Ultrafast Nano-imaging and Optical Control of Hyperbolic Phonon Polaritons at hBN/WS₂ Heterojunctions.

Authors

Kazuki Kamada, Keisuke Shinokita, Fanyu Zeng, Ryo Kitaura, Kenji Watanabe, Takashi Taniguchi, Alexander Paarmann, Masahiro Shibuta, Takashi Kumagai, Jun Nishida

Published in

Nano letters. Jul 27, 2026. Epub Jul 27, 2026.

Abstract

Manipulating nanoscale light-matter interactions on ultrafast time scales is indispensable for future polaritonic devices. Hyperbolic phonon polaritons (HPhPs) in van der Waals materials enable deep subwavelength confinement of electromagnetic fields in the infrared region and long-distance propagation of polaritonic waves. However, achieving ultrafast imaging and optical control of HPhPs remains a major challenge. Here, we demonstrate the direct observation of transient modulation of HPhPs induced by local photocarrier generation in WS₂hBN heterostructures using ultrafast infrared scanning near-field optical microscopy. We implement grating-based spectral filtering of broadband near-field scattering to simultaneously achieve nanoscale and femtosecond spatiotemporal resolution together with fine spectral selectivity. This ultrafast nano-imaging technique reveals that photocarriers in WS₂ modulate the polaritonic field amplitudes and wavelengths of HPhPs in hBN. Theoretical simulations corroborate that these changes arise from photoinduced changes in WS₂ dielectric properties. This approach offers a versatile platform for exploring ultrafast polaritonic dynamics at the nanoscale.

PMID:
42504570
Bibliographic data and abstract were imported from PubMed on 27 Jul 2026.

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