Conventional optical components are limited to size scales much larger than the wavelength of light, as changes to the amplitude, phase and polarization of the electromagnetic fields are accrued gradually along an optical path. However, advances in nanophotonics have produced ultrathin, so-called ‘flat’ optical components that beget abrupt changes in these properties over distances significantly shorter than the free-space wavelength1,2,3,4,5,6,7,8. Although high optical losses still plague many approaches9, phonon polariton (PhP) materials have demonstrated long lifetimes for sub-diffractional modes10,11,12,13 in comparison to plasmon-polariton-based nanophotonics. We experimentally observe a threefold improvement in polariton lifetime through isotopic enrichment of hexagonal boron nitride (hBN). Commensurate increases in the polariton propagation length are demonstrated via direct imaging of polaritonic standing waves by means of infrared nano-optics. Our results provide the foundation for a materials-growth-directed approach aimed at realizing the loss control necessary for the development of PhP-based nanophotonic devices.
A.J.G. and C.T.E. acknowledge support from the National Research Council (NRC) and I.C. acknowledges support from the American Society of Engineering (ASEE) NRL Postdoctoral Fellowship Programs. Funding for N.A. was provided through the Naval Research Enterprise Internship Program (NREIP) and is currently an undergraduate student at Rice University in Houston, Texas. Funding for J.D.C., I.V., J.G.T. and T.L.R. was provided by the Office of Naval Research and distributed by the Nanoscience Institute at the Naval Research Laboratory. Development of the instrumentation is supported by ARO w911NF-13-1-0210 and AFOSR FA9550-15-0478. D.N.B. is the Moore Investigator in Quantum Materials EPIQS program GBMF4533. D.N.B, M.M.F. and S.D. acknowledge support from ONR N00014-15-1-2671. The hBN crystal growth at Kansas State University was supported by NSF grant CMMI 1538127. L.L. acknowledges support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division. SIMS measurements and analysis was provided by Evans Analytical Group as part of a work-for-hire agreement. The authors express their thanks to K. Wahl for use of her Raman microscope. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide licence to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).