实时测量表面形貌的正弦相位调制半导体干涉仪

提出一种实时测量表面形貌的正弦相位调制半导体激光干涉仪。利用实时相位检测电路，从正弦相位调制干涉信号中解出被测量物体表面形貌的相位。在实验中，测量了楔形光学平板的表面形貌，对表面形貌上的60

一种使用双棱镜的动态小角度测量方法

提出一种基于正切关系和相位调制技术的动态小角度测量方法。使用双棱镜组成干涉测量臂引导两束平行光至分束棱镜处干涉,通过提取携带被测信息的干涉信号的相位实现动态的小角度测量。由于采用位置探测器(PSD)对测量臂中两平行光束的间距进行测量,简化了测量方程,消除了装置中双棱镜必须对称放置的要求。通过正弦地改变半导体激光器的注入电流在时域内实现对干涉信号的相位调制,形成准外差干涉测量模式,提高了光程差的测量精度。实验验证了该方法的可行性,并讨论了影响小角度测量精度的误差因素。研究结果表明,基于该方法的动态小角度的重

基于掺镧锆钛酸铅电光材料的光学相控阵光束扫描器

基于掺镧锆钛酸铅(PLZT)电光陶瓷材料的光学特性,提出了一种具有上下电极结构的光学相控阵高速光束扫描器。在理论上,分析了具有这种结构的光学相控阵的光束电光偏转特性和机制;在实验上,分析了掺镧锆钛酸铅材料的相位调制特性和损耗特性,制作了相关的光学相控阵器件,并构建了相应的测试系统,获得了光束在空间的角度偏转,与理论分析结果相符。

Invertible dark-center diffraction of the metal film induced by femtosecond laser

We found reversible dark-center diffraction of the transmitted probe beam passing through the chromium film. which is induced by the pump femtosecond laser. The dark-center diffraction of I he transmitted probe beam appears and disappears with and without the pump beam. A view of diffractive optics with binary phase plate is put forward, which explains the reversible dark-center diffractive optical phenomenon. The pre-ablated hole on the metal film can be regarded as a uniform light filed without phase modulation, the Surrounding Circular part around the pre-ablated hole can be regarded as "phase modulated". Therefore, this diffraction optic view might be helpful for us to understand the phase change of the metal film introduced by the femtosecond laser pulse. (C) 2008 Elsevier B.V, All rights reserved.

Compensation for self-focusing by use of cascade quadratic nonlinearity

We demonstrate theoretically and experimentally compensation for positive Kerr phase shifts with negative phases generated by cascade quadratic processes. Experiments show correction of small-scale self-focusing and whole-beam self-focusing in the spatial domain and self-phase modulation in the temporal domain. (C) 2001 Optical Society of America.

利用消衍射透镜列阵及光谱色散平滑实现焦斑均匀辐照

提出将空间域的透镜列阵法和时间域的光谱色散平滑法结合起来实现靶面的均匀辐照．消衍射型透镜列阵能获得边缘陡峭且顶部较平坦的准近场焦斑，光谱色散平滑则能有效地抹平焦斑内部由多光束干涉引起的细密条纹．数值结果显示，通过该方案能获得均匀性较好的焦斑．进一步分析了光谱色散平滑单元中位相调制和光栅的参数对辐照均匀性的影响，发现参数的选取要在焦斑均匀性和能量利用率之间取得合理平衡，以在整体上获得最佳的均匀辐照效果．

调Q及连续掺Yb光纤激光器中的自锁模研究

在用半导体激光器抽运的单包层掺Yb调Q光纤激光器中观察到了清晰稳定的自锁模脉冲序列。脉冲包络形状为调Q脉冲。每个锁模脉冲的幅值由其在调Q脉冲中的相应位置决定。经过分析，认为自相位调制是调Q光纤激光器中产生锁模的主要原因。自相位调制的存在使得光脉冲的频谱被展宽，当这种展宽和腔的模式间隔相差不多时，腔内的模式便能相互作用，直到它们之间产生一个固定的相位关系。也即形成锁模。在此基础上。去掉声光晶体，并用两个光栅作为腔镜，实现了全光纤法布里-珀罗(F-P)腔锁模光纤激光器。改变腔结构，分别采用光栅和光纤反射圈作为

