Continuous angle-tunable birefringence with freeform metasurfaces for arbitrary polarization conversion

Zhujun Shi, Alexander Y. Zhu, Zhaoyi Li, Yao-Wei Huang, Wei Ting Chen, Cheng-Wei Qiu, Federico Capasso*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    13 Scopus citations


    Birefringence occurs when light with different polarizations sees different refractive indices during propagation. It plays an important role in optics and has enabled essential polarization elements such as wave plates. In bulk crystals, it is typically constrained to linear birefringence. In metamaterials with freeform meta-atoms, however, one can engineer the optical anisotropy such that light sees different indices for arbitrary-linear, circular, or elliptical-orthogonal eigen-polarization states. Using topology-optimized metasurfaces, we demonstrate this arbitrary birefringence. It has the unique feature that it can be continuously tuned from linear to elliptical birefringence, by changing the angle of incidence. In this way, a single metasurface can operate as many wave plates in parallel, implementing different polarization transformations. Angle-tunable arbitrary birefringence expands the scope of polarization optics, enables compact and versatile polarization operations that would otherwise require cascading multiple elements, and may find applications in polarization imaging, quantum optics, and other areas.

    Original languageEnglish
    Article number3367
    Number of pages7
    JournalScience Advances
    Issue number23
    StatePublished - 3 Jun 2020


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