基于双偏振调制器的相位编码技术研究

提出了一种新型的基于双偏振调制器(Polm)实现相位编码的方法,不仅可以保证编码信号180°相移,而且可以实现微波编码信号的宽带可调谐。当微波信号加载到第1个Polm时,从第1个Polm输出的信号是两路偏振垂直、相位互补的信号;该信号经过带通滤波器(BPF)滤除下边带,只留下两路偏振正交的载波和上边带,再调谐偏振控制器(PC),使得两路正交的信号进入到第2个Polm里,这时第2个Polm起着光开关的作用;根据加载的射频信号的幅度不同,经过检偏器(Pol)检偏,可以分别实现两路不同的偏振信号输出,由于两路上边带的相位是互补的,最终可以实现可调谐相位编码信号的产生。     

基于偏振调制的可变系数微波光子滤波器

基于偏振调制器(PolM)设计并实现具有可变系数特 性的可调谐微波光子滤波器,通过理论计算与实验证 实了设计方案的可行性。PolM可以对输入的微波信号实现两路正交反相的相位调 制,经强度调制转 换后,可以拍频恢复出原来的微波信号。仅需通过调节偏振控制器(PC)控制光信号的检偏方 向,即可实现恢复 出的微波信号π相位变化,进而实现滤波器抽头系数的正负变化。利用偏振分束器(PBS)实 现两路光信号检偏和 合并的同时,能够有效地避免两路光信号之间的干涉。通过调节光路中的光可调时延线(OTD L)改变两路光信号 间的时延差,能够改变滤波器的自由光谱范围(FSR),实现滤波 器的可调谐。通过实验验证了时延差分别为300ps和400ps 两种情况下正系数和负系数微波光子滤波器的频率响应,与理论计算值相吻合,验证了方案 正确性。     

超宽带信号的产生及光纤传输的研究

提出了一种新的超宽带(UWB)脉冲产生的方法,并对其产生的数学原理进行了分析和实验验证。经过高斯信号调制的偏振控制器(PC)可以产生两个相位互补的相位调制信号,先通过PC调节两个正交的相位调制信号的静态相移,再经过偏振分束器(DBS)检偏后可以得到两路相位互补的高斯信号或二阶高斯信号,最后将这两路信号延时然后再经过偏振合路器(PBC)就可以分别得到一阶或三阶高斯信号。由于这3种脉冲的产生方式不同,频带宽度不同,在光纤中传输时对色散的容忍度也不一样,因此仿真分析了色散对这3种UWB信号传输特性的影响,得出了三阶高斯信号最适合UWB传输。     

一种可重构双输出微波光子变频器的设计与仿真

提出了一种可重构双输出微波光子变频器,该变频器可以实现上变频、下变频和同相/正交（I/Q）上变频。通过改变偏振复用-双平行马赫曾德尔调制器的驱动信号,可以重构生成上、下变频信号以及上变频的上、下边带信号或矢量信号,且能同时单独输出两路变频信号。利用偏振控制器在正交偏振方向上巧妙地消除了本振信号的正/负一阶光边带,避免了滤波器的使用,进而实现了频率的大范围可调谐。仿真结果表明：所提变频器可在1～59 GHz带宽范围内单独输出两路任意频率的信号,杂散边带抑制比大于30 dB;加载I/Q基带信号可以进行I/Q上变频,生成两路高频64阶正交振幅调制（64QAM）矢量信号,误差矢量幅度小于3.5%。所提变频方案能消除光纤色散引起的功率周期性衰落效应,系统的无杂散动态范围为107.1 dB·Hz2/3。此外,分析了直流偏置电压漂移、电移相器相位不平衡、偏振控制器偏振漂移等非理想因素对变频器性能的影响。     

基于PolM的可调谐相位编码信号发生器设计

采用双平行偏振调制器,在不使用任何光或电滤波器的条件下,利用倍频操作在双平行偏振调制器和混合器工作频段内产生相位编码信号。在10Gb/s的编码速率下,仿真实验实现了10~40GHz范围的调谐,结果表明,在光生频率内该相位编码微波信号具有良好的大范围可调谐性能。     

