【作者】 王仕旺；

【导师】 付神贺；

【作者基本信息】 暨南大学 ， 光学工程（专业学位）， 2020， 硕士

【摘要】 由于光的衍射和色散效应,成像系统存在一定的衍射极限,传统的分辨极限已无法满足科学研究者的需求,如何从本质上突破衍射极限,是当前研究的首要问题。自21世纪以来,主要从近场和远场两个方面来提高空间分辨率,近场技术主要是收集物体表面逐渐衰减的倏逝波,从而得到波场的精细结构。远场技术主要是通过激发的荧光分子标记物体,再精确定位荧光实现远场成像。但近场技术受到工作距离的限制,远场技术需要特殊的染料,都不能被广泛应用。随着在提高空间分辨率上的探索,超振荡现象进入科研者的研究视野,不依赖于倏逝场的情况下,光场的超精细结构可以传播到远场,并且无需特殊染料,为远场成像提供了新的途径。随后大量利用超振荡效应的远场聚焦微结构被设计出来,虽然可以得到突破衍射极限的聚焦光斑,但是光斑的周围不可避免地伴随着高强度旁瓣,并且需要复杂的算法去优化结构,限制了微结构的潜在应用。在此,我们设计了一种超振荡结构,无需优化算法,基于锐边衍射原理产生的超振荡波场能在远场得到无旁瓣的聚焦光斑,打破了超振荡特征尺寸与伴随高强度旁瓣的平衡。本文讨论了一维和二维无旁瓣超振荡光场的产生,具体内容为:第一,提出一种产生超振荡结构波场的新原理,即几何锐边衍射原理。几何锐边衍射诱导的高频分量在传播空间相干叠加得到聚焦光斑,依据该原理,我们设计了双月形锐边结构,首先介绍了该结构的设计步骤和工艺加工过程。其次,从理论和实验上研究了该结构产生超聚焦光场的机理,在结构的中心可以得到突破衍射极限的聚焦光斑,并且光斑在y方向没有旁瓣的产生。我们进一步得到该结构传播过程中不同位置的相位图分布,由中心区域的相位振荡频率验证该结构的超振荡效应。最后发现聚焦光斑的尺寸和位置与结构参数大小有关。第二,在一维无旁瓣超振荡光场的基础上,我们设计双月对形锐边结构,该结构由一对双月形组成,其独特的设计使得聚焦光斑在二维方向上没有旁瓣的产生。我们利用快速傅里叶算法进一步验证该结构的聚焦特性,并分析结构参数的影响。结构的尺寸同比例增大时,生成相同的聚焦光斑将在更远的位置,进一步推动远场超分辨成像的发展。更多还原

【Abstract】 Due to the diffraction and dispersion effects of light,the imaging system has diffraction limit.The traditional resolution limit can no longer meet the needs of scientific researchers,how to break through the diffraction limit in essence is the primary problem of current research.Since the 21 st century,the spatial resolution has been mainly improved from the aspects of the near and the far fields.The near-field technology mainly collects evanescent waves that gradually decay on the surface of the object to obtain the fine structure of the wave field.On the other hand,far-field imaging is achieved by labeling objects with excited fluorescent molecules and then precisely positioning the fluorescence.However,the near-field technology is limited by the working distance,while the far-field technology requires special dyes,which cannot be widely used.During the exploration of improving the spatial resolution,the phenomenon of super-oscillation has entered the research field,under the condition that the light field is not dependent on evanescent field,the ultra-fine structure of the light field can be propagated to the far field without special dyes,which provides a new way for far-field imaging.Subsequently,a large number of far-field focusing microstructures using the super-oscillation effect were designed,although a focused spot can be obtained that breaks the diffraction limit,the spot is inevitably accompanied by highintensity side lobes,and the design requires complex algorithms to optimize the structure,this limits the potential applications of microstructures.Here,we design a superoscillating structure without the need of optimization algorithm.The superoscillating wave field generated based on the principle of sharp-edge diffraction can obtain a focused spot without sidelobes in the far field,which breaks the balance between the superoscillating main lobe and the accompanying side lobe.Therefore,this thesis investigates the generation one-dimensional and two-dimensional side-lobefree super-oscillating light fields.The specific content is:Firstly,a new principle for generating the wave field of the super-oscillation structure is proposed,namely the principle of geometric sharp edge diffraction.The high-frequency components induced by geometric sharp-edged diffraction are coherently superimposed in the propagation space to obtain a focused spot.Based on this principle,we designed a bi-moon-like sharp-edged structure.Firstly,the design steps and process of the structure are introduced.Next,the generation of super-focusing light field by the structure is studied theoretically and experimentally.A focused spot that breaks through the diffraction limit can be obtained in the center of the structure,and there is no side lobe accompanied in the y direction.We further obtain the phase map distribution at different positions during the propagation of the structure,and verify the superoscillating effect of the structure by measuring the phase oscillating frequency in the central region.Finally,it was found that the size and position of the focused spot are related to the size of the structural parameters.Secondly,on the basis of the one-dimensional side-lobe-free superoscillating light field,we design two pairs of moon-like structure in x-y space,its unique design makes the focused spot have no sidelobe in the two-dimensional direction.We use the fast Fourier algorithm to further verify the focusing characteristics of the structure and analyze the influence of the structure parameters.When the size of the structure increases in the same proportion,the same focused spot will be generated at a further distance,which will further promote the development of far-field super-resolution imaging.更多还原