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Interlayer exciton laser of extended spatial coherence in atomically thin heterostructures


Two-dimensional semiconductors have emerged as a new class of materials for nanophotonics owing to their strong exciton–photon interaction1,2 and their ability to be engineered and integrated into devices3. Here we take advantage of these properties to engineer an efficient lasing medium based on direct-bandgap interlayer excitons in rotationally aligned atomically thin heterostructures4. Lasing is measured from a transition-metal dichalcogenide heterobilayer (WSe2–MoSe2) integrated in a silicon nitride grating resonator. An abrupt increase in the spatial coherence of the emission is observed across the lasing threshold. The work establishes interlayer excitons in two-dimensional heterostructures as a gain medium with spatially coherent lasing emission and potential for heterogeneous integration. With electrically tunable exciton–photon interaction strengths5 and long-range dipolar interactions, these interlayer excitons are promising for application as low-power, ultrafast lasers and modulators and for the study of many-body quantum phenomena6.

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Fig. 1: Illustration of the heterobilayer/grating-cavity laser system.
Fig. 2: Properties of the heterobilayer and grating cavity.
Fig. 3: Spectral properties of the interlayer exciton laser.
Fig. 4: First-order coherence of the interlayer exciton laser.

Data availability

Data that support the findings of this study are available from the corresponding author on reasonable request.


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We acknowledge support from the Army Research Office under awards W911NF-17-1-0312. H.D. acknowledges support from the Asian Office of Aerospace R&D under awards FA2386-18-1-4086. E.T. acknowledges support from Intel Corp., and the Welch Foundation grant F-2018-20190330.

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Authors and Affiliations



E.Y.P. performed the measurements of the indirect exciton laser. L.Z. designed, fabricated and characterized the grating cavity. L.Z. exfoliated and characterized the WSe2 and MoSe2 monolayers with help from E.Y.P. G.W.B. made the rotationally aligned structure. R.G., E.Y.P. and L.Z. performed simulations of the device. H.D. and E.T. supervised the project. E.Y.P., L.Z. and H.D. performed data analysis and wrote the manuscript with input from all authors.

Corresponding author

Correspondence to Hui Deng.

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Extended data figures and tables

Extended Data Fig. 1 Heterobilayer twist angle.

a, b, Optical image (a) and angle-resolved SHG measurements (b; open circles) of WSe2/MoSe2 heterobilayers. c, d, As a, b but for a different sample. The field of view of the optical images is around 60 μm. Solid lines in b, d, are fits by a cos2(3θ) function, which give relative twist angles of 0.22°± 1.78° for b, and 0.34° ± 1.5° for d.

Extended Data Fig. 2 Interlayer exciton lifetime.

a, Time-resolved PL spectrum for TM emission. b, Line-cut of a near 1.38 eV. Red line is a bi-exponential fit to the data, with a fitted lifetime of 2 ns.

Extended Data Fig. 3 Spatial mapping of PL.

The normalized intensity of PL from the device is shown as a function of position. Spectral filters centred around their respective exciton peak energies were applied for each image. The white contours mark the regions of heterobilayer (a), MoSe2 (b) and WSe2 (c).

Extended Data Fig. 4 Electric field profiles.

Shown are simulated normalized electric field profiles as a function of position near the centre of a grating cavity with lateral dimensions of 100 μm × 100 μm. a, TE-polarized light at the cavity resonance at k = 0, showing strong field enhancement in the grating layer including at its surface where the heterobilayer is placed. b, TM-polarized light at the same wavelength as a, showing negligible cavity effects. White lines outline different layers of the grating cavity. The corresponding enhancement of the exciton radiative decay rate, or the Purcell factor, is calculated to be around 2.4.

Extended Data Fig. 5 Power-dependence reproducibility.

The photon occupancy (red) and linewidth (blue) of TE emission from the heterobilayer versus input pump power, similar to that shown in Fig. 3b of the main text but measured on a different day to show the reproducibility of the device. The error bars on the photon occupancy data include the shot noise and detector read noise. The error bars on the linewidth data correspond to the 95% confidence interval of the Lorentzian fit.

Extended Data Fig. 6 Rate equation fitting.

The log–log plot of photon occupancy versus pump power. The diamonds represent measured data shown in Fig. 3b of the main text, and the solid line is a rate-equation fitting. Details of the rate equation simulation are described in Methods.

Extended Data Fig. 7 Temperature dependence.

Temperature-dependent real space PL spectra of the sample studied in the main text.

Extended Data Fig. 8 Experimental setup.

Schematic diagram of the optical experimental setup as described in Methods. BS, beam splitter; LP, long-pass filter; BP, band-pass filter; CCD, charge-coupled device.

Extended Data Fig. 9 Temporal coherence.

Shown are temporal coherence interference fringes at g(1)(τ = 0) measured using a two-retro-reflector Michelson interferometer under CW excitation above threshold. a, Interferogram image at τ = 0. b, Horizontal line-cut of a around y = 1.5 μm. The red line is a fit to the Gaussian pump beam profile modulated by a cosine function. Here g(1)(τ = 0) = 0.78.

Extended Data Table 1 Rate equation fitting parameters

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Paik, E.Y., Zhang, L., Burg, G.W. et al. Interlayer exciton laser of extended spatial coherence in atomically thin heterostructures. Nature 576, 80–84 (2019).

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