Department of Physics, Baylor University, Waco, TX, 76798, United States.
The Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX, 77843, United States.
Sci Rep. 2018 Feb 5;8(1):2342. doi: 10.1038/s41598-018-19633-2.
We report a novel optical waveguide design of a hollow step index fiber modified with a thin layer of indium tin oxide (ITO). We show an excitation of highly confined waveguide mode in the proposed fiber near the wavelength where permittivity of ITO approaches zero. Due to the high field confinement within thin ITO shell inside the fiber, the epsilon-near-zero (ENZ) mode can be characterized by a peak in modal loss of the hybrid waveguide. Our results show that such in-fiber excitation of ENZ mode is due to the coupling of the guided core mode to the thin-film ENZ mode. We also show that the phase matching wavelength, where the coupling takes place, varies depending on the refractive index of the constituents inside the central bore of the fiber. These ENZ nanostructured optical fibers have many potential applications, for example, in ENZ nonlinear and magneto-optics, as in-fiber wavelength-dependent filters, and as subwavelength fluid channel for optical and bio-photonic sensing.
我们报告了一种新型的中空阶跃折射率光纤的光波导设计，该光纤采用了一层很薄的氧化铟锡（ITO）。我们在ITO 介电常数接近零的波长附近展示了在该光纤中高度限制的波导模式的激发。由于在光纤内部的薄 ITO 壳内的高场限制，ε近零（ENZ）模式可以通过混合波导的模态损耗中的峰值来表征。我们的结果表明，这种光纤内的 ENZ 模式激发是由于导芯模式与薄膜 ENZ 模式的耦合。我们还表明，发生耦合的相位匹配波长取决于光纤中心孔内组成部分的折射率。这些 ENZ 纳米结构光纤具有许多潜在的应用，例如在 ENZ 非线性和磁光领域，例如作为光纤中波长相关的滤波器，以及作为亚波长流体通道用于光学和生物光子学传感。
