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Hyperbolic phonon-polaritons in boron nitride for near-field optical imaging and focusing

2015; Nature Portfolio; Volume: 6; Issue: 1 Linguagem: Inglês

10.1038/ncomms8507

2041-1723

Peining Li, Martin Lewin, Andrey V. Kretinin, Joshua D. Caldwell, Kostya S. Novoselov, Takashi Taniguchi, Kenji Watanabe, Fabian Gaußmann, Thomas Taubner,

Metamaterials and Metasurfaces Applications

Optical imaging beyond the diffraction limit was one of the primary motivations for negative-index metamaterials, resulting in Pendry's perfect lens and the more attainable superlens. While these approaches offer sub-diffractional resolution, they do not provide a mechanism for magnification of the image. Hyperbolic (or indefinite-permittivity) metamaterials have been theoretically considered and experimentally demonstrated to provide simultaneously subdiffractive imaging and magnification; however, they are plagued with low efficiency and complex fabrication. In this work, we present theoretical and experimental studies of near-field optical imaging through a flat slab of the low-loss, natural hyperbolic material, hexagonal boron nitride (hBN). This thin hBN layer exhibits wavelength-dependent multifunctional operations, offering both an enhanced near-field imaging of single buried objects with down to lambda/32 resolution (0.4 um at lambda=12.8 um), as well as enabling an enlarged reconstruction of the geometric outline of the investigated objects. Both the excellent resolution and the multifunctional operation can be explained based on the volume-confined, wavelength-dependent propagation angle of Type I hyperbolic polaritons. Our results provide both the understanding of near-field imaging performance through this natural hyperbolic media, as well as inspire their exciting potential for guiding and sensing of light at an extreme sub-diffractional scale.