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Mid-infrared radiative emission from bright hot plasmons in graphene


Carrier excitation and decay processes in graphene are of broad interest since relaxation pathways that are not present in conventional materials are enabled by a gapless Dirac electronic band structure. Here, we report that a previously unobserved decay pathway—hot plasmon emission—results in Fermi-level-dependent mid-infrared emission in graphene. Our observations of non-thermal contributions to Fermi-level-dependent radiation are an experimental demonstration of hot plasmon emission arising from a photo-inverted carrier distribution in graphene achieved via ultrafast optical excitation. Our calculations indicate that the reported plasmon emission process can be several orders of magnitude brighter than Planckian emission mechanisms in the mid-infrared spectral range. Both the use of gold nanodisks to promote scattering and localized plasmon excitation and polarization-dependent excitation measurements provide further evidence for bright hot plasmon emission. These findings define an approach for future work on ultrafast and ultrabright graphene emission processes and mid-infrared light source applications.

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Fig. 1: Carrier relaxation processes in graphene and experimental configuration.
Fig. 2: Fermi-level-dependent emission spectra in planar graphene.
Fig. 3: Non-equilibrium graphene plasmon dispersion and spontaneous plasmon emission spectra.
Fig. 4: Fermi-level-dependent emission spectra from graphene nanoribbon arrays.
Fig. 5: Enhancing radiation efficiency of bright hot plasmon emission with gold NDs on graphene.

Data availability

All measurement data are deposited in the Materials Cloud (, and other calculation data can be reproduced by the methods described in the Supplementary Information.


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This work was supported by US Department of Energy Office of Science grant no. DE-FG02-07ER46405. V.W.B. was supported by a Defense Advanced Research Projects Agency Young Faculty Award (grant no. YFA D18AP00043) and by the Gordon and Betty Moore Foundation through a Moore Inventors Fellowship. S.K. acknowledges support by a Samsung Scholarship. Parts of the text and results reported in this work have been reproduced from the thesis by L. Kim, at the California Institute of Technology, and are accessible at

Author information




L.K., V.W.B. and H.A.A. conceived the ideas. L.K. performed spectroscopy experiments, and performed inversion and gain calculations as well as emissivity calculations. L.K. and S.K. fabricated the sample and performed data analysis. P.K.J. contributed to the discussion of the ratio of stimulated to spontaneous emission rates calculations. All authors cowrote the paper. V.W.B. and H.A.A. supervised the project.

Corresponding authors

Correspondence to Victor W. Brar or Harry A. Atwater.

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The authors declare no competing interests.

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Peer review information Nature Materials thanks Ortwin Hess, Frank Koppens and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–16 and Discussion.

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Kim, L., Kim, S., Jha, P.K. et al. Mid-infrared radiative emission from bright hot plasmons in graphene. Nat. Mater. (2021).

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