基于光纤环形镜的全光脉冲整形器

提出了一种基于光纤环形镜的全光脉冲整形器。该全光脉冲整形器利用波分复用器将控制光脉冲引入光纤环形镜中，控制光脉冲由于交叉相位调制在信号光上产生了非线性附加相移。信号光在耦合器中发生干涉，经过整形的信号光脉冲从脉冲整形器的出射端出射，信号脉冲的波形由非线性附加相移的波形决定。实验中．利用对控制脉冲光谱整形和啁啾展宽的方法来对控制脉冲进行时间脉冲的整形，该全光脉冲整形器实现了对单纵模激光的脉冲整形，同时实现了飞秒脉冲和单纵模整形脉冲的精确同步。在理论上数值计算了该全光脉冲整形器的输出特性，理论计算结果和实验结

谱色散平滑与透镜列阵联用实现均匀照明

为满足激光惯性约束聚变中靶面激光辐照不均匀性低于5%的要求, 在目前使用透镜列阵基础上, 提出了谱色散平滑与透镜列阵联用方案, 对其进行数值计算并分析其平滑效果和应用可行性。结果表明:焦斑的不均匀性从单独使用透镜列阵时的14%降低到与谱色散平滑结合后的3%;对焦斑点功率谱的分析表明谱色散平滑通过抑制焦斑中高频的频谱强度达到平滑效果。该方案可以进一步提高焦斑平滑效果, 计算结果对实际应用有着重要的参考意义。

四区域法消除偏振棱镜缺陷对波片相位延迟测量的影响

在起偏器待测波片检偏器系统基础上提出一种四区域测量波片相位延迟量的方法。调整待测波片和检偏器的方位角,获得相应的四组光强值,通过线性运算得到待测波片的相位延迟量,完全消除了起偏器和检偏器不完全消光带来的误差。由于测量系统中不存在标准波片或其他相位调制元件,允许测量波长仅受偏振棱镜和探测器的限制,因此四区域法可适用于很大波长范围内的波片测量。以λ/4波片为例,理论分析了测量系统利用四区域测量法后的仪器误差为σ≤±3.49065×10-3rad(约0.2°),精度比原算法提高约1个数量级。实验验证了四区域法能有效提高系统精度。

Simulador MATLAB para Sistemas Ópticos WDM Amplificados.

Neste trabalho é apresentado um simulador MATLAB para sistemas ópticos WDM amplificados baseado na solução das equações não lineares de Schrödinger acopladas, pelo método de Fourier de passo alternado. Este simulador permite o estudo da propagação de pulsos em fibras ópticas, considerando dispersão cromática, efeitos não lineares como automodulação de fase e modulação de fase cruzada e atenuação, prevendo também o emprego de amplificadores ópticos a fibra dopada com Érbio (EDFAs). Através de simulações numéricas, foi explorada a técnica de otimização do posicionamento de um EDFA ao longo de um enlace óptico, sem repetidores, que objetiva a redução dos custos de implantação de sistemas ópticos, seja pela diminuição da potência do transmissor ou pela relaxação da exigência de sensibilidade do receptor. Além disto, pode favorecer um aumento na capacidade do sistema, através do aumento do alcance ou da taxa de transmissão. A concordância dos resultados obtidos com os disponíveis na literatura confirmam a validade da técnica, bem como a versatilidade e robustez do simulador desenvolvido.

