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Broadband depolarized perfect Littrow diffraction with multilayer freeform metagratingsстатья
Статья опубликована в высокорейтинговом журнале
Статья опубликована в журнале из списка Web of Science и/или Scopus- Авторы: Dong Siyu, Zhanyi Zhang, Lingyun Xie, Jingyuan Zhu, Haigang Liang, Zeyong Wei, Yuzhi Shi, Alexander Tikhonravov, Zhanshan Wang, Lei Zhou, Xinbin Cheng
- Журнал: Optica
- Том: 10
- Номер: 5
- Год издания: 2023
- Издательство: OSA - The Optical Society
- Местоположение издательства: США
- Первая страница: 585
- Последняя страница: 585
- DOI: 10.1364/optica.486332
- Аннотация: Littrow diffraction, the ability to reflect light back along incident direction, is a key functionality of retroreflectors, exhibiting wide applications in nanophotonics. However, retroreflectors have hitherto low working efficiencies and narrow bandwidths, and work only for a specific polarization, being unfavorable for integration-optics applications. Here, we propose a type of metagrating consisting of an all-dielectric Bragg reflector and a periodic metasurface with freeform-shaped dielectric resonators, which enables broadband depolarized perfect Littrow diffraction at optical frequencies. The physics is governed by exact cancellations of specular reflections contributed by two Bragg modes in metagratings, enabled by careful structural optimization to yield the desired reflection-phase difference of Bragg modes within a wide frequency band and for two polarizations. As a proof of concept, we experimentally demonstrate retroreflections with unpolarized absolute efficiency higher than 98% (99% in design) at 1030–1090 nm using multilayer freeform metagratings. Our results pave the way for numerous applications based on high-efficiency Littrow diffraction (e.g., spectral laser beam combining), which is not bonded to a specific polarization or frequency.
- Добавил в систему: Тихонравов Александр Владимирович