微粒在涡旋光场高阶贝赛尔光束中的受力分析

根据涡旋光场高阶贝赛尔光束表达式,推导出了微粒在此光束中所受轴向力的表达式并进行了计算.分别研究了在贝塞尔光束中,高折射率微粒与低折射率微粒所受轴向力与粒子半径、折射率、光束波长、束腰半径之间的关系.数值结果表明该光束不仅可以捕获高折射率微粒,也可以捕获低折射率微粒.     

对米氏粒子轴向光阱力与横向光阱力的测量研究

基于几何光学原理,在强聚焦激光光场中,以射线光学计算模型为基础,对几何尺寸远大于光波长的米氏球状粒子所受的轴向与横向光阱力进行计算.并在给定参数条件下,进行数值仿真,讨论各主要参数与光阱力的关系.     

光镊轴向力与吸收系数等参数的关系研究

以射线光学模型为基础．对微粒直径远大于激光微束的米氏粒子在考虑对光的吸收时轴向力与光源参数的关系进行了计算，计算结果给出了轴向力与微粒的吸收系数、波长、激光功率等参数的关系，为实验中参数的选择提供了依据．     

微粒在会聚高斯光束中的受力分析

以射线光学模型为基础,对会聚高斯激光束中微粒所受轴向力进行了计算.数值计算的结果表明,束腰越小捕获越稳定;相对折射率必须大于1并存在一个最佳相对折射率;激光波长、粒子半径以及激光功率也对捕获力有重要影响.数值计算和分析为搭建光镊仪器选取系统参数提供必要的理论依据.     

高质量超短光脉冲的产生与表征

分析半高全宽光脉冲表征体系的不足,提出用以表征光脉冲时域和频域特性的方均根光脉冲表征体系.采用空心波导对飞秒激光腔内的光束进行调制,并分别用2种光脉冲表征体系表征了实验中产生的lO-15s光脉冲,得到了高质量的飞秒激光脉冲.结果表明,方均根光脉冲表征体系能够更加准确地表征飞秒光脉冲.     

飞秒光镊技术的研究进展

因在光镊及超短激光脉冲方面开创性的工作,A. Ashkin、G. Mourou和D. Strickland分享了2018年度诺贝尔物理学奖。本文概述了将超短激光脉冲和光镊相结合的飞秒光镊技术的研究进展。简要介绍了飞秒光镊技术的基本原理,重点介绍了飞秒光镊技术中的非线性光学效应和光学捕获动力学行为,最后讨论了飞秒光镊技术中的调控手段,展望了飞秒光镊技术的发展前景。     

熔凝石英中异常色散条件下飞秒脉冲激光辐射的丝状形成特征的研究

本文描述了在800—2300纳米变化波长范围内溶凝石英的飞秒脉冲激光辐射丝状形成的研究结果。指出了在很高时间与空间定位的光场中异常群色散速度条件下沿着细丝连续“光弹头”的产生。建立了光弹头传播的变化过程中使绝缘反斯托克斯翅膀的产生与超光谱连续统一体关系。     

飞秒激光场中甲醇产物离子的角分布

利用直流切片离子成像技术结合飞行时间质谱技术,我们研究了甲醇(CH_3OH)分子在800 nm飞秒激光场中的多光子解离和库仑爆炸过程.获得了甲醇分子在光场中的飞行时间质谱和产物离子的切片影像,分析得到了不同库仑爆炸通道碎片离子的动能分布和角度分布.本文对比分析了C-O键断裂产生H_2O~+的H转移通道和产生OH~+的非H转移通道的角分布,计算了不同激光强度下两个通道的各向异性参数α_2和(cos~2θ),并根据产物离子角度分布与激光强度和离子价态的关系,揭示了甲醇分子在飞秒光场中的准直机制为动力学准直.     

