Near-zero-index platforms arise as a new opportunity for light manipulation with boosting of optical nonlinearities, transmission properties in waveguides, and constant phase distribution. In addition, they represent a solution to impedance mismatch faced in photonic circuitry offering several applications in quantum photonics, communication, and sensing. However, their realization is limited to the availability of materials that could exhibit such low index. For materials used in the visible and near-infrared wavelengths, the intrinsic losses annihilate most of near-zero index properties. The design of all-dielectric photonic crystals with specific electromagnetic modes overcomes the issue of intrinsic losses while showing effective mode index near zero. Nonetheless, these modes strongly radiate to the surrounding environment, greatly limiting the devices applications. Here, a novel all-dielectric photonic crystal structure is explored that is able to sustain effective near-zero-index modes coupled to directive bound-states in the continuum in order to decrease radiative losses, opening extraordinary opportunities for radiation manipulation in nanophotonic circuits. Moreover, its relatively simple design and phase stability facilitate integration and reproducibility with other photonic components.

中文翻译：

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在连续介质中具有定向束缚态的近零折射率光子晶体

近零指数平台作为光操纵的新机会出现，可提高光学非线性、波导中的传输特性和恒定相位分布。此外，它们代表了光子电路中阻抗失配的解决方案，提供了量子光子学、通信和传感方面的多种应用。然而，它们的实现仅限于可能表现出如此低指数的材料的可用性。对于在可见光和近红外波长中使用的材料，固有损耗消除了大部分近零指数特性。具有特定电磁模式的全介电光子晶体的设计克服了固有损耗的问题，同时显示出接近零的有效模式指数。尽管如此，这些模式强烈地辐射到周围环境，极大地限制了设备的应用。在这里，探索了一种新型的全介电光子晶体结构，该结构能够维持有效的近零折射率模式，与连续介质中的定向束缚态耦合，以减少辐射损失，为纳米光子电路中的辐射操纵开辟了非凡的机会。此外，其相对简单的设计和相位稳定性有助于与其他光子组件的集成和再现性。