Abstract
Polaritonic materials that support epsilon-near-zero (ENZ) modes offer the opportunity to design light-matter interactions at the nanoscale through extreme subwavelength light confinement, producing phenomena like resonant perfect absorption. However, the utility of ENZ modes in nanophotonic applications has been limited by a flat spectral dispersion, which leads to small group velocities and extremely short propagation lengths. Here, we overcome this constraint by hybridizing ENZ and surface plasmon polariton (SPP) modes in doped cadmium oxide epitaxial bilayers. This results in strongly coupled hybrid modes that are characterized by an anticrossing in the polariton dispersion and a large spectral splitting on the order of 1/3 of the mode frequency. These hybrid modes simultaneously achieve modal propagation and ENZ mode-like interior field confinement, adding propagation character to ENZ mode properties. We subsequently tune the resonant frequencies, dispersion, and coupling of these polaritonic-hybrid-epsilon-near-zero (PH-ENZ) modes by tailoring the modal oscillator strength and the ENZ-SPP spectral overlap. PH-ENZ modes ultimately leverage the most desirable characteristics of both ENZ and SPP modes, allowing us to overcome the canonical plasmonic trade-off between confinement and propagation length.
| Original language | English |
|---|---|
| Pages (from-to) | 948-957 |
| Number of pages | 10 |
| Journal | Nano Letters |
| Volume | 19 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 13 2019 |
| Externally published | Yes |
Funding
We gratefully acknowledge support for this work by NSF Grant CHE-1507947, by Army Research Office Grants W911NF-16-1-0406 and W911NF-16-1-0037, and by Office of Naval Research Grant N00014-18-12107. T.G.F. and J.D.C. both acknowledge support from Vanderbilt School of Engineering through the latter’s startup funding package. N.E. acknowledges the partial support from the Vannevar Bush Faculty Fellowship program sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineering and funded by the Office of Naval Research through Grant N00014-16-1-2029. In addition, this work was performed in part at the Analytical Instrumentation Facility (AIF), which is supported by the State of North Carolina and the National Science Foundation (award number ECCS-1542015). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI). We additionally thank the Efimenko and Genzer groups (NCSU, CBE) for providing use of their IR-VASE and would also like to acknowledge Andrew Klump for performing ToF-SIMS measurements.
| Funders | Funder number |
|---|---|
| Vanderbilt School of Engineering | |
| National Science Foundation | ECCS-1542015, CHE-1507947 |
| National Science Foundation | |
| Office of Naval Research | N00014-18-12107 |
| Office of Naval Research | |
| Army Research Office | W911NF-16-1-0037, W911NF-16-1-0406 |
| Army Research Office | |
| Office of the Assistant Secretary for Research and Technology | N00014-16-1-2029 |
| Office of the Assistant Secretary for Research and Technology |
Keywords
- Epsilon-near-zero
- epitaxy
- infrared
- mode confinement
- nanophotonics
- strong coupling
- surface plasmon