Misalignment between the Directions of Propagation and Decay of Nanoscale-confined Polaritons

Abstract

Anisotropic van der Waals crystals have gained significant attention in nanooptics and optoelectronics due to their unconventional optical properties, including anomalous reflection, canalization, and nanofocusing. Polaritons -- light coupled to matter excitations -- govern these effects, with their complex wavevector encoding key parameters such as wavelength, lifetime, field confinement, and propagation direction. However, determining the complex wavevector, particularly the misalignment between its real and imaginary parts, has remained a challenge due to the complexity of the dispersion relation. Here, using near-field nanoimaging, we introduce a self-consistent method to extract the complex wavevector from polaritonic near-field images. We experimentally reveal a strong misalignment between the real and imaginary components of the wavevector, significantly impacting the interpretation of near-field experiments. Our findings establish a new paradigm for optical nanoimaging, providing a robust framework for accurately extracting polariton parameters and advancing the broader field of nanooptics of lossy anisotropic crystals.

arXiv comment19 pages, 4 figures, to be published in Nano Letters

References in corpus (15)

• Gate-tuning of graphene plasmons revealed by infrared nano-imaging
• Optical nano-imaging of gate-tuneable graphene plasmons
• Polaritons in layered 2D materials
• Highly confined low-loss plasmons in graphene-boron nitride heterostructures
• Observation of topological polaritons and photonic magic angles in twisted van der Waals bi-layers
• Configure polaritons in twisted $\alpha$-MoO3
• Broad Spectral Tuning of Ultra-Low Loss Polaritons in a van der Waals Crystal by Intercalation
• Twisted Nano-optics: Manipulating Light at the Nanoscale with Twisted Phonon Polaritonic Slabs
• Infrared permittivity of the biaxial van der Waals semiconductor $\alpha$-MoO${}_3$ from near- and far-field correlative studies
• Van der Waals thin films of WTe2 for natural hyperbolic plasmonic surfaces
• Analytical approximations for the dispersion of electromagnetic modes in slabs of biaxial crystals
• Nanoscale-confined Terahertz Polaritons in a van der Waals Crystal
• Multiple and spectrally robust photonic magic angles in reconfigurable α-MoO3 trilayers
• Enabling propagation of anisotropic polaritons along forbidden directions via a topological transition
• Active tuning of highly anisotropic phonon polaritons in van der Waals crystal slabs by gated graphene

Cited by in corpus (1)

• Long-range mid-infrared energy transfer mediated by hyperbolic phonon polaritons