基于金微环谐振器的表面等离子体光镊研究
中文摘要
目前，光镊技术凭借非接触操作、精确度高、无机械损伤等优点被广泛应用于物理、化学和生物等研究领域中。而基于表面等离子体共振现象的近场光镊利用倏逝场梯度，能够突破衍射极限并增大光捕获力，表现出了比传统激光光镊更优异的性能。在现有的研究基础上，人们越来越关注如何在低功率下得到更大的光捕获力，以实现更为复杂的微粒操控。
本文介绍了一种可以捕获和驱动介质纳米粒子的跑道型金微环谐振器结构，利用其谐振特性对金膜表面激发的表面等离子体波进行增强，从而捕获微粒并驱动其以恒定的速度绕跑道转动。通过数值有限元方法和麦克斯韦应力张量积分讨论了介质纳米颗粒所受的光学力，在相同的输入功率下，半径为50nm的粒子在金跑道型微环谐振器上所受到的光学力及运动速度是在直波导上的3~5倍。本文详细讨论了单个纳米粒子在微谐振器不同位置处的运动行为，为捕获和操纵多个纳米粒子并预测它们的运动轨迹提供更多的细节。
如何防止表面等离子体波在传播方向迅速衰减是近场光捕获需要解决的关键问题之一。本文设计了一个以金微环谐振器为关键器件、以表面等离子体波的相长干涉为核心的近场光镊。该结构利用在金表面激发的表面等离子体波捕获介电纳米颗粒，而表面等离子体波在微环谐振器中的相长干涉作用能够极大增
强局部光场，从而提高捕获粒子所需的梯度力，并驱动其围绕跑道结构旋转。
本文结合微粒的布朗运动与光力作用，得出了克服微粒布朗运动所需最小势阱，从而得到装置能够稳定捕获的最小功率。利用经典DLVO理论计算了聚苯乙烯微粒与波导间的纵向相互作用势，直接从微观层次验证了结构假设的正确性。对于溶液浓度及温度对捕获力的影响也进行了一定的分析。
本文利用斯托克斯粘滞阻力公式计算了微粒绕轨道转动的速度，并讨论了单个纳米微粒在微环不同位置时的运动行为及详细捕获情况，为预测多个微粒运动轨迹提供了理论依据。利用有限元法及麦克斯韦应力张量法，结合仿真具体讨论了影响捕获力大小和微粒速度的因素。文章最后，预测了多个微粒的捕获情况及运动状态，分析了实际加工情况，设计了光栅激发结构，并对三维模型进行了仿真。本文所提出的这种金微环谐振器结构可以进一步增大光捕获力，有望在芯片上实现纳米粒子的全光捕获和其他交叉学科研究。
香煎三文鱼关键词：光操纵，表面等离子体，微环谐振器，运动行为
The Rearch of Surface Plasmon Optical Tweezers with Au Micro-Racetrack Resonator
Abstract
At prent,becau the advantages of non-contact,high accuracy and no mechanical damage, optic
al tweezers technique has been widely ud in the fields of physics,chemistry,biology and so on.The near-field optical tweezers bad on surface plasmon resonance(SPR),which us the evanescent field gradient,can break through the diffraction limit and increa the optical trapping force.On the basis of the existing rearch,people pay more and more attention to producing greater optical trapping force with low incident power,so as to achieve more complex particle manipulation.
In this article,we design a gold micro-racetrack resonator(Au-MRR)which can enhance the surface plasmon waves(SPWs)excited on gold,thus tightly trap and drive the dielectric nanoparticle to rotate around the circuit of racetrack with an adjustable velocity.The optical forces applied on dielectric nanoparticle are discusd by utilizing the Maxwell’s stress tensor integration with a numerical Finite Element Method.At the same level of input power,the velocity of particle with radius of50nm driven by optical forces on Au-MRR is3to5times larger than that on a straight waveguide.Further we explore the motion behavior of single nanoparticle lies on different position of Au-MRR,which can provide the details to trap and manipulate multiple nanoparticles and predict their trace of movement.
