Ultralow-loss polaritons in isotopically pure boron nitride


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.

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Figure 1: Influence of isotopic enrichment on hBN optic phonons.
Figure 2: Influence of isotopic enrichment on hBN dielectric function.
Figure 3: Measuring polariton propagation as a function of isotopic enrichment.
Figure 4: Dispersion of hyperbolic phonon polaritons in isotopically enriched hBN.
Figure 5: Quantifying improvements in loss with isotopic enrichments.


  1. 1

    Yu, N. & Capasso, F. Flat optics with designer metasurfaces. Nat. Mater. 13, 139–150 (2014).

    CAS  Article  Google Scholar 

  2. 2

    Kildishev, A. V., Boltasseva, A. & Shalaev, V. M. Planar photonics with metasurfaces. Science 339, 1232009 (2013).

    Article  Google Scholar 

  3. 3

    Li, P. et al. Reversible optical switching of highly confined phonon polaritons with an ultrathin phase-change material. Nat. Mater. 15, 870–875 (2016).

    CAS  Article  Google Scholar 

  4. 4

    Chen, J. et al. Optical nano-imaging of gate-tunable graphene plasmons. Nature 487, 77–81 (2012).

    CAS  Article  Google Scholar 

  5. 5

    Fei, Z. et al. Gate-tuning of graphene plasmons revealed by infrared nano-imaging. Nature 487, 82–85 (2012).

    CAS  Article  Google Scholar 

  6. 6

    Dai, S. et al. Graphene on hexagonal boron nitride as an tunable hyperbolic metamaterial. Nat. Nanotech. 10, 682–686 (2015).

    CAS  Article  Google Scholar 

  7. 7

    Caldwell, J. D. et al. Atomic-scale photonic hybrids for mid-infrared and terahertz nanophotonics. Nat. Nanotech. 11, 9–15 (2016).

    CAS  Article  Google Scholar 

  8. 8

    Spann, B. T. et al. Photoinduced tunability of the reststrahlen band in 4H-SiC. Phys. Rev. B 93, 085205 (2016).

    Article  Google Scholar 

  9. 9

    Khurgin, J. B. How to deal with the loss in plasmonics and metamaterials. Nat. Nanotech. 10, 2–6 (2014).

    Article  Google Scholar 

  10. 10

    Caldwell, J. D. et al. Low-loss, infrared and terahertz nanophotonics with surface phonon polaritons. Nanophotonics 4, 44–68 (2015).

    CAS  Article  Google Scholar 

  11. 11

    Caldwell, J. D. et al. Low-loss, extreme sub-diffraction photon confinement via silicon carbide surface phonon polariton nanopillar resonators. Nano Lett. 13, 3690–3697 (2013).

    CAS  Article  Google Scholar 

  12. 12

    Caldwell, J. D. et al. Sub-diffractional, volume-confined polaritons in the natural hyperbolic material hexagonal boron nitride. Nat. Commun. 5, 5221 (2014).

    CAS  Article  Google Scholar 

  13. 13

    Wang, T., Li, P., Hauer, B., Chigrin, D. N. & Taubner, T. Optical properties of single infrared resonant circular microcavities for surface phonon polaritons. Nano Lett. 13, 5051–5055 (2013).

    CAS  Article  Google Scholar 

  14. 14

    Low, T. et al. Polaritons in layered two-dimensional materials. Nat. Mater. 16, 182–194 (2017).

    CAS  Article  Google Scholar 

  15. 15

    Basov, D. N., Fogler, M. M. & Garcia de Abajo, F. J. Polaritons in van der Waals materials. Science 354, 195–203 (2016).

    CAS  Article  Google Scholar 

  16. 16

    Wang, T. et al. Phononic bowtie nanoantennas: controlling ultra-narrow-band infrared thermal radiation at the nanoscale. ACS Photon. 4, 1753–1760 (2015).

    CAS  Article  Google Scholar 

  17. 17

    Yoxall, E. et al. Direct observation of ultraslow hyperbolic polariton propagation with negative phase velocity. Nat. Photon. 9, 674–678 (2015).

    CAS  Article  Google Scholar 

  18. 18

    Cardona, M. & Thewalt, M. L. W. Isotope effects on the optical spectra of semiconductors. Rev. Mod. Phys. 77, 1173–1224 (2005).

    CAS  Article  Google Scholar 

  19. 19

    Khurgin, J. B., Jena, D. & Ding, Y. J. Isotope disorder of phonons in GaN and its beneficial effect on high power field effect transistors. Appl. Phys. Lett. 93, 032110 (2008).

    Article  Google Scholar 

  20. 20

    Dai, S. et al. Subdiffractional focusing and guiding of polaritonic rays in a natural hyperbolic material. Nat. Commun. 6, 6963 (2015).