飞秒脉冲通过体全息光栅弱耦合衍射特性分析

由Kogelnik单色衍射效率公式推导出了飞秒激光脉冲光在弱耦合情况下的衍射效率频谱,分析了飞秒激光脉冲通过体全息光栅弱耦合衍射特性。衍射光的频谱分布与读出飞秒脉冲的宽度Δτ、体全息光栅的周期Λ,厚度d以及晶体折射率调制度Δn0有密切关系。通过控制光栅的写入和读出过程,选择适当的参量数值,可以得到不同衍射强度和不同频率成分的衍射光。对于研究飞秒脉冲光通过光折变光栅传播特性以及飞秒超短脉冲用于光学信息处理有应用意义。     

飞秒激光在半透明物质中的微爆破及应用

飞秒激光可以在玻璃内部加工出各种微小器件,比如光波导、光栅光耦合器等,也可以用在深板层内皮角膜移植手术中．因此,研究飞秒激光在半透明物质中的微爆,对医学应用领域具有重要的参考价值．文章介绍并探讨了飞秒激光在生物医学方面的应用及发展动态．     

Simultaneous micromanipulation in multiple planes using a self-reconstructing light beam

Optical tweezers are commonly used for manipulating microscopic particles, with applications in cell manipulation, colloid research, manipulation of micromachines and studies of the properties of light beams. Such tweezers work by the transfer of momentum from a tightly focused laser to the particle, which refracts and scatters the light and distorts the profile of the beam. The forces produced by this process cause the particle to be trapped near the beam focus. Conventional tweezers use gaussian light beams, which cannot trap particles in multiple locations more than a few micrometres apart in the axial direction, because of beam distortion by the particle and subsequent strong divergence from the focal plane. Bessel beams, however, do not diverge and, furthermore, if part of the beam is obstructed or distorted the beam reconstructs itself after a characteristic propagation distance. Here we show how this reconstructive property may be utilized within optical tweezers to trap particles in multiple, spatially separated sample cells with a single beam. Owing to the diffractionless nature of the Bessel beam, secondary trapped particles can reside in a second sample cell far removed ( approximately 3 mm) from the first cell. Such tweezers could be used for the simultaneous study of identically prepared ensembles of colloids and biological matter, and potentially offer enhanced control of 'lab-on-a-chip' and optically driven microstructures.     

光阱pN量级阱力的流体力学法测量系统

根据流体力学的分析 ,研究并计算了适合光镊操作生物粒子的无限大平板流场特性和流场分布 ,设计并研制了一套符合光镊pN(皮牛 )量级力测量的液体微循环系统和样品池 ,其液体微流量分流器和缓冲器解决了蠕动泵脉冲缺点 .实际测量和光阱力测试结果显示该系统满足光阱pN量级力的测量要求 .     

基于电动现象的细胞光镊阱力测量

提出了一种新的细胞光阱力标定的实验方法，利用细胞电泳原理，设计并研制了一套符合用光镊测力的电动样品池系统，用它替代单光镊操作系统中的普通样品池和高精密压电位移驱动平台，可以用电压调控细胞运动速度，系统相对简单、经济．实验测量结果为：在2～18V／cm电压梯度范围内，酵母细胞的运动速度与电压梯度成正线性关系，即在皮牛量级以下，最大光阱力与光镊光源的功率成线性增加关系．测量结果表明，该方法可实现对细胞光阱力的测量，还可用来测量细胞表面电量．     

光镊--光的力学效应的研究及应用

激光的发明使得光的力学效应走向了实际应用,光镊是光的力学效应的典型事例。简述了光镊技术的原理和特点——无损伤操控功能和微小力的传感器,介绍具有代表性的研究成果,并展望了光的力学效应研究和应用的发展。     

单光刀与单光镊激光微束系统

提出了构建一种用于细胞非接触操作的激光微束系统。该系统由 Nd:YAG激光束经声压、热膨胀、汽化等综合效应实现的光刀和 He- Ne激光束经光学动力学效应实现的光镊组成。将两激光束耦合到显微镜中 ,实现了生物细胞的捕获、移动、翻转、打孔等一系列操作。在此基础上 ,分析了形成光镊所必需产生梯度力场的条件和形成光刀对能量的要求 ,进行了系统的总体设计、关键部件设计和选择 ,构建了一套激光微束操作实验系统 ,得到了预期的试验结果。在该系统上成功地实现了非接触细胞操作 ,并对染色体进行了切割。     

Bead movement by single kinesin molecules studied with optical tweezers

Kinesin, a mechanoenzyme that couples ATP hydrolysis to movement along microtubules, is thought to power vesicle transport and other forms of microtubule-based motility. Here, microscopic silica beads were precoated with carrier protein, exposed to low concentrations of kinesin, and individually manipulated with a single-beam gradient-force optical particle trap ('optical tweezers') directly onto microtubules. Optical tweezers greatly improved the efficiency of the bead assay, particularly at the lowest kinesin concentrations (corresponding to approximately 1 molecule per bead). Beads incubated with excess kinesin moved smoothly along a microtubule for many micrometres, but beads carrying from 0.17-3 kinesin molecules per bead, moved, on average, only about 1.4 microns and then spontaneously released from the microtubule. Application of the optical trap directly behind such moving beads often pulled them off the microtubule and back into the centre of the trap. This did not occur when a bead was bound by an AMP.PNP-induced rigor linkage, or when beads were propelled by several kinesin molecules. Our results are consistent with a model in which kinesin detaches briefly from the microtubule during a part of each mechanochemical cycle, rather than a model in which kinesin remains bound at all times.     

