Sun-flower型渐变光子晶体自聚焦透镜

大多数渐变光子晶体渐变透镜都是以正方晶格或三角晶格排布为基础，并且多选择硅或二氧化硅等高折射率材料，研究的波段多为红外波段。随着可见光通信技术的发展，在可见光波段研究低折射率材料的自聚焦透镜变得很有意义。为了迎合这种需求，提出了Sun-flower型渐变光子晶体自聚焦透镜。首先，通过比较TE和TM两种偏振模式Sun-flower渐变光子晶体朗伯透镜在可见光波段的会聚强度，发现TM型的会聚效果远远优于TE型。然后，以TM型Sun-flower渐变光子晶体为基础设计圆柱形自聚焦平板透镜，通过光场传输的模拟计算给出平板透镜在可见光波段自聚焦的拍长，进一步优化平板透镜会聚光强设计透镜的层数，结果表明在层数为22时效果最佳。最后，讨论了列数的减少对平板透镜的影响，结果表明随着列数的减少光强减弱。这对于制作出高性能会聚效果、短焦距、小体积的光学集成器件有重要的指导意义。

Self-focusing lens in Sun-flower graded photonic crystal

Most photonic crystal lens based on square or triangular lattice usually uses high refractive index materials such as Si or SiO2. And the study on such lens has been focused on the infrared wavelength range. With the development of the visible light communication technology, the research of Sun-flower self-focusing lens with low refractive index materials in visible band becomes very meaningful. To meet that requirements, self-focusing lens based on Sun-flower shaped graded PC was proposed. Firstly, by comparing the convergence intensity of this proposed lens between TE-polarized and TM-polarized mode, the convergence effect of TM polarization was superior to the convergence effect of TE polarization. Then self-focusing flat lens based on TM mode Sun-flower graded PC was designed. The beat length of the flat lens was given by the simulation of optical field transmission. The layers of the flat lens were optimized, and the best number of the layers was 22. In the end, the influence of the number of columns was discussed. The results show that the intensity decreases as the number of columns reduces. It has great guiding significance to make optical integrated devices with high-performance convergence effect, short focal length and small volume.