Near-Zero-Index Slabs on Bloch Surface Wave Platform for Long-Range Directional Couplers and Optical Logic Gates
Near-Zero-Index Slabs on Bloch Surface Wave Platform for Long-Range Directional Couplers and Optical Logic Gates
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DOI：
10.1021/acsnano.1c08318
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发表时间：
2022-02-22
期刊：
影响因子：
17.1
通讯作者：
Delaunay, Jean-Jacques
中科院分区：
文献类型：
--
作者：
Deng, Chih-Zong;Ho, Ya-Lun;Delaunay, Jean-Jacques
近零折射率材料和结构具有无相位传播的特殊光学特性，可产生定向辐射，为光子集成电路中的定向耦合和光逻辑门提供了一种可能的途径。然而，来自近零折射率结构的辐射仅限于几百纳米的短范围。布洛赫表面波（Bloch surface wave，BSW）是一种电磁表面波，可以在全电介质多层膜和具有低损耗光学模式的电介质之间的界面处激发，它提供了一种增加传播长度的解决方案。在这项工作中，我们提出了一个纳米结构的近零折射率板集成在全介质无金属BSW平台的远程表面波辐射。利用长程定向表面波辐射，实现了基于近零折射率片的定向耦合器和光学逻辑门。所提出的定向耦合器实现了长耦合距离（输入板和输出板之间的电场幅度比为0.22，具有50 μ m的耦合距离），这比基于倏逝波耦合的常规定向耦合器长2个数量级。通过控制板之间的BSW的干涉图案，XOR逻辑门实验证明在电信波长具有27.9 dB的显著消光比。背波近零折射率逻辑门和具有长距离光传输的定向耦合器为光子集成电路和基于无金属表面波的应用的发展提供了一种途径。
Near-zero-index materials and structures, with their extraordinary optical behaviors of phase-free propagation resulting in directional radiation, provide a possible approach for directional coupling and optical logic gates in photonic integrated circuits. However, the radiation from the near-zero-index structures is limited to a short range of a few hundreds of nanometers. A Bloch surface wave (BSW), an electromagnetic surface wave that can be excited at the interface between an all-dielectric multilayer and a dielectric medium with a low-loss optical mode, provides a solution to increase the propagation length. In this work, we present a nanostructured nearzero-index slab integrated on the all-dielectric metal-free BSW platform for long-range surface wave radiation. By employing the long-range directional surface-wave radiation, a directional coupler and optical logic gates based on the BSW near-zero-index slabs are realized. The proposed directional couplers achieve long coupling distances (the electric-field magnitude ratio between the input slab and output slab is 0.22 with a 50 mu m coupling distance), which is 2 orders of magnitude longer than that of conventional directional couplers based on evanescent wave coupling. By controlling the interference pattern of the BSW between the slabs, the XOR logic gate is experimentally demonstrated with a significant extinction ratio of 27.9 dB at telecommunications wavelengths. The BSW near-zero-index logic gates and the directional coupler with long-range light propagation provide an approach to the development of photonic integrated circuits and metal-free surface wave-based applications.