Hyperbolic metamaterials (HMMs) are anisotropic optical materials supporting highly confined propagating electromagnetic modes. However, it is challenging to tailor and excite these modes at optical frequencies by prism coupling because of the unavailability of high refractive index prisms for matching the momentum between the incident light and the guided modes. Here, we report on the mechanism of excitation of high-index Bloch plasmon polariton modes with sub-diffraction spatial confinement using a meta-grating, which is a combined structure of a metallic diffraction grating and a type II HMM. We show how a one-dimensional plasmonic grating without any mode in the infrared spectral range, if coupled to an HMM supporting high-index modes, can efficiently enable the excitation of these modes via coupling to far-field radiation. Our theoretical predictions are confirmed by experimental reflection measurements as a function of angle of incidence and excitation wavelength. We introduce design principles to achieve a full control of high-index modes in meta-gratings, thus enabling a better understanding of light–matter interaction in this type of hybrid structure. The exploitation of the spectral response of these modes can find applications in bio-chemical sensing, integrated optics, and optical sub-wavelength imaging.

中文翻译：

---

光栅耦合双曲超材料中的Designer Bloch等离子体激元极化子色散

双曲超材料（HMM）是各向异性光学材料，支持高度受限的传播电磁模式。然而，由于无法利用高折射率棱镜来匹配入射光和引导模之间的动量，因此通过棱镜耦合在光频率下定制和激发这些模具有挑战性。在这里，我们报告了使用亚光栅将高折射率布洛赫等离子体激元极化子模式激发与亚衍射空间限制的机制，亚光栅是金属衍射光栅和II型HMM的组合结构。我们展示了如果在红外光谱范围内没有任何模式的一维等离激元光栅，如果耦合到支持高折射率模式的HMM，如何通过耦合到远场辐射有效地激发这些模式。我们的理论预测通过实验反射测量作为入射角和激发波长的函数得到证实。我们介绍了设计原理，以实现对元光栅中高折射率模式的完全控制，从而使人们能够更好地理解这种混合结构中的光-物质相互作用。利用这些模式的光谱响应可以在生物化学传感，集成光学和光学亚波长成像中找到应用。