基于光学变换的光学隐身、纳米成像和聚焦器件的研究

发布时间：2018-11-11 19:18

【摘要】：2006年Pendry教授提出了基于麦克斯韦方程组协变性的光学变换,使得很多存在于科幻小说中的光学器件,例如光学隐身、光学黑洞等,都具有了实现的可能,从此开启了光学变换设计光学器件的新纪元。十几年来,伴随着异向介质的蓬勃发展和光学变换理论的创新,光学变换成为现代光学中设计光学器件不可或缺的重要方法之一。本文以光学隐身、纳米成像和聚焦器件的研究为背景,着重讨论了基于光学变换的光学器件的设计与实现。本文首先介绍了光学隐身、纳米成像和聚焦器件的研究现状。由于纳米加工工艺的制约,无法实现基于光学变换的“完美”光学器件所需要的异向介质单元结构,限制了器件所能实现的性能。而依据现有纳米加工工艺所设计和实现的光学器件,由于其简化的材料参数,往往伴随着器件结构尺寸小、工作频率单一、对损耗敏感等一系列问题。针对以上科学问题,本论文做了如下几个方面的工作:1.针对光学隐身器件隐身区域小的科学问题,本文基于光学坐标变换和光学保角变换,提出了一种不受各向异性因数限制的隐身器件的设计方法,用于实现大尺度物体的隐身。基于这个方法,本文在远红外频段首次设计并验证了能够躲避热探测的远红外隐身器件。2.针对纳米成像透镜不利于暗视场应用的科学问题,本文提出了一种暗视场纳米成像透镜设计,该透镜由第一类和第二类双曲型异向介质构成,其中第二类双曲型异向介质能有效地阻止低波矢的光通过,进而提高像的对比度。3.针对纳米成像透镜工作频率单一、对损耗敏感的科学问题,本文基于虚部坐标变换和折叠几何变换,提出了纳米成像透镜的设计方法,揭示了利用反常色散双曲型异向介质实现宽频纳米成像的工作原理,并给出了相应的设计结构。4.针对纳米成像透镜制备需要复杂的纳米加工工艺的科学问题,依据石墨烯紫外频段光学性质不会由于弯曲、拉伸或随机堆叠而改变的特性,本文提出了利用石墨烯实现纳米成像透镜的设计方法。该透镜具有灵活性,适用于任意形状的基底,极大程度地降低了透镜制备的难度。5.针对纳米聚焦技术不易实现的科学问题,本文提出了一种具有高聚焦性能的纳米聚焦透镜设计方法。依据高阶光学变换、虚部坐标变换和圆柱等效介质理论,本文对纳米聚焦透镜的性能进行了优化,并提出了利用金属和介质圆柱层状结构构造径向渐变的透镜参数的方法,用以实现边界阻抗匹配,提高透镜的聚焦性能。6.针对纳米聚焦结构具有几何奇点的科学问题,本文提出了利用圆柱双曲型异向介质实现宽频聚焦的设计方法。本文发现,在利用光学保角变换将平板双曲型异向介质变换到圆柱双曲型异向介质的过程中,可以避免几何奇点的引入。
[Abstract]:In 2006, Professor Pendry proposed a covariant optical transformation based on Maxwell's equations, which makes it possible for many optical devices in science fiction, such as optical stealth, optical black hole, etc. This opened a new era in optical transformation design of optical devices. In the past ten years, with the vigorous development of dielectrics and the innovation of optical transformation theory, optical transformation has become one of the indispensable and important methods for designing optical devices in modern optics. In this paper, the design and implementation of optical devices based on optical transformation are discussed based on the research of optical stealth, nano-imaging and focusing devices. This paper first introduces the research status of optical stealth, nano-imaging and focusing devices. Due to the restriction of nano-fabrication technology, it is impossible to realize the "perfect" optical device based on optical transformation, which can not realize the structure of the "perfect" optical device, which limits the performance of the device. Because of its simplified material parameters, the optical devices designed and realized according to the existing nanofabrication technology are often accompanied by a series of problems, such as small structure size, single operating frequency, sensitive to loss and so on. In view of the above scientific problems, this paper has done the following work: 1. Based on the optical coordinate transformation and the optical conformal transformation, a design method of the stealth device which is not restricted by the anisotropic factor is proposed in this paper, which is used to realize the stealthy of a large scale object in view of the scientific problem of the small stealth region of the optical stealth device, which is based on the optical coordinate transformation and the optical conformal transformation. Based on this method, a far-infrared stealth device, which can avoid thermal detection, is designed and verified for the first time in the far-infrared band. Aiming at the scientific problem that nanometer imaging lens is not conducive to dark field application, a design of dark field nanometer imaging lens is presented in this paper. The lens is composed of two kinds of hyperbolic dielectrics. The second kind of hyperbolic dielectrics can effectively prevent the light from passing through the low wave vector and then improve the contrast of the image. Aiming at the scientific problem that the working frequency of nano-imaging lens is single and sensitive to loss, a design method of nano-imaging lens is proposed based on virtual coordinate transformation and folded geometric transformation. The working principle of using anomalous dispersion hyperbolic dielectrics to realize broadband nanometer imaging is revealed, and the corresponding design structure is given. In view of the scientific problem that the preparation of nano-imaging lens requires complex nano-fabrication technology, according to the characteristics that the optical properties of graphene ultraviolet band can not be changed by bending, stretching or random stacking, In this paper, a design method of nano-imaging lens using graphene is presented. The lens is flexible and suitable for any shape of substrate, which greatly reduces the difficulty of lens preparation. In order to solve the problem that nano-focusing technology is not easy to be realized, a design method of nano-focusing lens with high focusing performance is proposed in this paper. Based on high-order optical transformation, virtual coordinate transformation and cylindrical equivalent medium theory, the performance of nano-focusing lens is optimized in this paper, and a method of constructing radial gradient lens parameters using metal and dielectric cylindrical layered structure is proposed. In order to achieve boundary impedance matching, improve the focusing performance of the lens. 6. In order to solve the problem of geometric singularities in nanoscale focusing structures, a design method of wide frequency focusing using cylindrical hyperbolic dielectrics is proposed in this paper. In this paper, it is found that the introduction of geometric singularities can be avoided in the process of converting a flat plate hyperbolic anisotropic medium to a cylindrical hyperbolic anisotropic medium by optical conformal transformation.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TH74

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