The moire topography based on optical logic operation

The optical logic-operated moire,which is proposed on the basis of optical logicoperation,is a new method to obtain specific moire beat pattern.Its advantages lie in the ca-pability to select carrier-free,sharpened fringes with high contrast.The experimental methodand results of the application of the optical logic-operared moire in moire topography are pre-sented in this paper.     

Fast parallel optical digital multiplication

A parallel optical binary multiplication scheme is proposed in which parallel convolution preprocessing is performed using a parallel-input optical outer-product processor together with a one dimensional either space or time integrator. Using a thetamodulation based optical A/D converter and a carry look-ahead adder array, the resulting mixed-binary partial product can be reduced to the final binary multiplication result.     

Fast oscillations in an optical parametric oscillator

We report on the observation of fast oscillations at frequencies of a few MHz in a triply resonant optical parametric oscillator. These oscillations can appear alone, or superimposed on slow oscillations due to thermo-optical instabilities, and display a great variety of waveforms. The analysis of the regimes observed experimentally leads us to conjecture that the mechanism responsible for this instability is not the Hopf bifurcation of the single-mode mean-field model, but that it is based on the interaction of two signal fields oscillating in cavity modes with neighboring frequencies. This interpretation is supported by numerical simulations of the mean-field model with two coupled modes, which reproduce well the behaviors observed experimentally. We also find chaotic solutions of this model, which unveils another possible scenario leading to deterministic chaos in this system.     

Fast wavelength-parallel polarimeter for broadband optical networks

We describe a novel wavelength-parallel polarimeter operating in the light-wave band that measures the complete state of polarization of 256 wavelengths in parallel within 20 ms (software-limited), with the potential for submillisecond operation. By use of fast switching ferroelectric liquid crystals in conjunction with an InGaAs arrayed detector, selection and wavelength-parallel detection of individual polarization components can be achieved within approximately 150 microseconds. This instrument offers unprecedented sensing capability that is relevant to the compensation of polarization-related impairments in high-speed light-wave communications.     

Fast optical recording in dye-doped liquid crystals

Light-induced director reorientation in dye-doped nematic liquid crystals was recently reported to be an efficient method of writing permanent holographic gratings with high sensitivity [Phys. Rev. Lett. 82, 1855 (1999)]. We report the achievement of stable director reorientation in the same materials by means of a single 4-ns pulse of the second harmonic of a Nd:YAG laser. Fast recording of high-resolution holographic gratings (more than 500 lines/mm) can be obtained with an energy density as low as 7x10(-3)J /cm(2) .     

Fast light-emitting silicon-germanium nanostructures for optical interconnects

Epitaxially-grown Si/SiGe quantum dot complexes produce efficient photoluminescence and electroluminescence in the desired spectral range of 1.3–1.6μm. The latest progress in our understanding of the physics of carrier recombination in Si/SiGe nanostructures is reviewed, and a new route toward CMOS compatible light emitters is proposed.     

Fast frictionless expansion of an optical lattice

We investigate fast frictionless expansion of an optical lattice with dynamically variable spacing (accordion lattice). We design an expansion trajectory that yields a final state identical to the initial state up to an irrelevant phase factor. We discuss the effect of additional force and nonlinear interaction on the fast frictionless expansion.     

基于谱域相位分辨光学相干层析的纳米级表面形貌成像

提出了一种基于谱域相位分辨光学相干层析的纳米级表面形貌成像方法,由干涉光谱计算样品相邻两点的相位差,得到样品表面相位差分图,经过积分,重建样品表面形貌的定量分布.当相邻两点相位差的绝对值小于π,不产生相位包裹,避免了目前的干涉法相位解包裹存在的问题,将干涉法相邻两点相位差绝对值的限制条件由目前的π扩大到2π,提高了干涉法表面形貌成像的适用范围.参考面和样品置于同一平台之上,消除环境干扰及系统振动的影响,噪声幅度小于0.3 nm.通过对光学分辨率片及表面粗糙度标准样板的表面形貌成像,对本方法进行了验证,系统的轴向分辨率优于1 nm.     

Fast position measurements with scanning line optical tweezers

Scanning line optical tweezers are a powerful tool for the study of colloidal or biomolecular systems in the low-force regime. We present a fast, high-resolution particle position measurement scheme that extends the capabilities of these instruments into the realm of dynamic measurements. The technique is based on synchronous detection of forward-scattered laser light during a line scan. We demonstrate a position resolution of better than 50 nm for bandwidths of as much as 40 kHz for pairs of microspheres trapped in a flat line potential at center-to-center separations of 1.7-6 microm.     

Fast restoration scheme for MPLS-TP enabled optical multicast

To improve the restoration performance of a multicast service of multi-protocol label switching transport profile （MPLS-TP） enabled optical network,this letter proposes a local-node initiated fast restoration （LNIFR） scheme for MPLS-TP optical multicast service.The proposed scheme allows the local node to establish a segment of fast loopback label switch path by the local node along the upstream of the failed node or link to the nearest downstream node.The fast restoration of optical multicast trees is realized through this part restoration,which focuses on failed node or link.Simulation analysis and results demonstrate that the new scheme outperforms the other schemes in terms of restoration time and success rate.     

