基于自回归模型的光阱中粒子运动模拟

通过分析光阱中颗粒位移信号特性, 建立描述粒子受限布朗运动过程的自回归模型, 进而提出了一种基于自回归模型的光阱中颗粒运动信号模拟的新方法. 对半径为1 μm的粒子处于光阱刚度分别为10, 20, 50 pN/μm 光阱时的位移信号进行了模拟, 得到的模拟位移信号的自相关函数与理论值相一致. 为了进一步阐明自回归模型的有效性, 在相同光阱参数下, 分别采用自回归模型与蒙特卡罗方法模拟光阱中微粒的位移信号, 采用功率谱法分别对两种模拟方法所得的微粒位移标定光阱刚度, 结果表明自回归模型方法能够取得和蒙特卡洛法相同的精度. 因此, 本文为分析光阱中粒子的随机运动提出了一种新的模拟方法, 可以用来对光阱中的噪声及特性进行分析. 关键词： 光阱 布朗运动 信号模拟 自回归模型     

光阱中布朗粒子动力学分析

通过对光阱中的布朗粒子进行动力学方程求解,由解的结果分析得到观测系统的性能要求．结果表明：光阱中布朗颗粒服从Boltzmann分布;对其运动的观测需要纳米量级的空间分辨率和毫秒量级的时间分辨率．     

金纳米棒的单光束光操纵及其散射谱的测量

利用波长为800nm的单光束飞秒激光对水溶液中的金纳米棒颗粒进行了稳定地二维光捕获.通过测量金纳米棒的散射谱研究了光阱中金纳米棒之间的耦合相互作用.比较光阱中只有单个金纳米棒被捕获和两个金纳米棒同时被捕获时的散射谱.结果表明,当两个金纳米棒同时被光阱捕获时,金纳米棒之间相互排斥,存在一定的间隔,该间隔使得两个金纳米棒之间没有发生表面等离子耦合相互作用.该实验结果为金纳米棒的光操纵及其在生物分子探测等领域的研究提供技术指导及实验参考.     

用空间光调制器产生三维光阱阵列

本文提出了用液晶空间光调制器制作复合相位光栅、产生三维光阱阵列的新方案．在本方案中,首先将一维矩形光栅转变为能够产生纵向光阱阵列的环形光栅,再把环形光栅和二维矩形光栅组合成复合光栅．根据现有空间光调制器的技术参数,模拟仿真设计了产生5×5×5光阱阵列的光栅,以普通功率的高斯光波为输入光,正透镜聚焦衍射光,计算输出光强分布,结果表明：在透镜焦点附近获得具有很高峰值光强和光强梯度的三维光阱阵列,囚禁冷原子的光学偶极势达到mK量级,对原子的作用力远大于原子的重力．用大功率激光作为输入光波时,产生的光阱阵列也能用于囚禁Stark减速后的冷分子．     

基于卡尔曼滤波的真空光阱悬浮微球位移探测

在光阱实际测量中,过程噪声以及光电测量噪声严重影响微球位移实时探测的灵敏度,针对这一问题,提出基于卡尔曼滤波的方法对微球位移进行探测.将光阱中微球运动的谐振子模型改写成卡尔曼滤波的状态转移矩阵形式,获得具有高灵敏度和高信噪比的微球位移信号.仿真结果表明:1 MHz的采样频率下,101kPa气压下滤波后的真空光阱微球位移的探测均方根误差从1nm降到0.27nm.实验结果表明,在293K、101kPa气压下对实测的微球位移信号进行滤波,探测均方根误差从2.8nm降到1.1nm;其他参数不变,在1Pa气压下均方根误差从5.2nm降到2.1nm.该方法可应用于高真空下光阱微球质心运动的激光冷却反馈方案.     

两种非球形细胞光镊阱力标定方法的比较

玻尔兹曼统计法和均方位移法是两种可用于对非球型生物细胞在简谐光势阱中光阱力的标定方法. 用数字实验对这两种标定方法进行了比较, 结果表明： 与均方位移法相比,玻尔兹曼统计法不仅适用于各向异性非球性细胞,也适用于非简谐、非对称光势阱中任意形状的生物细胞光阱力的标定,结论与已有直接实验相符.     

