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Multiphonon-assisted lasing beyond the fluorescence spectrum


Lasing typically starts from fluorescence, and the laser wavelength is therefore limited to the fluorescence spectrum of the gain material. Accessing wavelengths beyond this intrinsic emission spectrum requires emission assisted by multiphonon processes. However, this is much weaker than the fluorescence originating from direct transitions between electronic energy levels, which only involve a small number of phonons. Here, we present the realization of lasers far beyond the fluorescence spectrum in Yb-doped YCa4O(BO3)3 crystals. We selectively amplify three- to eight-phonon processes and suppress all the fewer-phonon ones, which we attribute to constructive interactions of vibrational modes from free oxygen sites. We obtain an overall spectral tuneability of 1,110–1,465 nm in five segments, each with its own configuration, corresponding to the three- to seven-phonon cases. The longest (eight-phonon) lasing wavelength can reach 1,518 nm, over 400 nm beyond the fluorescence spectrum. Our results shed light on strengthening the original weak electron–phonon–photon interaction and give rise to a search for on-demand lasers operating outside the fluorescence spectrum.

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Fig. 1: Schematic diagram of the multiphonon–electron coupled laser.
Fig. 2: Yb:YCOB crystal and laser generation.
Fig. 3: Lasing beyond the fluorescence spectrum.
Fig. 4: Mechanism of multiphonon–electron coupled lasing.

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Source data are available for this paper. All other data that support the findings of this study are available from the corresponding author upon reasonable request. Source data are provided with this paper.


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This work was supported by the National Key Research and Development Program of China (grant nos. 2021YFB3601504 and 2021YFA0717800) and the Natural Science Foundation of China (grant nos. 52025021, 92163207, 51890863 and 52002220). F.L. acknowledges the support of Future Plans of Young Scholars at Shandong University. F.L. acknowledges H. Si and Y. Cheng for support with laser measurements. F.L. acknowledges W. Liu, J. Feng, and G. Zhang for crystal growth of Yb:La2CaB10O19, Gd:Na3La9O3(BO3)8, Li3K9Gd3(BO3)7 and Rb7SrGd2(B5O12)3.

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Authors and Affiliations



H.Y. and H.Z. conceived and supervised the project. F.L., C.H. and D.L. performed the laser experiments and wrote the manuscript. Q.F. performed some laser experiments. Y.F. performed some spectral measurements. Y.-F.C. provided helpful suggestions and theoretical analysis on the electron–phonon coupling effect. All authors contributed to the discussion and the preparation of the manuscript.

Corresponding authors

Correspondence to Haohai Yu, Huaijin Zhang or Yan-Feng Chen.

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Nature Physics thanks Anton Husakou and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–27, discussion and Tables 1–5.

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Source data

Source Data Fig. 3

Laser wavelength and laser power.

Source Data Fig. 4

Raman spectrum and phonon dispersion.

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Liang, F., He, C., Lu, D. et al. Multiphonon-assisted lasing beyond the fluorescence spectrum. Nat. Phys. 18, 1312–1316 (2022).

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