基于近场光学理论光镊的研究进展

近场光镊是基于近场光学理论建立起来的可以对微粒实现稳定捕获和操作的新技术,相较基于单光束梯度力的传统远场光镊,近场光镊克服了光学分辨率衍射极限和热效应等众多因素的限制,可以实现对纳米量级微小粒子的捕获和操控,在物理学、细胞工程、生物医学等领域备受关注.首先阐述了基于倏逝场近场光镊的模型和捕获的基本原理,详述了棱镜全反射光镊、探针型光镊、纳米孔径光镊、聚焦倏逝场光镊、微纳光纤光镊、以及微谐振腔耦合结构型近场光镊的研究进展.最后,重点介绍了光镊在生物医学领域的应用.     

Particle motion trajectory tracking based on fiber optic tweezers

A biosensor based on single-fiber optical tweezers is proposed, which can detect the motion trajectory of cells based on the stable capture and transmission of silica microspheres as well as biological yeast cells by using a tapered optical fiber as a sensing element. The interference cavity is formed by using the fiber tip and the target particle, the detected interference signal is demodulated using Hilbert transform, and the displacement curve of the particle is plotted to realize the particle motion trajectory tracking. This method provides potential technical support for process monitoring of targeted drug delivery in biomedicine.     

单模光纤微探头式光镊技术

通过对平端面和基于半球形自透镜端面的单模光纤微型探头光镊技术的研究．表明单模光纤微型探头式光镊系统结构简单、捕陷范围大、操纵灵活,可以适应更多的生物细胞和生物分子的光微操作需求．扩大了激光微操纵技术在生命科学中的应用范围。     

干涉式多光镊系统研究

为了定量测量光阱力,采用共面但不同轴的两束激光束产生干涉光场进而构成干涉式光镊系统的方法,分析了两束同向传输激光束以一定角度相干涉从而产生干涉条纹,即2维多光镊的原理,并给出了3维光镊的实验系统。采用分析作用在聚苯乙烯小球上的力的方法,进行了理论分析和实验验证,取得了光阱力分布的数据。结果表明,干涉式光镊可以提供皮牛级横向光阱力,能够实现光捕获,当只考虑光束的束腰半径和光功率两个因素时,实验数据与理论分析吻合得很好。这一结果对光镊技术在生物学、生物医学以及纳米技术等领域的应用是有帮助的。     

用多位置多光程漫透射光谱法分析复杂溶液的Monte Carlo仿真研究

为了进一步提高复杂溶液成分的分析能力和提取更多吸收组分和散射组分的光谱信息,采用多位置多光程漫透射光谱方法对复杂溶液的成分进行了定量分析。实验构建了成分含量不同的100种混合溶液,并采用蒙特卡洛（Monte—Carlo,MC）方法仿真了650nm-1000nm波段的近红外光通过复杂溶液的多位置多光程的透射光谱分布数据。利用偏最小二乘回归的建模方法分别建立了同一光程中心点光谱数据、同一光程多位置光谱数据和多位置多光程光谱数据与复杂溶液中脂肪乳溶液成分含量的模型。通过比较得出,增加径向不同位置的光谱数据和多个光程长的光谱数据,可以提高复杂溶液中物质成分的建模精度和预测能力。     

An all-optical long-distance multi-Gbytes/s bit-parallel WDMsingle-fiber link

An all-optical long-distance (>30 km) bit-parallel wavelength division multiplexed (WDM) single-fiber link with 12 bit-parallel channels having 1 Gbyte/s capacity has been designed. That system functionally resembles an optical fiber ribbon cable, except that all the bits pass on one fiber-optic waveguide. This single-fiber bit parallel wavelength link can be used to extend the (speed x distance) product of emerging cluster computer networks, such as, the MyriNet, SCI, Hippi-6400, ShuffleNet, etc. Here, the detailed design of this link using the commercially available Corning DS (dispersion-shifted) fiber is given. To demonstrate the viability of this link, two WDM channels at wavelengths 1530 and 1545 nm carrying 1 ns pulses on each channel were sent through a single 25.2-km long Corning DS fiber. The walkoff was 200 ps, well within the allowable setup and hold time for the standard ECL logic which is 350 ps for a bit period of 1 ns. This result implies that 30 bit-parallel beams spaced 1 nm apart between 1530-1560 nm, each carrying 1 Gbits/s signal, can be sent through a 25.2-km Corning DS fiber carrying information at a 30 Gb/s rate     

