基于超短脉冲激光的纳米粒子捕获

发布时间：2018-09-04 06:43

【摘要】：光镊技术是利用一束强聚焦的激光光束作为光源,激光照射到粒子上时,光束会产生作用于粒子上的辐射力,从而捕获和操纵微粒的一项技术。常说的光镊就是单光束梯度力光阱,激光光束经过聚焦,在已聚焦的光束束腰的附近产生很高的场强梯度形成力,这种力的量级达到皮牛顿,依靠这个力来三维稳定捕获和操控微粒。因此,激光束对粒子的辐射力的研究就十分重要。近年来大量的新型激光束被应用到作用于微粒的辐射力的研究上,研究范围也从连续波激光束扩展至超短脉冲激光束。因此本文分别研究了连续激光波光镊和超短脉冲激光波光镊,本文的重点工作如下：1、在反常涡旋光束的传输特性的基础上,详细分析了聚焦的反常涡旋光束在近轴限制下对瑞利介质球的捕获的影响,并且讨论了反常涡旋光束不同的拓扑荷数和光束阶数在辐射力上的影响。基于瑞利散射理论在理论上和数值上分析了近轴近似情况下反常涡旋光束对纳米粒子的辐射力,显示了一束具有合适的光束阶数和拓扑荷数的强聚焦的反常涡旋光束,可以用来捕获和操纵一个绝缘的球形纳米粒子,这个介质球的折射率可以是大于或者小于周围的环境。另外还详细讨论了反常涡旋光束的阶数和拓扑荷数的不同对于辐射力的影响。不仅如此,本文还着重分析了稳定捕获瑞利粒子的条件。2、本文进一步提出用脉冲激光取代传统连续激光脉冲激光作为光源来捕获纳米粒子。在理论上重点研究了脉冲光镊作用于粒子上的辐射力,对脉冲持续时间,光束阶数和拓扑荷数三个参数对于辐射力的影响做了重点分析,并且在稳定捕获纳米粒子的前提下对脉冲激光光束的要求做了深入分析。结果表明,对于给定的粒子脉冲间隔与脉冲持续时间的比例应选用严格,除此之外有些参数也存在于传统连续光镊中。
[Abstract]:Optical tweezers technology is a technique that uses a strong focused laser beam as a light source. When a laser shines on a particle, the beam will produce a radiation force acting on the particle, thus capturing and manipulating the particles. Optical tweezers are often referred to as single beam gradient force trapping, where a laser beam is focused and produces a very high field intensity gradient formation force near the waist of a focused beam, which is of the order of magnitude of Pi Newton. This force is used to stabilize the capture and control of particles in three dimensions. Therefore, it is very important to study the radiation force of laser beam to particles. In recent years, a large number of new laser beams have been applied to the study of radiation force acting on particles, and the research scope has been extended from CW laser beam to ultrashort pulse laser beam. Therefore, the CW and ultrashort pulse laser tweezers are studied in this paper. The emphasis of this paper is as follows: 1, on the basis of the propagation characteristics of anomalous vortex beams, The influence of focused anomalous vortex beam on the capture of Rayleigh dielectric sphere is analyzed in detail, and the effects of different topological charge numbers and beam order of anomalous vortex beam on radiation force are discussed. Based on Rayleigh scattering theory, the radiation force of anomalous vortex beam on nanoparticles in paraxial approximation is analyzed theoretically and numerically. A beam of strongly focused anomalous vortex beams with appropriate beam order and topological charge is shown. It can be used to capture and manipulate an insulating spherical particle whose refractive index can be greater or smaller than the surrounding environment. In addition, the effects of the order of anomalous vortex beam and the topological charge on the radiation force are discussed in detail. In addition, the condition of stable capture of Rayleigh particles is analyzed in this paper. Furthermore, it is proposed to replace the conventional continuous laser pulse laser with pulsed laser as a light source to capture nanoparticles. The effects of pulse duration, beam order and topological charge on the radiation force are analyzed. Furthermore, the requirement of pulsed laser beam is analyzed on the premise of stable capture of nanoparticles. The results show that the ratio of particle pulse interval to pulse duration should be strictly selected, and some parameters also exist in traditional continuous optical tweezers.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;TN249

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