Metcalf结构激光器的外腔损耗,提高了系统的耦合效率,从而降低阈值电流,提高了激光器的输出功率。同时,由于提高了外腔反射效率,该外腔结构进一步压窄激光器的输出线宽。对影响低损耗Littman-Metcalf外腔激光器输出线宽以及输出功率的因素(端面反射率、内外腔长、闪耀光栅衍射效率以及反射镜反射率等)也进行了仿真分析,为后期激光器制作提高了理论指导。     

光纤端面反射率对光纤光栅外腔半导体激光器的输出影响

为了实现光纤光栅外腔半导体激光器良好的单纵模输出,通过加入空气间隙区改进了基于射线法的光纤光栅外腔半导体激光器理论模型,并结合稳态速率方程研究了小注入情况下,光纤端面反射率对激光器输出特性的影响。仿真结果表明,在光纤端面反射率与光栅反射率可比拟的情况下,减小光纤端面反射率,可增大主模与其他波长模式的损耗差异,加强光纤光栅的选模作用,更好的实现单纵模输出,但同时也会增大激光器的阈值电流。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.