Massively parallel manipulation of single cells and microparticles using optical images

The ability to manipulate biological cells and micrometre-scale particles plays an important role in many biological and colloidal science applications. However, conventional manipulation techniques--including optical tweezers, electrokinetic forces (electrophoresis, dielectrophoresis, travelling-wave dielectrophoresis), magnetic tweezers, acoustic traps and hydrodynamic flows--cannot achieve high resolution and high throughput at the same time. Optical tweezers offer high resolution for trapping single particles, but have a limited manipulation area owing to tight focusing requirements; on the other hand, electrokinetic forces and other mechanisms provide high throughput, but lack the flexibility or the spatial resolution necessary for controlling individual cells. Here we present an optical image-driven dielectrophoresis technique that permits high-resolution patterning of electric fields on a photoconductive surface for manipulating single particles. It requires 100,000 times less optical intensity than optical tweezers. Using an incoherent light source (a light-emitting diode or a halogen lamp) and a digital micromirror spatial light modulator, we have demonstrated parallel manipulation of 15,000 particle traps on a 1.3 x 1.0 mm2 area. With direct optical imaging control, multiple manipulation functions are combined to achieve complex, multi-step manipulation protocols.     

Tunable nanowire nonlinear optical probe

One crucial challenge for subwavelength optics has been the development of a tunable source of coherent laser radiation for use in the physical, information and biological sciences that is stable at room temperature and physiological conditions. Current advanced near-field imaging techniques using fibre-optic scattering probes have already achieved spatial resolution down to the 20-nm range. Recently reported far-field approaches for optical microscopy, including stimulated emission depletion, structured illumination, and photoactivated localization microscopy, have enabled impressive, theoretically unlimited spatial resolution of fluorescent biomolecular complexes. Previous work with laser tweezers has suggested that optical traps could be used to create novel spatial probes and sensors. Inorganic nanowires have diameters substantially below the wavelength of visible light and have electronic and optical properties that make them ideal for subwavelength laser and imaging technology. Here we report the development of an electrode-free, continuously tunable coherent visible light source compatible with physiological environments, from individual potassium niobate (KNbO3) nanowires. These wires exhibit efficient second harmonic generation, and act as frequency converters, allowing the local synthesis of a wide range of colours via sum and difference frequency generation. We use this tunable nanometric light source to implement a novel form of subwavelength microscopy, in which an infrared laser is used to optically trap and scan a nanowire over a sample, suggesting a wide range of potential applications in physics, chemistry, materials science and biology.     

A revolution in optical manipulation

Optical tweezers use the forces exerted by a strongly focused beam of light to trap and move objects ranging in size from tens of nanometres to tens of micrometres. Since their introduction in 1986, the optical tweezer has become an important tool for research in the fields of biology, physical chemistry and soft condensed matter physics. Recent advances promise to take optical tweezers out of the laboratory and into the mainstream of manufacturing and diagnostics; they may even become consumer products. The next generation of single-beam optical traps offers revolutionary new opportunities for fundamental and applied research.     

Measurements of leucocyte membrane elasticity based on the optical tweezers

A 1-μm in diameter polystyrene bead coated with lectin is trapped by optical tweezers whics is formed by a focused laser beam (740nm).A leucocyte adhered to the bottom of sample cell is chosen to close to the trapped bead.When their stable combination is confirmed,the leucocyte is displaced by moving the sample stage.A“tether”is then formed between the trapped bead and the membrane.The force acting on the tether is measured by a detector equipped on the optical tweezers system.The deformation of the membrane is diverse in different contact conditions.When the contact area is small,the tether is very thin and the force on it is 7.4pN(10^-12N),while the tether is much thicker under a larger contact area and its corresponding force is about 14pN.It is presumed that the latter is related to the deformation of cytoskeleton.