光纤探针型近场光镊光阱力特性研究

基于动量守恒原理,结合麦克斯韦应力张量和三维时域有限差分方法,建立了近场空间内激光光镊对纳米微粒的光阱力计算模型.分析了光纤探针型近场光镊的近场分布以及操作纳米微粒时各轴向光阱力的分布情况,并探讨了光纤探针尖端的捕获尺寸、捕获位置和操作稳定性.结果表明:微粒应处于光纤探针针尖的近场空间内才可实现稳定可靠的纳米操作,不同尺寸的微粒具有不同的捕获效果,且随初始位置的不同微粒的捕获位置亦不同.计算结果为激光近场光镊纳米操作装置的设计和制造提供了理论基础.     

光纤探针型近场光镊光阱力特性研究

基于动量守恒原理,结合麦克斯韦应力张量和三维时域有限差分方法,建立了近场空间内激光光镊对纳米微粒的光阱力计算模型.分析了光纤探针型近场光镊的近场分布以及操作纳米微粒时各轴向光阱力的分布情况,并探讨了光纤探针尖端的捕获尺寸、捕获位置和操作稳定性.结果表明:微粒应处于光纤探针针尖的近场空间内才可实现稳定可靠的纳米操作,不同...     

以慢原子束方式进行原子转移的双磁光阱系统

建立了一套用于玻色-爱因斯坦凝聚实验的铷原子双磁光阱装置.从低速强源中获得慢原子束，向超高真空磁光阱进行原子转移.低速强源磁光阱与超高真空磁光阱之间可维持3个量级的压强差,超高真空磁光阱的真空度最高可达1×10^-9 Pa. 慢原子束的束流通量达1×10⁹/s. 约4×10⁸个⁸⁷Rb原子被装载到超高真空磁光阱中.还讨论了两种典型情况下磁光阱中装载的最大原子数.     

中性原子的表面双磁光阱及其应用

提出了一种新的采用载流导线的表面双磁光阱(MOT)方案(即双U型导线磁光阱方案)。通过改变中间U型导线中的电流大小,即可将一个双磁阱连续地合并为一个单磁阱,反之亦然。详细计算和分析了上述双U型载流导线磁光阱方案的磁场及其梯度的空间分布,研究发现当导线中的电流为600 A,z方向均匀偏置磁感应强度为-4.0×10-3 T时,双U型导线方案产生的两个磁阱中心的磁场梯度约为1.5×10-3~2.5×10-3 T/cm,结合通常制备磁光阱时所用的三维粘胶(Molasses)光束即可在基底表面附近形成一双磁光阱。理论分析表明在弱光近似下,每个磁光阱中所能俘获的85Rb原子数约为106 量级,相应的磁光阱温度约为270μK。由于双磁光阱可以独立制备,所以双U型导线方案特别适用于制备双样品磁光阱,并用于研究双原子样品的冷碰撞性质。     

Methods of calibration to optical trapping force upon non-spherical cells

The dynamical equation of a trapping cell is solved to find calibration methods for the trapping force, and two methods are compared by synthetic experiment data. Results indicate that: Boltzmann distribution method (BDM) is available for the force calibration of non-spherical or anisotropic cells in arbitrary trap potential; the mean square displacement method (MSDM) is available only for a symmetric harmonic optical trap. The spatial resolution requirement of the calibration system is about a nanometer. The results agree with the reported experiments.     

基于F-P腔法的纳米精度非线性误差校准系统研究

为了研究可用于纳米、亚纳米精度的非线性误差校准系统,采用差拍F-P干涉法,在中国计量科学研究院研制的差拍F-P干涉仪基础上,设计并制作了适用于该系统的密封干涉光路的真空系统。通过与电容式测微仪的比对实验,证明了系统的抗干扰能力得到了改善,在大于半波长的测量范围内,系统的非线性度优于3.86nm。     

Experimental measurement and analysis of the optical trapping force acting on a yeast cell with a lensed optical fiber probe

Based on an optical trapping system with a single-lensed fiber probe inserted at an angle, the sub-picoNewton trapping force acting on a yeast cell as a function of the displacement is measured experimentally by the static and dynamic methods, respectively, whose measurement processes are presented in detail. The measured maximum trapping efficiency is 0.07 in our experiment, which is an order of magnitude lower than that of the optical tweezers. The characteristics of the trapping force in the various horizontal directions are discussed. Finally, the analysis of the measurement error shows the factors and their magnitude which cause error, and offers a way to reduce the error in future.     

