Marcucci Niccolò, Giordano Maria Caterina, Zambito Giorgio, Troia Adriano, Buatier de Mongeot Francesco, Descrovi Emiliano
Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 10129, Italy.
Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, Genova, 16146, Italy.
Nanophotonics. 2023 Feb 20;12(6):1091-1104. doi: 10.1515/nanoph-2022-0609. eCollection 2023 Mar.
Fostered by the recent advancements in photonic technologies, the need for all-optical dynamic control on complex photonic elements is emerging as more and more relevant, especially in integrated photonics and metasurface-based flat-optics. In this framework, optically-induced anisotropy has been proposed as powerful mean enabling tuning functionalities in several planar architectures. Here, we design and fabricate an anisotropic two-dimensional bull's eye cavity inscribed within an optically-active polymeric film spun on a one-dimensional photonic crystal sustaining Bloch surface waves (BSW). Thanks to the cavity morphology, two surface resonant modes with substantially orthogonal polarizations can be coupled within the cavity from free-space illumination. We demonstrate that a dynamic control on the resonant mode energies can be easily operated by modulating the orientation of the optically-induced birefringence on the surface, via a polarized external laser beam. Overall, reversible blue- and red-shifts of the resonant BSWs are observed within a spectral range of about 2 nm, with a moderate laser power illumination. The polymeric structure is constituted by a novel blend of an azopolymer and a thermally-sensitive resist, which allows a precise patterning via thermal scanning probe lithography, while providing a significant structural integrity against photo-fluidization or mass-flow effects commonly occurring in irradiated azopolymers. The proposed approach based on tailored birefringence opens up new pathways to finely control the optical coupling of localized surface modes to/from free-space radiation, particularly in hybrid organic-inorganic devices.
在光子技术最近取得的进展的推动下，对复杂光子元件进行全光动态控制的需求变得越来越重要，尤其是在集成光子学和基于超表面的平面光学领域。在此框架下，光致各向异性已被提议作为一种强大的手段，可在多种平面结构中实现调谐功能。在这里，我们设计并制造了一种各向异性二维靶心腔，该腔刻写在旋涂于一维光子晶体上的光学活性聚合物薄膜内，该光子晶体支持布洛赫表面波（BSW）。由于腔的形态，具有基本正交偏振的两个表面共振模式可以通过自由空间照明在腔内耦合。我们证明，通过偏振外部激光束调制表面光致双折射的取向，可以轻松地对共振模式能量进行动态控制。总体而言，在约2nm的光谱范围内，在适度的激光功率照明下，观察到共振BSW的可逆蓝移和红移。该聚合物结构由一种新型的偶氮聚合物和热敏抗蚀剂混合物构成，它允许通过热扫描探针光刻进行精确图案化，同时提供显著的结构完整性，以抵抗辐照偶氮聚合物中常见的光流化或质量流效应。基于定制双折射提出的方法为精细控制局域表面模式与自由空间辐射之间的光耦合开辟了新途径，特别是在混合有机-无机器件中。