One of the key problems needs to be solved is how to reducing the rapid attenuation of the SPWs in the propagation direction.In this work,we design an on-chip optical trapping system compod of a gold micro-racetrack resonator(Au-MRR)and a SPWs launch device.When the excited SPWs meet t
he constructive interference condition related with perimeter of Au-MRR,it exhibits an enhanced optical field around the inner surface of metal,which is great helpful to strengthen the optical forces.
In this paper,the minimum trapping potential resulting from the optical forces is calculated to overcome the Brown motion of the particle,thus the required minimum input power intensity can be obtained,which can prevent the overheating damaging the structure.The classical DLVO theory is ud to calculate the longitudinal interaction potential between the polystyrene particles and the
waveguide,verifying the correctness of the structural hypothesis from the microscopic level directly.
Further we discuss the optical forces exerted on the nanoparticle,who lies on difference positions,related with its instant velocity to analysis its motion behavior in details.The velocity of trapped particle to move around the micro-racetrack depends on the radius of nanoparticle and power to excite surface plasmon polaritons(SPPs)in the MRR.Moreover,we predict the situation of capturing veral particles and trend of particles’movement.In the end,according to the actual processing conditions,the excitation mode of the SPWs is changed to the grating structure.We simulates the three-dimensional simulation,which provides the reference value for the actual processing.This optimum geometry of Au-MRR allows further enhancement of the optical forces whic
h is expected to realize all-optical on-chip manipulation of nanoparticles,biomolecules,and many other nanomanipulation applications.洋溢着笑容
Key words:Optical manipulation,surface plasmon waves,micro-racetrack resonator,motion behavior
目录
中文摘要.......................................................................................................II 第一章引言. (1)
1.1研究背景 (1)
1.2近场光镊的研究现状及应用 (2)
1.3微环谐振器光力器件的研究现状 (3)
1.4本文的主要工作内容与创新点 (5)
第二章微环谐振器表面等离子体光镊理论基础 (7)
2.1表面等离子体激元的特性与激发 (7)
2.1.1表面等离子体激元简介 (7)
治感冒的中药2.1.2表面等离子体激元的特性 (7)
2.1.3表面等离子体激元的激发 (9)
2.2光镊的基本原理 (10)
2.2.1几何光学模型 (10)
2.2.1电磁散射模型 (11)
2.3微环谐振器的理论基础 (12)
2.4本章总结 (14)
第三章基于金微环谐振器的表面等离子体光镊的设计 (16)
3.1理论模型 (16)
花姿倾城
左右后视镜正确位置图3.2几何结构参数及表面等离子体波的谐振条件 (17)
3.3光捕获力及光阱的计算 (20)
3.4基于DLVO理论的微粒纵向势能及捕获状态分析 (23)
3.4.1微粒与波导间的引力-范德华吸引力 (24)猪肚的做法大全
3.4.2微粒与波导间的排斥力 (24)
3.4.3微粒的位能曲线与捕获情况 (24)
3.5金微环谐振器等离子体光镊与现有光镊的对比 (25)
3.5.1与直波导等离子体光镊的对比 (25)
3.5.2与传统硅微环谐振器光镊的对比 (28)
3.6本章总结 (28)
第四章微粒运动情况分析及实际加工设计 (30)
4.1微粒的运动速度与影响因素 (30)
4.1.1入射光功率对微粒速度的影响 (30)
4.1.2微粒半径对微粒速度的影响 (31)
大连有什么好玩的地方
4.2微粒在微环谐振器上的旋转情况 (31)
4.3溶液浓度与温度对捕获的影响 (34)
4.4多个微粒的运动情况 (35)
4.5初步结构加工设计及三维仿真 (36)
4.6本章总结 (38)
第五章结论与展望 (40)
5.1主要结论 (40)
5.2展望 (41)芦衣顺母的故事
参考文献 (42)
在学期间的研究成果 (45)
致谢 (46)