用于瞬态力学量测试的光学传感器设计及应用

基于光纤耦合反射式光束偏转法,提出了一种可用于瞬态力学量测试的光学传感器,并详细给出了该测试机理.采用该传感器,在靶材对心处实时检测到由于空泡在固体靶材附近溃灭时射流冲击力引起的靶材瞬态微小变形.通过对该传感器定标可以进一步得到作用冲击力大小.这种传感器的应用将有助于了解激光诱导产生空泡射流运动特性及其对靶材的损伤机制.     

Two-wavelength sinusoidal phase-modulating interferometer for nanometer accuracy measurement

A two-wavelength sinusoidal phase-modulating(SPM) laser diode(LD) interferometer for nanometer accuracy measurement is proposed.To eliminate the error caused by the intensity modulation,the SPM depth of the interference signal is chosen appropriately by varying the amplitude of the modulation current periodically. Then,the refine theory is induced to the measurement,and the two-wavelength interferometer (TWI) is combined with the single-wavelength LD interferometric technique to realize static displacement measurement with nanometer accuracy.Experimental results indicate that a static displacement measurement accuracy of 5 nm can be achieved over a range of 200μm.     

Optical properties of (nanometer MCM-41)-(malachite green) composite materials

Nanosized materials loaded with organic dyes are of interest with respect to novel optical applications. The optical properties of malachite green (MG) in MCM-41 are considerably influenced by the limited nanoporous channels of nanometer MCM-41. Nanometer MCM-41 was synthesized by tetraethyl orthosilicate (TEOS) as the source of silica and cetyltrimethylammonium bromide (CTMAB) as the template. The liquid-phase grafting method has been employed for incorporation of the malachite green molecules into the channels of nanometer MCM-41. A comparative study has been carried out on the adsorption of the malachite green into modified MCM-41 and unmodified MCM-41. The modified MCM-41 was synthesized using a silylation reagent, trimethychlorosilane (TMSCl), which functionalized the surface of nanometer MCM-41 for proper host-guest interaction. The prepared (nanometer MCM-41)-MG samples have been studied by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, low-temperature nitrogen adsorption-desorption technique at 77 K, Raman spectra and luminescence studies. In the prepared (nanometer MCM-41)-MG composite materials, the frameworks of the host molecular sieve were kept intact and the MG located inside the pores of MCM-41. Compared with the MG, it is found that the prepared composite materials perform a considerable luminescence. The excitation and emission spectra of MG in both modified MCM-41 and unmodified MCM-41 were examined to explore the structural effects on the optical properties of MG. The results of luminescence spectra indicated that the MG molecules existed in monomer form within MCM-41. However, the luminescent intensity of MG incorporated in the modified MCM-41 are higher than that of MG encapsulated in unmodified MCM-41, which may be due to the anchored methyl groups on the channels of the nanometer MCM-41 and the strong host-guest interactions. The steric effect from the pore size of the host materials is significant. Raman spectra firmly demonstrated the stable form obtained after the MG incorporation into the nanometer MCM-41. Therefore, nanometer MCM-41 appears to have a good potential for its use as a support for dyes and the (nanometer MCM-41)-MG composite materials may give a wide optical application.     

纳米光镊技术发展与应用的研究

阐述了纳米光镊技术的特点，它将操作和探测精度从微米提高到纳米。归纳和总结了纳米光镊技术最新方面的研究进展，叙述了一些先进组合技术在改进光镊装置构造、操作精度以及校准方面的应用，并在此基础上提出了一些构想和建议。     

Effects of vibrations of a spatial filter in signal detection by matched filtering

In the present paper, the effect of transverse and longitudinal vibrations of a spatial filter in signal detection by optical matched filtering has been investigated. It has been assumed that the noise spectral density is uniform. Degradation in the performance of such an optical information processing system has been illustrated graphically. It is noticed that the effect of transverse vibrations is more severe than that of longitudinal vibrations. Results have also been compared with those obtained by Van der Lugt for the case of static displacement of a spatial filter.     

Optical heterodyne grating shearing interferometry for long-range positioning applications

We develop a displacement measurement and positioning system with nanometer resolution over the millimeter traveling range. The method is based on a heterodyne grating shearing interferometry, a homemade lock-in amplifier and a servo control loop for displacement sensing and positioning. The quasi-common optical path configuration of our system provides better immunity against environmental disturbances. The experimental results demonstrate that our system can measure small and long displacement with nanometric resolution. The device achieves a positioning resolution of 2.3 nm over a traveling range of 20 mm.