    CAS  Article  Google Scholar 

  21. 21

    Liu, Z., Lee, H., Xiong, Y., Sun, C. & Zhang, X. Far-field optical hyperlens magnifying sub-diffraction limited objects. Science 315, 1686 (2007).

    CAS  Article  Google Scholar 

  22. 22

    Xiong, Y., Liu, Z. & Zhang, X. A simple design of flat hyperlens for lithography and imaging with half-pitch resolution down to 20 nm. Appl. Phys. Lett. 94, 203108 (2009).

    Article  Google Scholar 

  23. 23

    Kumar, A., Low, T., Fung, K. H., Avouris, P. & Fang, N. X. Tunable light-matter interaction and the role of hyperbolicity in graphene-hBN system. Nano Lett. 15, 3172–3180 (2015).

    CAS  Article  Google Scholar 

  24. 24

    Dai, S. et al. Tunable phonon polaritons in atomically thin van der Waals crystals of boron nitride. Science 343, 1125–1129 (2014).

    CAS  Article  Google Scholar 

  25. 25

    Giles, A. J. et al. Imaging of anomalous internal reflections of hyperbolic phonon-polaritons in hexagonal boron nitride. Nano Lett. 16, 3858–3865 (2016).

    CAS  Article  Google Scholar 

  26. 26

    Poddubny, A., Iorsh, I., Belov, P. & Kivshar, Y. Hyperbolic metamaterials. Nat. Photon. 7, 948–957 (2013).

    CAS  Article  Google Scholar 

  27. 27

    Kubota, Y., Watanabe, K., Tsuda, O. & Taniguchi, T. Deep ultraviolet light-emitting hexagonal boron nitride synthesized at atmospheric pressure. Science 317, 932–934 (2007).

    CAS  Article  Google Scholar 

  28. 28

    Hoffmann, T. B., Zhang, Y., Edgar, J. H. & Gaskill, D. K. Growth of hBN using metallic boron: isotopically enriched h10BN and h11BN. MRS Proc. 1635, 35–40 (2014).

    Article  Google Scholar 

  29. 29

    Zhang, J. M. et al. Raman spectra of isotopic GaN. Phys. Rev. B 56, 14399–14406 (1997).

    CAS  Article  Google Scholar 

  30. 30

    Rohmfeld, S., Hundhausen, M., Ley, L., Schulze, N. & Pensl, G. Isotope-disorder-induced line broadening of phonons in the Raman spectra of SiC. Phys. Rev. Lett. 86, 826–829 (2001).

    CAS  Article  Google Scholar 

  31. 31

    Lindsay, L., Broido, D. A. & Reinecke, T. L. Ab-initio thermal transport in compound semiconductors. Phys. Rev. B 87, 165201 (2013).

    Article  Google Scholar 

  32. 32

    Lindsay, L., Broido, D. A. & Reinecke, T. L. Phonon-isotope scattering and thermal conductivity in materials with a large isotope effect: a first-principles study. Phys. Rev. B 88, 144306 (2013).

    Article  Google Scholar 

  33. 33

    Caldwell, J. D. & Novoselov, K. S. van der Waals heterostructures: mid-infrared nanophotonics. Nat. Mater. 14, 364–366 (2015).

    CAS  Article  Google Scholar 

  34. 34

    Woessner, A. et al. Highly confined low-loss plasmons in graphene–boron nitride heterostructures. Nat. Mater. 14, 421–425 (2015).

    CAS  Article  Google Scholar 

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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).

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The concept for the experiment was initially developed by J.D.C., A.J.G., T.L.R. and I.V. All hBN crystals were grown by T.H. and S.L. under the direction of J.E. and provided to J.D.C. through an amazing stroke of good fortune. Exfoliation of hBN flakes was performed by J.D.C. and A.J.G., while AFM characterization was provided by A.J.G. Raman and FTIR analysis was provided by J.D.C., A.J.G., N.A., I.C., C.T.E. and J.G.T. Theoretical calculations of the phonon lifetimes were performed by L.L. and T.L.R., while the code for calculating the dispersion relationship of the HPhPs in hBN was developed by M.F. The FFTs and corresponding lineshape fits were created by I.V. s-SNOM measurements were performed within the lab of D.N.B. by A.J.G. and S.D. All authors discussed results at all stages and participated in the development of the manuscript. A.J.G. and J.D.C. wrote the paper.

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Correspondence to Alexander J. Giles.

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Giles, A., Dai, S., Vurgaftman, I. et al. Ultralow-loss polaritons in isotopically pure boron nitride. Nature Mater 17, 134–139 (2018). https://doi.org/10.1038/nmat5047

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