Negative refraction might occur at the interface between a two-dimensional photonic crystal (PhC) slab and a homogeneous medium, where the guiding of the electromagnetic wave along the third dimension is governed by total internal reflection. Herein, we report on the observation of negative refraction in the PhC slab where the vertical guiding is enabled by a bound state in the continuum and essentially beyond the light cone. Such abnormal refraction and guiding mechanism are based on the synchronous crafting of spatial dispersion and the radiative lifetime of Bloch modes within the radiative continuum. Microwave experiments are provided to further validate the numerical proposal in an all-dielectric PhC platform. It is envisioned that the negative refraction observed beyond the light cone might facilitate the development of optical devices in integrated optics, such as couplers, multiplexers, and demultiplexers.

中文翻译：

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连续介质中束缚态介导的负折射

负折射可能发生在二维光子晶体 (PhC) 板和均匀介质之间的界面处，其中电磁波沿第三维的引导由全内反射控制。在这里，我们报告了对 PhC 板中负折射的观察，其中垂直引导是由连续介质中的束缚态实现的，并且基本上超出了光锥。这种异常折射和引导机制是基于空间色散的同步制作和辐射连续谱内布洛赫模式的辐射寿命。提供微波实验以进一步验证全介电 PhC 平台中的数值方案。