Shi Xueliang, Liu Juan, Peng Weiting, Hu Bin, Wang Yongtian
Opt Express. 2019 Oct 28;27(22):32242-32252. doi: 10.1364/OE.27.032242.
In this paper, a switchable micro-focusing Fresnel device based on phase-change materials (PCMs) is proposed, which can selectively display the functions of transmission and reflection without the use of mechanical adjustment on micro scale. The switchable function is realized by combining Fresnel structure with PCM. A four-level switchable Fresnel device consisting of a typical PCM GeSbTe (GST-326) is designed to focus light into a focal length of 30 µm at wavelength of 3.1 µm. The optical performance of the switchable device has been analyzed by using finite-difference time-domain (FDTD) method, showing bright convergence point near pre-designed focal length with focusing efficiencies larger than 18%, depth of focus (DOF) less than 4.65 µm and the full width at half-maximum (FWHM) not larger than 1.30 µm. Furthermore, by precisely manipulating the variation of PCM thickness, we also obtain a device that possesses the characteristics of a transmission-reflection focusing beam splitter. The devices show good potential for the combination of traditional binary optical devices and PCM to produce new functions, and provides a promising innovative approach for miniature focal length switching device.
本文提出了一种基于相变材料（PCM）的可切换微聚焦菲涅耳器件，该器件无需在微观尺度上进行机械调节，就能选择性地展现透射和反射功能。可切换功能通过将菲涅耳结构与PCM相结合来实现。设计了一种由典型的PCM锗锑碲（GST - 326）组成的四级可切换菲涅耳器件，用于在波长为3.1 µm时将光聚焦到30 µm的焦距。采用时域有限差分（FDTD）方法分析了该可切换器件的光学性能，结果表明在预设计焦距附近出现明亮的会聚点，聚焦效率大于18%，焦深（DOF）小于4.65 µm，半高宽（FWHM）不大于1.30 µm。此外，通过精确控制PCM厚度的变化，我们还获得了一种具有透射 - 反射聚焦分束器特性的器件。这些器件显示出传统二元光学器件与PCM相结合以产生新功能的良好潜力，并为微型焦距切换器件提供了一种有前景的创新方法。
