1.3μm偏振无关半导体光放大器单片集成模斑变换器

用金属有机化学气相外延生长并制作了 1.3μm脊型波导偏振无关半导体光放大器集成模斑变换器 ,器件有源区为同时采用压应变量子阱和张应变量子阱的混合应变量子阱结构以获得TE和TM偏振模式的增益平衡 ,模斑变换器采用一种新型脊型侧向锥形波导结构 ;集成模斑变换器的半导体光放大器远场发散角为 12°× 15° ,接近圆形光斑 ,与平头标准单模光纤耦合损耗为 - 2 .6dB ,在水平和垂直方向上的 - 1dB耦合对准容差分别为± 2 .3μm和± 1.6 μm ;在 2 0 0mA偏置电流下 ,半导体光放大器小信号增益近 2 4dB ,在 12 80～ 1340nm波长范围内偏振灵敏度小于 0 .6dB。     

仅有相邻波导耦合的定向耦合器的一般解法

应用切比雪夫多项式 ,求得了仅有相邻波导耦合的 (N +1)× (N +1)定向耦合器在弱耦合、无损耗和忽略正交偏振模场分量间耦合的情形下波导耦合方程的通解。列出线形排列 2× 2 ,3× 3,4× 4定向耦合器的解的表达式 ,并对环形排列 3× 3定向耦合器的解作了较详细的分析     

用于波导阵列——光纤阵列自动对接的多目标演化算法的研究

开发设计了一种新的列阵自动对接方法,该方法将多目标演化法导入光纤—光波导列阵—光纤列阵的自动对接,并行操作次数较常规遗传法大幅减少.数值仿真表明,对于模场非对称因子为0.4%的单模波导列阵与光纤列阵的双芯对接,能实现0.04 dB的平均端面耦合损耗.用于1×8波导分支耦合器与通道间距误差在0.35 μm以内的光纤列阵对接,自动耦合仿真达到了小于0.1 dB的平均端面耦合损耗,最大值与最小值的差小于0.06 dB.     

浅海波导界面对点源振速方向的影响

采用“虚源法”分析计算了浅海波导环境中接收点处点源总振速方向与水平面夹角,侧重讨论确定性界面反射对总振速方向的影响。研究结果表明：总振速方向和接收点与声源的水平距离、两者深度,海底、海面特性以及声速剖面等有关。在等声速均匀浅海波导中,由于确定性界面反射的影响,当直达声掠射角为1°～50°时,合成总振速方向偏离直达声方向达1.5°～10.5°,声速剖面呈负梯度时,偏离程度更甚.     

一种基于斜光栅辅助的非对称耦合器型光分插复用器

提出了一种基于斜光栅辅助的非对称耦合器型光分插复用器。运用复合波导的三维正交模式,对器件的三种可能的结构进行了理论分析,选出粗波导光栅型结构。利用耦合模理论,模拟了斜光栅的耦合特性并对其倾斜角进行优化设计。通过回波峰值设计法,将器件的工作波长放在波分复用信道之内,回波峰值波长放在波分复用信道之外,使得器件的性能大有提高。模拟结果表明器件的串扰可达到-30 dB,回波损耗可达到-25 dB。同时,器件的关键工艺容差较大,易于批量化生产。当斜光栅的倾斜角度在2.5°到4.5°之间时,器件的串扰低于-28 dB,回波损耗低于-22 dB。     

光通信中的玻璃无源器件的制备与研究

本文报道了以高质量的BK7光学玻璃为衬底,通过稀释Ag+-Na+离子交换技术,制备出低损耗的表面条波导,并用近场法测量出条波导的模场分布曲线。给出光纤与波导耦合的失配损耗为0.54dB,条波导传输损耗为0.21dB/cm.以及在此工作基础上,成功地研制了适用于大容量相于光通信系统的1×2和1×4单模波导分束器。     

与纳米腔相耦合的一维波导中的单光子散射

我们研究了与包含三能级原子的纳米腔相耦合的一维耦合谐振器波导中的单光子散射,分别讨论了纳米腔与耦合谐振器波导局域和非局域的两种耦合方式.在局域耦合的情况下,不同偏振光子的透射及反射波谱关于共振点对称.而在非局域情况下,透射和反射系数中的对称性消失,峰和谷的位置向失谐较大处移动.耗散对单光子散射也会产生影响.     

Kr-CS2体系势能面及束缚态能级的理论研究

本文采用单双迭代(包括非迭代三重激发)耦合簇CCSD(T)方法，对C、S原子采用aug-cc-PVTZ基组，对Kr原子采用cc-PVTZ –DK基组，并且加上中心键函数(3s3p2d2f1g)，计算得到Kr-CS2体系的势能面。该势能面为T型结构，存在一个全局极小值和两个等价的局域极小值。全局极小值位于R =7.05 a0，θ= 90°处，势能值为-396.194 cm-1。两个局域极小值分别位于R = 10.15 a0，θ= 0°和180°处，势能为-243.647 cm-1。利用该势能面，通过数值求解相应的薛定谔方程，计算得出体系J≤10的束缚态能级及微波谱跃迁频率，并通过跃迁频率拟合得到相应的光谱常数。     

一种新型慢波结构TM01-TE11模式转换器的数值模拟

 设计了一种新型L波段慢波结构式圆波导TM₀₁-TE₁₁模式转换器，该转换器的尺寸为φ15.0 cm×40.8 cm，通过金属分割片将圆波导分成两个180°区域并在其中一个区域内设置半环形慢波结构。当TM01入射时，在两个区域内激励起扇形波导TE11模式，由于慢波结构的存在，该模式在两个区域内的传播常数不一样。适当调节慢波结构的参数，可使两个区域内传输的扇形TE11模式在金属分割片尾部相位相差180°，这两个扇形TE11模式耦合成为圆波导TE11模式输出，实现模式转换。建立数值模型并进行了模拟，结果表明在工作频率1.8 GHz处转换效率96%，反射率低于0.04，功率容量超过1.7 GW。     

带有锥形增益区14xxnm 量子阱激光器的研制

利用MOCVD生长了14xxnm AlGaInAs/AlInAs/InP应变量子阱外延片.采用带有锥形增益区脊型波导结构和普通条形脊型波导结构在相同的实验条件下制作800 μm腔长激光器管芯，在相同的驱动电流下前者可以获得更高的输出光功率，而且P-Ⅰ曲线线性度较好、饱和电流高. 1200 μm腔长带有锥形增益区脊型波导结构管芯功率达到500 mW，饱和电流3 A以上，峰值波长1460 nm，远场发散角为39°×11°.     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.     

Real-time restoration of rotational blurred image using gradient-loading

The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

Real-time, continuous-wave terahertz imaging by a pyroelectric camera

Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.