基于Hough变换处理方法的光镊光阱刚度标定

光阱刚度是描述光镊力学特性的一个重要指标,其标定的精确度直接决定了光镊测力的精确度。研究了一种基于Hough变换处理方法的光阱刚度标定方法。首先,介绍了基于均方位移法利用Hough变换求解位移实现刚度标定的基本原理;然后,搭建了光镊系统,进行了可行性分析。测量结果与传统的CCD相关算法进行了比较,当光的放大倍数为120时,Hough变换处理法标定的光阱刚度平均值为1.604±0.02,CCD相关算法标定的光阱刚度平均值为1.781±0.05,两种方法标定的结果基本相同。研究结果表明,Hough变化处理法具有一定的稳定性和可靠性,是标定光阱刚度可选择的方法之一。     

Analysis for the axial force exerted on a micro-particle in the optical vortex

The axial force exerting to a micro-particle in the TEM01* doughnut mode is calculated by using the ray-optic model. The calculated results show that the optical vortex possesses two advantages in trapping the high-index micro-particles com- pared with that of the conventional optical tweezers,of which one is the axial force induced by the optical vortex and is three times as great as that of the optical tweezers under the same power level, and the other is of two equilibrium positions in the optical vortex, which indicates that optical vortex is more suitable in trapping particles. Furthermore, the optical vortex can trap the low-index micro-particles, which can not by the conventional optical tweezers.     

A new single-fiber 10-gb/s optical loopback method using phase Modulation for WDM optical access networks

This paper proposes a new single-fiber 10-Gb/s optical loopback method for wavelength-division-multiplexing (WDM) optical access networks. The proposed method improves the tolerance of backreflection that causes interferometric crosstalk with the loopback method on a single fiber. Furthermore, bit synchronization is used to avoid the problem of wavelength dispersion caused in optical access networks. The authors simulated the available distance, received eye patterns at 10 Gb/s, and confirmed the excellent eye opening. 10-Gb/s back-to-back experiments show that the proposed method provides a 17-dB improvement in backreflection tolerance compared with the direct method. The paper reports the first successful results for 10- and 20-km transmission experiments using a standard single-mode optical fiber. The measured eye patterns agreed well with the simulation results. The paper also shows measured bit-error rates (BERs) equivalent to those of a back-to-back configuration.     

全息光镊在生物学研究中的应用

作为一种非侵入式的高精度微操控和力传感工具,光镊已被广泛应用于生命科学领域的研究。全息光镊利用空间光调制器调控光场,可以灵活地产生任意排布的光阱阵列,具有比传统单光镊更高的灵活性,目前已在生物医学领域展现出巨大的应用价值。本文综述了全息光镊的基本原理、全息图算法,以及全息光镊在生物学领域的研究进展,希望可以为全息光镊在生物学中的应用研究提供一定的参考。     

真空光镊系统及其在精密测量中的研究进展

光镊具有非接触、低损伤和适用范围广等特性,被广泛应用于生命科学、纳米科技等领域。光镊系统通过调制束缚光场操控机械振子的运动,借助光动量和角动量的检测获取振子的运动状态,以实现对振子物理参量的精密测量。与传统液体光镊系统不同,真空光镊系统中的机械振子可获得与外界环境近乎完全隔离的状态,具有超高灵敏度的探测能力,是精密测量和基础物理研究的理想平台。首先介绍了真空光镊系统相关的基础理论,然后介绍了真空光镊系统的实验配置方案及其在精密测量中的典型应用,最后总结了真空光镊系统的发展现状,并给出了未来的发展建议。     

基于有限远光学系统的光镊设计和调整

光镊可以非接触、无损伤地操纵尺度位于数纳米到数十微米之间的生物细胞、亚细胞、生物大分子以及胶体粒子,已经成为生命科学和胶体化学领域不可缺少的研究工具。根据几何光学,对基于有限远光学系统显微镜的光镊光路进行了分析计算。这类系统由捕获光源、准直透镜、倒置生物显微镜、大数值孔径物镜、成像系统和CCD相机组成,可以在保持物镜后瞳充满度的情况下调整阱位和刚度,具有捕获力大、被捕获的粒子成像清晰等优点,可以很好地满足科研和教学需求。     

Controllable Cellular Micromotors Based on Optical Tweezers

Micromotors hold exciting prospects in biomedical applications but still face a great challenge. To date, there have been few reports of micromotors with high safety, flexible controllability, and full biocompatibility. Here, a multifunctional method based on an optical tweezer system is presented to realize controllable cellular micromotors. The method not only satisfies all of the above criteria but is also independent of the cell types and materials. Optical tweezers are used to generate a dynamic scanning optical trap along a given circular trajectory, which can trap and drive a microparticle or a single cell to move along the trajectory and thus generate a microvortex. Cells within the microvortex will be controllably rotated under an action of shear stress or torque and their rotation rate and direction can be controlled by changing the scanning frequency and direction of the dynamic optical trap. The proposed method is effective for both immotile target cells and swimming target cells. Additionally, it is further applied to realize synchronous translation and rotation of cellular micromotors and to assemble controllable and fully biocompatible cellular micromotor assays. The proposed method is believed to have potential applications in targeted drug delivery, biological microenvironment monitoring and sensing, and biomedical treatment.     

