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| 基于梯度折射率光子晶体可调谐亚波长聚焦特性的研究 |
| Tunable sub-wavelength focusing properties in gradient negative refractive index photonic crystals |
| 投稿时间：2022-03-02 |
| DOI：10.3969/j.issn.1005-5630.2022.006.005 |
| 中文关键词: 梯度折射率光子晶体 FDTD算法 亚波长聚焦 半宽 |
| 英文关键词:gradient index photonic crystals FDTD algorithm sub-wavelength focusing half-width |
| 基金项目:国家自然科学基金（61975122） |
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| 中文摘要: |
| 本文对梯度折射率光子晶体的亚波长聚焦特性进行了研究。该光子晶体是由硅和圆形空气孔构成的平行平板，通过改变空气孔的结构来实现折射率的梯度渐变。采用时域有限差分（finite-different time-domain，FDTD）算法对光子晶体的聚焦过程进行仿真分析。研究发现，适当地修正光程差可以大大地提高聚焦效果，同时焦距和中心空气孔的结构对聚焦效果也有影响。综合以上3种要素，最终设计出的梯度折射率光子晶体平板可实现较好的亚波长聚焦效果，其中在光子晶体外部1.45 λ处的光斑最佳，半宽值可达到0.3447 λ。为了提升应用性能，设计了一个动态的调焦系统。在该光子晶体中加入半导体制冷片来调节温度，通过改变温度可以实现1.1374 λ～2.6264 λ的焦点调谐，同时焦斑半宽均小于0.4 λ。 |
| 英文摘要: |
| The focus of this paper is the sub-wavelength imaging of gradient index photonic crymstals. The gradient index photonic crystals is a parallel plate composed of silicon and circular air holes. The gradient change of photon crystal refractive index is realized by adjusting the structure of each column of pores. The focusing process of the gradient index photonic crystals is simulated by finite-different time-domain (FDTD) algorithm. The results showed that proper modification of the optical path difference could greatly optimize the focusing effect. Furthermore, changing the focal length of photonic crystals and the structure of the central air hole could also optimize the focusing effect. By combining the above three elements, the gradient index photonic crystal was finally designed which could realize sub-wavelength focusing. The half-width of the focused spot was 0.3447 λ , which was located at 1.45 λ outside the photonic crystal. To improve application performance, a dynamic focal length adjustment system was designed on the gradient index photonic crystals. The focal length range of 1.1374 λ～2.6264 λ could be adjusted without changing the structure of gradient index photonic crystals. Meanwhile, the half-width of the focal spot was less than 0.4 λ. |
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