基于微透镜和光子晶体的可调焦亚波长成像系统研究
Research on a Tunable Subwavelength Imaging System Based on Micro-Lenses and Photonic Crystals

光束聚焦到亚波长分辨率的聚焦光斑具有非常重大的研究意义，尤其是随着超大规模集成电路的发展，像光信息存储、纳米光刻、光学显微镜等领域都需要聚焦光斑到亚波长，本文旨在实现更小的聚焦光斑和更高分辨率的远场成像，为以上领域提供一些参考价值。文中研究了单个硅微球的亚波长聚焦特性，采用半个椭圆透镜与平凸透镜相结合的组合微透镜，使得入射光能够保持在出射面外部的近场形成良好的亚波长成像。随后通过将组合微透镜和光子晶体结合构成系统，在组合微透镜优秀的亚波长聚焦能力的基础上，再借助光子晶体的负折射效应把组合微透镜在近场的焦斑传播的更远，并通过优化系统的上下边缘和各类参数，使得焦点半宽达到0.3257个波长。该系统通过调整组合微透镜与光子晶体下表面距离，可以有效减小6.1%的焦点半宽，通过适当调节环境温度可以有效改善聚焦效果，使得焦点半宽进一步减小到0.2818个波长，实现了良好的亚波长聚焦效果。
Beam focusing to sub-wavelength resolution of the focused spot has very significant research significance, especially with the development of ultra-large-scale integrated circuits, like optical information storage, nanolithography, optical microscopy and other fields need to focus the spot to the sub-wavelength. This paper aims to achieve a smaller focused spot and higher resolution far-field imaging, to provide some reference value for the above fields. In the paper, the subwavelength focusing characteristics of a single silicon microsphere are investigated, and a combined microlens combining half an ellipsoidal lens and a plano-convex lens is used, which enables the incident light to be kept in the near-field outside the emitting surface to form a good subwavelength imaging. Subsequently, by combining the combined microlens and photonic crystal to form a system, on the basis of the excellent subwavelength focusing ability of the combined microlens, the focal spot of the combined microlens in the near field is propagated farther with the help of the negative refractive effect of the photonic crystal, and by optimizing the upper and lower edges of the system and all kinds of parameters, the focal spot half-width reaches 0.3257 wavelengths. By adjusting the distance between the combined microlens and the lower surface of the photonic crystal, the system can effectively reduce the focal spot half-width by 6.1%, and by adjusting the ambient temperature appropriately, the focusing effect can be effectively improved, so that the focal spot half-width can be further reduced to 0.2818 wavelengths, which realizes a good sub-wavelength focusing effect.