锁频点连续可调的激光器稳频技术

实现了利用铯原子圆二向色性激光稳频(DAVLL)技术保证频率的非共振锁定并连续可调。介绍了DAVLL技术用于稳定激光频率的基本原理,指出由于Cs原子复杂的能级结构,导致简单的DAVLL技术此处不再适用,并且发现稳频曲线的零点与磁场强度的大小有关;利用饱和吸收光谱测量磁场对DAVLL谱线鉴频零点的影响,发现激光频率在以Fg=4→Fe=5跃迁红失谐105MHz为中心50MHz范围内线性可调,频率稳定度可达3MHz。     

480nm激光器的双光子DAVLL谱稳频

480nm激光的稳频对于实现铷原子从基态双光子相干激发到里德堡态必不可少。本工作基于梯形构型下的电磁诱导透明现象,一种新的480nm激光器稳频技术采用偏振谱稳频的780nm激光作为探测光而480nm激光则作为耦合光,在外加偏置磁场作用下产生的双光子双色原子气体激光锁频（DAVLL）谱方法,将该谱信号通过比例-积分-微分电路后反馈回480nm激光器即可实现稳频。在频率锁定后,480nm激光器和780nm激光器长时间稳频的总线宽为1MHz左右。     

采用射频调制实现对单频激光器频率噪声的抑制

在使用铷原子饱和吸收谱线作为激光频率参考进行稳频的激光稳频系统中,环路带宽是影响激光输出频率噪声的重要因素之一。对激光稳频系统中限制环路带宽的主要因素进行分析,使用射频调制信号直接调制商用外腔半导体激光器的高速电流调制端来对激光稳频系统的环路带宽进行拓展。根据对稳频环路的分析,合理设置反馈电路,实现激光稳频。使用低频谱分析仪对稳频后的鉴频信号进行分析,发现带宽拓展后,在傅里叶频率为5kHz处对频率噪声的抑制度达到了20dB以上。通过将该稳频激光器输出的激光与锁定在极稳恒温晶振上的飞秒光学频率梳进行拍频,测量了该稳频激光相对光梳的频率噪声,测量结果与直接分析鉴频信号的结果吻合。经过测量,通过拓展带宽抑制频率噪声,稳频激光器的短期频率稳定度得到改善。最后,测量了稳频激光相对于锁定在恒温晶振上的飞秒光学频率梳的频率稳定度,Allan方差在平均时间1s时达到4.52×10~(-12),在平均时间20s时达到1.65×10~(-12)。     

用于原子重力仪的外腔半导体激光器的两种稳频方法比较

在铷原子气室中实现了饱和吸收谱稳频法和消多普勒的双色谱稳频法,以给在建的原子干涉重力仪系统选择合适的激光稳频方法。介绍了两种稳频方法的基本原理及实验细节。通过调整光路设计、自制低噪声光电探测器以及应用数字锁定模块,获得了良好的鉴频误差信号。每种方法都搭建了两套稳频系统并在3 000 s采集时间内保持锁定。激光器在经饱和吸收法和消多普勒双色谱法锁定后,激光频率波动分别为16.2 kHz和31.4 kHz,相应于在10 s采样时间下分别获得4.2110-11和8.1810-11的频率稳定度;相比之下,激光器自由运转时,频率波动和稳定度分别为629 kHz和1.6410-9。在原子重力仪系统小型化的需求下详述了两种稳频方法的优缺点,比较而得消多普勒的双色谱稳频法在原子干涉重力仪的小型化模块化发展方向不失为具有潜力的一种选择。     

LD相对于铯原子超精细跃迁线的偏频锁定

对于单纵模半导体激光器（ＬＤ）,应用往返两次通过一个声光频移系统的方法,结合铯原子饱和吸收稳频技术,实现了激光频率相对于铯原子Ｄ２线６２Ｓ１／２（Ｆ＝４）→６２Ｐ３／２（Ｆ′＝５）超精细跃迁的偏频锁定。其特点是可通过调谐声光频移系统的工作频率方便地改变偏频量,而不需要对光路进行再调整     

原子干涉仪中拉曼激光的相位-频率双调制稳频

为降低拉曼激光的频率噪声,提出了一种相位-频率双调制稳频技术。用光纤电光相位调制器对激光进行调制并产生大失谐边带;用射频信号对光纤相位调制器的微波驱动信号进行频率调制,通过锁相放大法将一个大失谐边带锁到铷原子的饱和吸收谱线上。利用该技术实现了拉曼种子激光的稳频和2 GHz的移频,拉曼激光的线宽大幅压窄到56 kHz,预期拉曼激光频率噪声引起的原子干涉重力仪的单次测量噪声可降低到7×10-9/s2。     