光镊--研究分散体系的新手段

光镊能够稳定捕获微米、亚微米量级粒子的特性，使得人们可以在粒子层次上直接研究它们之间的相互作用，从而为深入认识分散体系的各种宏观性质的微观机制开拓了有效的研究途径。本文对光镊出现以后，它在分散体系研究中的一些重要进展作了综合评述，并对光镊在该领域的应用进行了展望。     

T矩阵在光阱分析中的应用

光镊技术被广泛应用于许多生物领域。光镊本身结构简单,用单光束就可以捕获单个粒子,但对光阱力的精确计算却存在一定的难度。可以用一些近似的方法如几何光学或瑞利假设分析光阱力,但这些方法仅能在特定限制条件下适用。文中把电磁散射理论作为一种通用的方法来解决光阱力的计算问题。论述了如何使用T矩阵方法进行光阱力计算。计算结果为实验系统参量的选择提供了理论依据。     

可调谐单纵模多波长光纤激光器的研究

为了实现对台阶高度和绝对距离等物理量的高精度干涉测量,采用在一个光纤激光器中构建多个激光谐振腔的方法,构建了能同时发出多波长激光的光纤激光器。每个激光谐振腔都利用掺铒光纤作为增益介质,利用光纤光栅作为波长选择元件,改变光纤光栅的布喇格波长,即可改变对应谐振腔的激光波长。各个激光谐振腔独立但部分重叠,在重叠区域利用光纤耦合器构成复合子腔,使每个激光谐振腔都是复合激光谐振腔,从而使每个激光谐振腔都发出单纵模激光。结果表明,该光纤激光器能同时发出功率和频率都稳定的多波长激光,且每个波长都是单纵模激光;在4h内,每个波长的波长稳定性优于0.01nm。该设计对可调谐单纵模多波长光纤激光器的研究是有帮助的。     

光阱刚度与实验条件的依赖关系

对微小力的测量是光镊系统的重要功能。主要研究了进行微小力测量时所需的重要参数——光阱刚度与实验条件的依赖关系。在以He-Ne激光器为光源的光镊系统中，得到了光阱刚度随着阱位距离样品池底面高度的提升而减小，随着被捕获小球直径的增加而减小，以及光阱刚度与激光功率具有线性的依赖关系等经验规律，并作了定性的讨论。最后给出了该系统所能达到的测力精度和测力范围。     

A new method for fiber chromatic dispersion measurement with microwave interference effect

The chromatic dispersion (CD) is a key parameter for optical fibers. Based on the microwave interference effect, a new method for CD measurement of optical fibers is proposed. The radio frequency (RF) signals carried by two light-waves with different wavelengths transmit through the dispersive optical fiber under test. After photo-detector they interfere with each other due to the different phase shifts induced by the CD of fiber. The CD can be obtained by monitoring the changing interference RF power with scanning the wavelength of tunable laser source. The CD values of single mode fiber and dispersion compensating fiber are measured within the wavelength range from 1525 to 1605 nm. The common phase shift method is used to measure the CDs of the two types of fiber, which demonstrates the feasibility and veracity of the proposed method.     

激光微束场对微粒子辐射力的作用

本文分析了激光微束对微粒子的辐射力的作用，在建立的激光微束系统上，用光镊捕获了空心电介小球和酵母细胞，验证了光镊的光动力学效应，用光镊实现了微粒子的捕获、移动、翻转等一系列操作，甚至可以同时捕获许多微粒子，从理论和实践上验证了激光微束对微粒子的动力学作用。     

Determination of interface trap capture cross sections usingthree-level charge pumping

A modified three-voltage-level charge pumping (CP) technique is described for measuring interface trap parameters in MOSFETs. Charge pumping (CP) is a technique for studying traps at the Si-SiO₂ interface in MOS transistors. In the CP technique, a pulse is applied to the gate of the MOSFET which alternately fills the traps with electrons and holes, thereby causing a recombination current I_cp to flow in the substrate. With this technique, interface trap capture cross sections for both electrons and holes may be determined as a function of trap energy in a single device. It is demonstrated that a modified three-level charge pumping method may be used to determine not only interface trap densities but also to capture cross sections as a function of trap energy. The trap parameters are obtained for both electrons and holes using a single MOSFET