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Polaritons in two-dimensional materials provide extreme light confinement that is difficult to achieve with metal plasmonics. However, such tight confinement inevitably increases optical losses through various damping channels. Here we demonstrate that hyperbolic phonon polaritons in hexagonal boron nitride can overcome this fundamental trade-off. Among two observed polariton modes, featuring a symmetric and antisymmetric charge distribution, the latter exhibits lower optical losses and tighter polariton confinement. Far-field excitation and detection of this high-momenta mode become possible with our resonator design that can boost the coupling efficiency via virtual polariton modes with image charges that we dub ‘image polaritons’. Using these image polaritons, we experimentally observe a record-high effective index of up to 132 and quality factors as high as 501. Further, our phenomenological theory suggests an important role of hyperbolic surface scattering in the damping process of hyperbolic phonon polaritons.
Bibliographical noteFunding Information:
This research was supported by grants from the National Science Foundation (NSF) MRSEC Seed (to I.-H.L., T.L., and S.-H.O.), NSF ECCS Award #1809723 (to I.-H.L., S.-H.O., and T.L.), and the Samsung Global Research Outreach (GRO) Program (to S.-H.O.). Funding for J.D.C. and M.H. was provided by the Office of Naval Research under grant number N000141812107. X.Z., Y.L., and K.W. were supported in part by NSF DMREF Award #1922165. J.H.E. and S.L. were supported by the Materials Engineering and Processing program of the NSF (CMMI 1538127) and the II−VI Foundation for hBN crystal growth. S.-H.O. further acknowledges support from the Sanford P. Bordeau chair at the University of Minnesota. Device fabrication was performed in the Minnesota Nano Center at the University of Minnesota, which is supported by the NSF through the National Nanotechnology Coordinated Infrastructure (NNCI) under Award # ECCS-1542202. Electron microscopy measurements were performed in the Characterization Facility, which has received capital equipment from the NSF MRSEC.
How much support was provided by MRSEC?
Reporting period for MRSEC
- Period 7
PubMed: MeSH publication types
- Journal Article