~(52)Cr原子束激光生荧光稳频技术

通过分析52Cr原子光刻对激光系统的技术要求,详细介绍了一种基于原子束激光感生荧光(LIF)光 谱技术的稳频方法。     

利用锁相飞秒激光对碘分子R(59)8-4超精细跃迁的绝对频率测量

介绍了633 nm半导体激光频标系统,高重复频率锁相飞秒激光器系统和绝对频率测量系统的建立以及测量碘分子超精细跃迁绝对频率的系统方案.633 nm半导体激光频标采用三次微分稳频方法,将激光频率锁定在碘分子谱线上,获得0.5 mW的稳频激光输出.飞秒激光稳频系统通过锁相电路将飞秒激光的高重复频率(760 MHz)和初始频率稳定在微波频率标准上,从而得到稳定的飞秒光梳,其稳定度优于6.44×10-13.在此基础上建立了绝对频率的直接测量系统,即利用波长计直接测量光梳的齿数n,并通过拍频法,测出633 nm半导体激光频标与飞秒光梳的差频,从而计算出相应谱线的绝对频率.这样,通过锁相飞秒激光器,建立了微波频率标准到光学频率标准的传递,为进一步的基础研究工作奠定了基础.     

基于微型控制器的原子光刻系统自动化控制研究

原子光刻系统的设备庞大而复杂,在实验过程中温度及稳频光等参数都需要监视和控制。针对目前多采用人员值守的方式对设备进行操控导致实验效率低下的现状,介绍了原子沉积原理和原子沉积实验装置的构造及主要功能,提出了原子沉积实验装置中温度控制方案和稳频光的差分信号数据采集方案。通过完成对温度信号和稳频光信号等实验数据的自动采集与记录,实现了原子光刻系统的温控系统自动化和激光稳频系统的远程控制。该方案不仅提高了实验效率,而且对USB开发人员和自动化研究人员也具备一定的参考价值。     

利用全光纤环形谐振器实现对单频激光器频率噪声的抑制

给出了利用全光纤环形谐振器实现对激光器频率噪声抑制的原理和实验结果。采用Pound-Drever-Hall的方法对锁定在铷原子吸收谱线上的激光进行稳频,实现了饱和吸收光谱与光纤环形谐振器双回路锁定。通过外差式马赫-曾德干涉仪来测量锁定后的激光器频率噪声发现,在频率100 Hz时,光纤环形谐振器对频率噪声的抑制度超过了40 d B。在1 Hz处,稳频激光器的频率噪声小于100 d B Hz2/Hz,其抑制度达到60 d B。     

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.     

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.     

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.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Technology innovation and process integrations for sub-100nm gate patterning

This paper presents a brief overview of the Applied Centura(R)DPS(R)system,configured with silicon etch DPS Ⅱ chamber, with emphasis on discussing tuning capability for CD uniformity control. It also presents the studies of etch process chemistry and film integration impact for an overall successful gate patterning development. Discussions will focus on resolutions to key issues, such as CD uniformity, line-edge roughness, and multilayer film etching integration.     

White organic light-emitting devices based on fac tris（2- phenylpyridine） iridium sensitized 5,6,11,12-tetraphenylnap -hthacene

We have fabricated the white organic light-emitting devices （WOLEDs） based on 4,4＇ -bis（2,2 -diphenyl vinyl）-1,1＇ - biphenyl （DPVBi） and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene （rubrene）. The device structure is ITO/2T-NATA （20 nm）/NPBX （20 nm）/CBP： x%Ir（ppy）3：0.5% rubrene （8 nm）/NPBX （5 nm）/DPVBi （30 nm）/Alq（30 nm）/LiF（0.5 nm）/A1. In the devices, DPVBi acts as a blue light-emitting layer, the rubrene is sensitized by a phosphorescent material, fac tris （2-phenylpyridine） iridium [Ir（ppy）3], acts as a yellow light-emitting layer, and N,N＇ -bis- （1-naphthyl）- N,N＇ -diphenyl -1, 1＇ -biphenyl-4,4＇ -diamine （NPBX） acts as a hole transporting and exciton blocker layer, respectively. When the concentration of Ir （PPY）3 is 6wt%, the maximum luminance is 24960 cd/m^2 at an applied voltage of 15 V, and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.     

小角度扩展相关性近似算法分析

本论文提出一种在多天线MIMO信道相关性建模中小角度扩展近似理论算法,并应用于分析MIMO系统性能。分析中分别对三种不同角能量分布情况下的空间相关性研发快速近似计算法,并同时提出双模(Bi-Modal)角能量分布情况下的近似运算。通过分析这些新方法的近似效率,可以得到计算简单、复杂度低、而且符合实际的MIMO相关信道矩阵,对系统级的快速高效计算法的研究和系统级的评估以及误差分析具有重要的意义。     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.