一种基于半导体光放大器的Ku波段可调谐光电振荡器

基于半导体光放大器(SOA)的非线性偏振旋转效应,提出了一种可调谐双环路光电振荡器(OEO),并从理论上分析了这种设计的基本原理。实验测得了振荡频率为12.978 GHz的微波信号的频谱图和相位噪声图,并且在Ku波段通过直接调节SOA注入电流得到调谐范围为40MHz,调谐步长约为2MHz的微波信号输出。在整个调谐范围内,输出微波信号的相位噪声在偏离中心频率10kHz处低于-75dBc/Hz。     

基于偏振调制器和单模光纤的微波瞬时频率测量研究

提出了一种基于偏振调制器(PolM)实现微波信号 的瞬时频率测量(IFM)方法并进行了实验验证。它采用PolM同时实现相位调制和强度调制, 利用1个光源和1段单模光纤(SMF)保持光路中功率稳定,通 过光纤的色散将微波信 号频率映射到功率上,最后经过光电探测器(PD)探测并计算出两路电信号的功率比。这个功 率比一一对应于输入的微 波信号频率,最终能够测得所输入的微波信号频率。实验结果表明,它不仅可以实现1～12GHz宽带范围 内IFM,测量精度可以达到0.2GHz,而且能够同时保证 所测量的微波信号频率的系统误差小,稳定度好。     

一种60GHz毫米波全双工光纤无线通信系统

为了实现有线信号和无线信号的同时传输,采用将有线信号和无线信号分别在两个正交的偏振态中构造混合网络的方法,用非对称输入的双臂马赫-曾德尔调制器来产生无线信号中的毫米波;利用相位调制器实现差分相位键控调制格式,以便在上行链路中实现载波重用有线信号,分别将调制后两个正交偏振态信号耦合到同一光波长上经过光纤传输至基站。在基站处将两个正交偏振态的信号分离,携带无线信号光载波经光电检测放大后由天线传输出去,而携带有线信号光载波分为两路,一路经过平衡检测器检测得到有线信号,另外一路应用到上行链路中实现载波重用。通过OPTICSYSTEM软件进行了理论分析和实验验证,得到了10Gbit/s有线信号和60GHz无线信号通过光纤传输50km后的眼图。结果表明,该方案传输效果很好。     

基于激光外调制的频率可调谐光电振荡器

为了实现光电振荡器(OEO)输出频率的可调谐,提出了一种基于外调制激光的频率可调谐光电振荡器。此方案在单环OEO的基础上增加一个由微波滤波器、电衰减器、电放大器和电移相器构成的电增益选频腔,通过调节电移相器的偏置电压可以等效改变电选频腔的腔长,从而改变其输出微波信号的频率;同时调节光延时线来改变光电振荡器的起振模式,通过电增益选频腔信号与光电振荡器自由振荡信号的电注入锁定,即可实现频率可调谐的光电振荡器,其输出信号的频率由锁定OEO模式的电增益选频腔决定。实验结果表明,本方案产生了频率调谐范围为10.05 GHz~10.09 GHz、调谐步长为400 kHz的输出信号,频率在40 MHz的范围内连续可调谐。在输出频率为10.0519 GHz时,其边模抑制比为60 dB,相位噪声为-115 dBc/Hz @10 kHz。该方案结构简单,既保留了单环OEO低相位噪声的优势,又能有效抑制边模,为实现频率可调谐OEO提供了一种新的方法。     

光电振荡环路的微波光子变频与移相技术研究

微波光子变频与移相技术是微波光子雷达的两个关键技术,若在实现微波光子变频的同时完成移相,可以大幅降低微波光子雷达系统的复杂度和体积。本研究基于光电振荡环路提出一种可同时完成微波光子变频与移相的方法,利用光电振荡环路对基频微波信号进行上变频,通过改变光电振荡器的输出频率,实现1.6～21.16GHz可调谐上变频;调节可调谐激光器的输出波长,利用色散补偿光纤的延迟效应等效改变上变频信号的相位,调谐范围可达50.4°。该方案将微波光子变频与移相技术结合,在拓展光电振荡器应用范围的同时,对微波光子雷达的实用化也有一定借鉴意义。     

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.     

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.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

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