Fast optical switching via stimulated Raman adiabatic passage

We demonstrate a new approach to fast optical switching with a technique based on stimulated Raman adiabatic passage in which a laser pulse switches the probe field on and off via another coupling pulse. This new kind of optical switching is not limited by the decay rate of an excited state and can operate in the subnanosecond time domain. The experimental observation in Rb atomic vapor is in good agreement with numerical simulations.     

Fast optical recording in dye-doped polymer-dispersed liquid-crystal films

We describe a fast optical recording material based on a dye-doped polymer-dispersed liquid-crystal film. A holographic grating is written in this film with a single Q -switched Nd:YAG laser pulse that has a duration of ~6 ns . Such a grating is due to the reorientation effect of the liquid-crystal molecules through interaction with the photoinduced adsorption of the doped azo dyes. Experimental results indicate that the grating thus formed is permanent but electrically switchable.     

快速多极边界元法用于扩散光学断层成像研究

在求解扩散光学断层成像中的正向问题时, 目前普遍采用有限元法, 但是随着实际模型规模的增大, 有限元法的计算量问题日益显著, 而边界元法则由于可以降低计算维度使计算量减少而备受关注. 本文以均匀的高散射介质为模型, 研究了将快速多极边界元法用于扩散光学断层成像的正向问题. 快速多极边界元法利用核函数的多极展开, 将常规边界元法中系数矩阵和迭代矢量的乘积项等价为相应四叉树结构的一次递归, 再结合广义最小残量法进行迭代求解. 将计算结果和蒙特卡罗法的模拟结果进行了比较, 表明利用快速多极边界元法的模拟结果和蒙特卡罗法的结果有很好的一致性. 研究结果验证了快速多极边界元法可以用于扩散光学断层成像, 为其大规模和实时成像带来可观的前景. 关键词： 扩散光学断层成像 边界元法 快速多极边界元法     

激光雷达系统快速准直的方法和光学装置

研制了一种能够方便、快速调节激光雷达收发光路准直的光学装置,分析了装置楔角的选取要求、准直误差及其相应的矫正方法。该装置结构简单,主要由两个楔形光学平板组成,通过电机转动两个楔板可使出射光束方向在一定范围内任意改变,该调节范围由楔板的楔角和折射率决定。利用折射定律,严格推导了装置中两个楔形光学平板的旋转角度与出射光束方向之间的关系。提出了将该光学装置插入到激光雷达发射光路,采用螺旋式粗扫、圆形和径向细扫相结合的光束扫描方式实现对激光雷达准直的方法,并给出了系统准直调节过程中的判断准则和具体的准直步骤。     

Fast scanning transmissive delay line for optical coherence tomography

A novel Fourier domain fast scanning optical delay line is proposed in which the walk-off is eliminated by only two passes through a diffraction grating. Working in transmission, the novel delay line is ideal for balanced optical coherence tomography configurations with recirculation of the reference beam. We evaluate theoretically and experimentally its walk-off and dispersion compensation capabilities.     

激光雷达系统快速准直的方法和光学装置

 研制了一种能够方便、快速调节激光雷达收发光路准直的光学装置,分析了装置楔角的选取要求、准直误差及其相应的矫正方法。该装置结构简单,主要由两个楔形光学平板组成,通过电机转动两个楔板可使出射光束方向在一定范围内任意改变,该调节范围由楔板的楔角和折射率决定。利用折射定律,严格推导了装置中两个楔形光学平板的旋转角度与出射光束方向之间的关系。提出了将该光学装置插入到激光雷达发射光路,采用螺旋式粗扫、圆形和径向细扫相结合的光束扫描方式实现对激光雷达准直的方法,并给出了系统准直调节过程中的判断准则和具体的准直步骤。     

Fast frequency modulation optical code division multiple access communication system

An optical fast frequency modulation code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code named functional code is also proposed based on a shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The performance of this system is shown to be better compared with a fast frequency hopping and a spectral amplitude coding systems.     

Fast and accurate reflectivity calculations for shaped core optical fibres

A novel scalar (i.e. paraxial) free space radiation mode method is presented for calculating the normal incidence facet reflectivity of the main guided mode of a step-index optical fibre with generally shaped smooth core. Numerical results are presented and discussed for several cases of the Nth order super-elliptical core shape, including the circular, elliptical, rectangular-type and slab limiting cases.     

Measuring the optical rotation based on the Fast Fourier Transform

Based on the structure of polarizer–Faraday modulator–analyzer, a method of measuring the optical rotation is proposed by using Fast Fourier Transform to analyze the output signal of optical material. The output signal detected by a photodetector comprises two AC components, which angular frequencies are ω and 2ω, respectively. So, the amplitude ratio of different frequency signals can be obtained by using the Fast Fourier Transform. According to the relationship between the amplitude ratio and optical rotation, the optical rotation of material can be detected. Furthermore, the experiment results show that the correlation coefficient between the measured optical rotation and the sugar solution concentration is found to be 0.99979.     

Fast analytical approximation for arbitrary geometries in diffuse optical tomography

Diffuse optical tomography is a novel imaging technique that resolves and quantifies the optical properties of objects buried in turbid media. Typically, numerical solutions of the diffusion equation are employed to construct the tomographic problem when media of complex geometries are investigated. Numerical methods offer implementation simplicity but also significant computation burden, especially when large three-dimensional reconstructions are involved. We present an alternative method of performing tomography of diffuse media of arbitrary geometries by means of an analytical approach, the Kirchhoff approximation. We show that the method is extremely efficient in computation times and consider its potential as a real-time three-dimensional imaging tool.