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Optical Imaging of Ultrafast Phonon-Polariton Propagation through an Excitonic Sensor
journal contribution
posted on 2023-10-18, 22:16 authored by Shan-Wen Cheng, Ding Xu, Haowen Su, James M. Baxter, Luke N. Holtzman, Kenji Watanabe, Takashi Taniguchi, James C. Hone, Katayun Barmak, Milan DelorHexagonal boron nitride (hBN) hosts phonon polaritons
(PhP), hybrid
light–matter states that facilitate electromagnetic field confinement
and exhibit long-range ballistic transport. Extracting the spatiotemporal
dynamics of PhPs usually requires “tour de force” experimental
methods such as ultrafast near-field infrared microscopy. Here, we
leverage the remarkable environmental sensitivity of excitons in two-dimensional
transition metal dichalcogenides to image PhP propagation in adjacent
hBN slabs. Using ultrafast optical microscopy on monolayer WSe2/hBN heterostructures, we image propagating PhPs from 3.5
K to room temperature with subpicosecond and few-nanometer precision.
Excitons in WSe2 act as transducers between visible light
pulses and infrared PhPs, enabling visible-light imaging of PhP transport
with far-field microscopy. We also report evidence of excitons in
WSe2 copropagating with hBN PhPs over several micrometers.
Our results provide new avenues for imaging polar excitations over
a large frequency range with extreme spatiotemporal precision and
new mechanisms to realize ballistic exciton transport at room temperature.
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remarkable environmental sensitivitylarge frequency rangealso report evidencerange ballistic transporthosts phonon polaritonsimaging polar excitationsimage propagating phpsvisible light pulsesimage php propagationextreme spatiotemporal precisionadjacent hbn slabs2 subfield infrared microscopyphp transportfield microscopylight imaginginfrared phpsultrafast phononspatiotemporal dynamicspolariton propagationnanometer precisionenabling visibleoptical imaginghbn phpsultrafast nearseveral micrometersroom temperaturenew mechanismsexhibit long5 k