温控体布拉格光栅外腔单管半导体激光器

为了研究铷蒸气激光中的线宽匹配技术,基于半导体制冷片(TEC)的温度控制技术设计了窄线宽可调谐单管半导体激光器.利用半导体激光器的温度漂移特性,使LD的激光光谱中心波长在780 nm附近(工作温度-6℃),采用体布拉格光栅(VBG)外腔结构改善了LD的激光光谱,获得了功率1.448 W线宽0.13 nm的激光输出.通过调节VBG的温度,LD波长可从779.28 nm调谐至780.13 nm,调谐范围达850 pm.     

连续工作的体布拉格光栅外腔半导体激光器的温度特性

对体布拉格光栅(VBG)作为波长选择元件的外腔半导体激光器的波长锁定进行了实验研究,报道了连续运转输出功率达43.5 W的半导体激光器阵列的体布拉格光栅波长锁定实验结果,给出了不同热沉温度下的稳定的波长锁定结果,说明采用体布拉格光栅外腔将减小半导体激光器的温控压力。实验中发现,随着注入电流的增大,输出激光功率逐渐增强,锁定的激射波长向长波长方向偏移。在输出功率为34.5 W时,波长红移约0.56 nm。这一移动与实验测量的体布拉格光栅的温度特性相吻合。连续和高占空比运行、高输出功率情况下,在器件的设计和使用时应该考虑这一效应。     

反射式体布拉格光栅设计及其在激光器中的应用研究

半导体激光器的发射波长随工作电流和温度的改变而变化,从而影响输出激光的有效线宽和波长稳定性,无法满足固体激光器中增益介质对泵浦源波长和线宽的要求。使用自主研发的衍射效率为9.9%的878 nm反射式全息体布拉格光栅(volume Bragg grating,VBG)作为半导体激光器的反射腔镜,可以将激光发射波长锁定在设计的878 nm附近,输出线宽仅为0.3 nm,波长电流漂移系数为0.015 nm/A,温度漂移系数为0.0075 nm/℃。利用波长锁定的半导体激光器作为泵浦源、自主研发的衍射效率为98.71%和94.32%的1 064 nm VBG作为前后腔镜以及掺杂浓度为0.3%的Nd∶ YVO₄晶体作为增益介质搭建全固态激光器,经过空间光路的调试,获得中心波长1 064.2 nm、线宽0.29 nm的连续稳定激光输出。     

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。     

高功率半导体激光器线阵列的波长锁定技术

高功率半导体激光器光谱随温度和工作电流的变化比较大,光谱线宽比较宽,这些缺点直接限制了其实际应用.因此,高功率半导体激光器波长稳定技术的研究是激光领域的一个重要研究方向.对波长稳定技术进行研究.实验用体布拉格光栅(VBG)作为反馈元件与高功率半导体激光器线阵列,构成可以对其波长进行锁定的外腔激光器.分析了外腔激光器的波长锁定效果与高功率半导体激光器工作电流、冷却温度、工作电流的占空比和"smile"现象等因素的关系.研究结果表明,高功率半导体激光器的工作电流、冷却温度、工作电流的占空比会影响其激射波长,当激射波长与VBG的布拉格波长差值小于3.0 nm时,可以得到较好的波长锁定效果,而阵列本身的"smile"现象对其波长锁定的影响不大.     

体布拉格光栅反射率对外腔半导体激光阵列输出光谱的影响

采用记录在光致热敏折射率玻璃中的反射型体布拉格光栅作为反馈元件构成外腔半导体激光阵列,对其输出光谱特性进行了实验研究,分析了快轴准直透镜的位置对外腔反馈耦合效率的影响。实验结果表明,在体布拉格光栅外腔反馈作用下,半导体激光阵列输出光谱中心波长得到锁定,同时输出线宽显著变窄。重点研究了体布拉格光栅的反射率对外腔反馈半导体激光阵列输出光谱特性以及激光器效率的影响。实验结果表明,体布拉格光栅反射率的增加可提高半导体激光阵列内腔模式的抑制效果,提高输出光谱对比度,减小输出光谱线宽。使用反射率为30%的体布拉格光栅,可将半导体激光阵列的输出波长锁定在808nm附近,输出光谱线宽压缩至0.18nm。外腔半导体激光器的输出功率达24.8W,效率为82.6%。     

体布拉格光栅外腔半导体激光器温度特性研究北大核心CSCD

使用COMSOL软件对体布拉格光栅(volume Bragg grating, VBG)外腔半导体激光器进行稳态热分析模拟仿真,研究VBG对半导体激光器的温度特性的影响。利用15%、20%两种VBG对888 nm半导体激光器进行外腔锁模,测试并分析外腔锁模条件下半导体激光器的输出特性和温度特性。结果表明,VBG外腔结构能够改善半导体激光器的光谱特性,提高半导体激光器的工作温度。在25℃条件下,当采用15%衍射效率的体光栅进行外腔锁模时,最大输出光功率为10.7 W,输出波长稳定在888 nm,光谱线宽为0.3 nm。     

双端抽运的30 W光纤激光器实验研究

报道了双端抽运连续输出的掺Yb^3 双包层高功率光纤激光器。实验采用了中心波长在975nm附近的两种输出形式的半导体激光器(LD)作为抽运源，测量了不同抽运条件下的输出功率特性和光谱特性。在仅尾纤输出的半导体激光器抽运下获得了斜率效率为42％，峰值波长为1103．8nm的9．2W激光输出；在仅准直输出的半导体激光器抽运下获得了斜率效率为57％，峰值波长为1104．4nm的20．0W激光输出；当两个半导体激光器在双端同时抽运时，获得光纤激光最大输出功率为30．6W，输出峰值波长为1108．4nm，以及49％的总体光一光转换效率。     

10W级高效率单模中红外2.8μm光纤激光器

报道了高功率、高效率单模中红外2.8 mm波段光纤激光器。采用中心波长为975 nm的半导体激光器(LD)抽运高掺铒氟化物双包层光纤Er∶ZBLAN,室温下实现了2.8 mm激光功率超过9 W中红外光纤激光连续输出。激光器最大输出功率为9.2 W,斜率效率为24.8%,工作阈值约为1.0 W,中心波长为2.79 mm,激光工作模式为单模,光束质量M2因子小于1.2。     

双波长可调外腔半导体激光器

提出了一种基于体布拉格光栅（VBG）和横向啁啾体布拉格光栅（TCVBG）组合的双光栅外腔半导体激光器,该外腔半导体激光器采用反射率15%的体光栅和反射率17%的啁啾体布拉格光栅作为反馈元件和模式选择元件,实现特定波长的选择和调谐,实验研究了外腔激光器的功率-电流特性、光谱特性和波长调谐特性。实验结果表明:双光栅外腔半导体激光器最大输出功率为1.96 W,斜率效率为0.94 W/A,外腔效率达到78%。输出光谱为双波长,一个波长为808.6 nm,另一个波长连续可调,通过改变横向啁啾体光栅的位置,该波长可从800 nm调谐至815 nm,可调范围达15 nm,在整个可调范围内两个波长的谱线宽度（FWHM）均小于0.3 nm。     

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.     

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.     

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.     

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.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks     

Call for Papers—Feature Topic,Vol.12,No.7,2015

正Information Centric Networking Information-Centric Networking(ICN) is an emerging direction in Future Internet architecture research,gaining significant tractions among academia and industry.Aiming to replace the conventional host-to-host communication model by a data-centric model,ICN treats data content as the first