Low‐Loss Anisotropic Image Polaritons in van der Waals Crystal α‐MoO3

Orthorhombic molybdenum trioxide (α‐MoO3), a newly discovered polaritonic van der Waals crystal, is attracting significant attention due to its strongly anisotropic mid‐infrared phonon‐polaritons. At the same time, coupling of polariton with its mirror image in an adjacent metal gives rise to a sign...

Full description

Saved in:
Bibliographic Details
Published in:Advanced optical materials 2022-11, Vol.10 (21), p.n/a
Main Authors: Menabde, Sergey G., Jahng, Junghoon, Boroviks, Sergejs, Ahn, Jongtae, Heiden, Jacob T., Hwang, Do Kyung, Lee, Eun Sung, Mortensen, N. Asger, Jang, Min Seok
Format: Article
Language:English
Subjects:
Crystallography
Damping
Group velocity
Image manipulation
image polaritons
Infrared imagery
Materials science
Molybdenum trioxide
Momentum
Optics
Phonons
phonon‐polaritons
Polaritons
Substrates
van der Waals crystals
Wave propagation
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Orthorhombic molybdenum trioxide (α‐MoO3), a newly discovered polaritonic van der Waals crystal, is attracting significant attention due to its strongly anisotropic mid‐infrared phonon‐polaritons. At the same time, coupling of polariton with its mirror image in an adjacent metal gives rise to a significantly more confined image mode. Here, monocrystalline gold flakes—an atomically flat low‐loss substrate for mid‐infrared image polaritons—are employed to measure the full complex‐valued propagation constant of the hyperbolic image phonon‐polaritons in α‐MoO3 by near‐field probing. The anisotropic dispersion is mapped and the damping of the polaritons propagating at different angles to the crystallographic directions of α‐MoO3 is analyzed. These experiments demonstrate the strongly confined image phonon‐polaritons in α‐MoO3 exhibiting intrinsic limiting lifetime of 4.2 ps and a propagation length of 4.5 times the polariton wavelength, owing to the negligible substrate‐mediated loss. Furthermore, it is shown that the image modes with positive group velocity have simultaneously larger momentum and lifetime compared to their counterparts on a dielectric substrate, while the image modes with negative group velocity possess a smaller momentum. These results spotlight the hyperbolic image phonon‐polaritons as a superior platform for unconventional light manipulation at the nanoscale. Hyperbolic image phonon‐polaritons in α‐MoO3 on monocrystalline gold demonstrate simultaneously longer lifetime and larger field compression, providing a new platform for light manipulation at nanoscale. Besides, monocrystalline gold flakes are demonstrated to be a superior substrate for near‐field studies of phonon‐polaritons in van der Waals crystals.
ISSN:2195-1071
2195-1071
DOI:10.1002/adom.202201492