Wavelength conversion using semiconductor optical amplifiers

This paper reports a detailed theoretical study of the dynamics of wavelength conversion using cross-gain and cross-phase modulation in semiconductor optical amplifiers (SOA's) involving a large signal, multisection rate equation model. Using this model, recently reported experimental results have been correctly predicted and the effects of electrical and optical pumping on the conversion speed, modulation index, and phase variation of the converted signal have been considered. The model predicts, in agreement with experimental data, that recovery rates as low as 12 ps are possible if signal and pump powers in excess of 14 dBm are used. It also indicates that conversion speeds up to 40 Gb/s may be achieved with less than 3 dB dynamic penalty. The employment of cross-phase modulation increases the speed allowing, for example, an improvement to 60 Gb/s with an excess loss penalty less than 1 dB.

Electro-optic characteristics of a transparent nanophotonic device based on carbon nanotubes and liquid crystals.

We present electro-optic characteristics of a transparent nanophotonic device fabricated on quartz substrate based on multiwall carbon nanotubes and nematic liquid crystals (LCs). The nanotube electrodes spawn a Gaussian electric field to three dimensionally address the LC molecules. The electro-optic characteristics of the device were investigated to optimize the device performance and it was found that lower driving voltages were suitable for microlens array and phase modulation applications, while higher driving voltages with a holding voltage can be used for display-related applications.

Ballistic Single-Electron Quputer

We propose a new solid state implementation of a quantum computer (quputer) using ballistic single electrons as flying qubits in 1D nanowires. We use a single electron pump (SEP) to prepare the initial state and a single electron transistor (SET) to measure the final state. Single qubit gates are implemented using quantum dots as phase shifters and electron waveguide couplers as beam splitters. A Coulomb coupler acts as a 2-qubit gate, using a mutual phase modulation effect. Since the electron phase coherence length in GaAs/AlGaAs heterostructures is of the order of 30$\mu$m, several gates (tens) can be implemented before the system decoheres.

Bias-dependent recovery time of all-optical resonant nonlinearity in InGaAsP/InGaAsP MQW waveguide

We have investigated a resonant refractive nonlinearity in a semiconductor waveguide by measuring intensity dependent phase shifts and bias-dependent recovery times. The measurements were performed on an optimized 750-μm-long AR coated buried heterostructure MQW p-i-n waveguide with a bandedge at 1.48 μm. Figure 1 shows the experimental arrangement. The mode-locked color center laser was tuned to 50 meV beyond the bandedge and 8 ps pulses with peak incident power up to 57 W were coupled into the waveguide. Some residual bandtail absorption remains at this wavelength and this is sufficient to cause carriers to be photogenerated and these give rise to a refractive nonlinearity, predominantly by plasma and bandfilling effects. A Fabry-Perot interferometer is used to measure the spectrum of the light which exits the waveguide. The nonlinearity within the guide causes self phase modulation (SPM) of the light and a study of the spectrum allows information to be recovered on the magnitude and recovery time of the nonlinear phase shift with a reasonable degree of accuracy. SPM spectra were recorded for a variety of pulse energies coupled into he unbiased waveguide. Figure 2 shows the resultant phase shift measured from the SPM spectra as a function of pulse energy. The relationship is a linear one, indicating that no saturation of the nonlinearity occurs for coupled pulse energies up to 230 pJ. A π phase shift, the minimum necessary for an all-optical switch, is obtained for a coupled pulse energy of 57 pJ while the maximum phase shift, 4 π, was measured for 230 pJ. The SPM spectra were highly asymmetric with pulse energy shifted to higher frequencies. Such spectra are characteristic of a slow, negative nonlinearity. This relatively slow speed is expected for the unbiased guide as the recovery time will be of the order of the recombination time of the photogenerated electrons, about 1 ns for InGaAsP material. In order to reduce the recovery time of the nonlinearity, it is necessary to remove the photogenerated carriers from the waveguide by a process other than recombination. One such technique is to apply a reverse bias to the waveguide in order to sweep the carriers out. Figure 3 shows the effect on the recovery time of the nonlinearity of applying reverse bias to the waveguide for 230 pJ coupled power. The recovery time was reduced from one much longer than the length of the pulse, estimated to be about 1 ns, at zero bias to 18 ± 3 ps for a bias voltage greater than -4 V. This compares with a value of 24 ps obtained in a bulk waveguide.