Dynamic wavefront shaping with optical metasurfaces has presented a major challenge and inspired a large number of highly elaborate solutions. Here, this study experimentally demonstrates thermo‐optically reconfigurable, nonlocal metasurfaces using simple device architectures and conventional CMOS‐compatible dielectric materials. These metasurfaces support quasi‐bound states in the continuum (q‐BICs) derived from symmetry breaking and encoded with a spatially varying geometric phase, such that they shape optical wavefront exclusively on spectrally narrowband resonances. Due to the enhanced light‐matter interaction enabled by the resonant q‐BICs, a slight variation of the refractive index introduced by heating and cooling the entire device leads to a substantial shift of the resonant wavelength and a subsequent change to the optical wavefront associated with the resonance. This study experimentally demonstrates a metalens modulator, the focusing capability of which can be thermally turned on and off, and reconfigurable metalenses, which can be thermo‐optically switched to produce two distinct focal patterns. The devices offer a pathway to realize reconfigurable, multifunctional meta‐optics using established manufacturing processes and widely available dielectric materials that are conventionally not considered “active” materials due to their small thermo‐optic or electro‐optic coefficients.
- PAR ID:
- 10228877
- Date Published:
- Journal Name:
- Nanophotonics
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2192-8606
- Page Range / eLocation ID:
- 655 to 665
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Photonic devices rarely provide both elaborate spatial control and sharp spectral control over an incoming wavefront. In optical metasurfaces, for example, the localized modes of individual meta-units govern the wavefront shape over a broad bandwidth, while nonlocal lattice modes extended over many unit cells support high quality-factor resonances. Here, we experimentally demonstrate nonlocal dielectric metasurfaces in the near-infrared that offer both spatial and spectral control of light, realizing metalenses focusing light exclusively over a narrowband resonance while leaving off-resonant frequencies unaffected. Our devices attain this functionality by supporting a quasi-bound state in the continuum encoded with a spatially varying geometric phase. We leverage this capability to experimentally realize a versatile platform for multispectral wavefront shaping where a stack of metasurfaces, each supporting multiple independently controlled quasi-bound states in the continuum, molds the optical wavefront distinctively at multiple wavelengths and yet stay transparent over the rest of the spectrum. Such a platform is scalable to the visible for applications in augmented reality and transparent displays.
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1515/nanoph-2020-0375
