Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Room-temperature continuous-wave indirect-bandgap transition lasing in an ultra-thin WS2 disk


Small semiconductor lasers that can be integrated on a chip are essential for a wide range of optical applications, including optical computing, communication and sensing. Practical laser applications have only been developed with direct-bandgap materials because of a general belief that lasing action from indirect-bandgap materials is almost impossible. Here we report unexpected indirect-bandgap transition lasing in an ultra-thin WS2 disk. We demonstrate that a 50-nm-thick WS2 disk offers efficient optical gain and whispering gallery modes that are sufficient for lasing action. As a result, the WS2 disk exhibits indirect transition lasing, even under continuous-wave excitation at room temperature. Our experimental results are in close agreement with theoretical modelling for phonon-assisted photon lasing. The results derived from external cavity-free ultra-thin WS2 layers offer a new direction for van-der-Waals-material-based nanophotonics and introduce the possibility for optical devices based on indirect-bandgap materials.

This is a preview of subscription content, access via your institution

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Ultra-thin WS2 disk as a WGM cavity.
Fig. 2: Optically pumped WS2 disk.
Fig. 3: Characteristics of the lasing action.
Fig. 4: Coherence of the laser emission.

Data availability

All the relevant data that support the findings of this study are available from the corresponding authors on reasonable request.


  1. Ma, R.-M. & Oulton, R. F. Applications of nanolasers. Nat. Nanotechnol. 14, 12–22 (2019).

    Article  ADS  Google Scholar 

  2. Ning, C.-Z. Semiconductor nanolasers. Phys. Status Solidi B 247, 774–788 (2010).

    Article  ADS  Google Scholar 

  3. Pavesi, L. Will silicon be the photonic material of the third millenium? J. Phys. Condens. Matter 15, R1169 (2003).

    Article  ADS  Google Scholar 

  4. Canham, L. Gaining light from silicon. Nature 408, 411–412 (2000).

    Article  ADS  Google Scholar 

  5. Soref, R. Mid-infrared photonics in silicon and germanium. Nat. Photon. 4, 495–497 (2010).

    Article  ADS  Google Scholar 

  6. Liang, D. & Bowers, J. E. Recent progress in lasers on silicon. Nat. Photon. 4, 511–517 (2010).

    Article  ADS  Google Scholar 

  7. Rong, H. et al. An all-silicon Raman laser. Nature 433, 292–294 (2005).

    Article  ADS  Google Scholar 

  8. Rong, H. et al. A continuous-wave Raman silicon laser. Nature 433, 725–728 (2005).

    Article  ADS  Google Scholar 

  9. Takahashi, Y. et al. A micrometre-scale Raman silicon laser with a microwatt threshold. Nature 498, 470–474 (2013).

    Article  ADS  Google Scholar 

  10. Chen, M., Tsai, C. & Wu, M. Optical gain and co-stimulated emissions of photons and phonons in indirect bandgap semiconductors. Jpn J. Appl. Phys. 45, 6576 (2006).

    Article  ADS  Google Scholar 

  11. Tsai, C.-Y. Theoretical model for the optical gain coefficient of indirect-band-gap semiconductors. J. Appl. Phys. 99, 053506 (2006).

    Article  ADS  Google Scholar 

  12. Escalante, J. M. & Martínez, A. Theoretical study about the gain in indirect bandgap semiconductor optical cavities. Physica B 407, 2044–2049 (2012).

    Article  ADS  Google Scholar 

  13. Trupke, T., Green, M. A. & Würfel, P. Optical gain in materials with indirect transitions. J. Appl. Phys. 93, 9058–9061 (2003).

    Article  ADS  Google Scholar 

  14. Bao, S. et al. Low-threshold optically pumped lasing in highly strained germanium nanowires. Nat. Commun. 8, 1845 (2017).

    Article  ADS  Google Scholar 

  15. Pilon, F. A. et al. Lasing in strained germanium microbridges. Nat. Commun. 10, 2724 (2019).

    Article  ADS  Google Scholar 

  16. Camacho-Aguilera, R. E. et al. An electrically pumped germanium laser. Opt. Express 20, 11316–11320 (2012).

    Article  ADS  Google Scholar 

  17. Elbaz, A. et al. Ultra-low-threshold continuous-wave and pulsed lasing in tensile-strained GeSn alloys. Nat. Photon. 14, 375–382 (2020).

    Article  ADS  Google Scholar 

  18. Wirths, S. et al. Lasing in direct-bandgap GeSn alloy grown on Si. Nat. Photon. 9, 88–92 (2015).

    Article  ADS  Google Scholar 

  19. Pavesi, L., Dal Negro, L., Mazzoleni, C., Franzo, G. & Priolo, D. F. Optical gain in silicon nanocrystals. Nature 408, 440–444 (2000).

    Article  ADS  Google Scholar 

  20. Ye, Y. et al. Monolayer excitonic laser. Nat. Photon. 9, 733–737 (2015).

    Article  ADS  Google Scholar 

  21. Li, Y. et al. Room-temperature continuous-wave lasing from monolayer molybdenum ditelluride integrated with a silicon nanobeam cavity. Nat. Nanotechnol. 12, 987–992 (2017).

    Article  ADS  Google Scholar 

  22. Ge, X., Minkov, M., Fan, S., Li, X. & Zhou, W. Laterally confined photonic crystal surface emitting laser incorporating monolayer tungsten disulfide. npj 2D Mater. Appl. 3, 16 (2019).

    Article  Google Scholar 

  23. Reeves, L., Wang, Y. & Krauss, T. F. 2D material microcavity light emitters: to lase or not to lase? Adv. Opt. Mater. 6, 1800272 (2018).

    Article  Google Scholar 

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

    Article  ADS  Google Scholar 

  25. Liu, Y. et al. Room temperature nanocavity laser with interlayer excitons in 2D heterostructures. Sci. Adv. 5, eaav4506 (2019).

    Article  ADS  Google Scholar 

  26. Lohof, F. et al. Prospects and limitations of transition metal dichalcogenide laser gain materials. Nano Lett. 19, 210–217 (2018).

    Article  ADS  Google Scholar 

  27. Gutiérrez, H. R. et al. Extraordinary room-temperature photoluminescence in triangular WS2 monolayers. Nano Lett. 13, 3447–3454 (2013).

    Article  ADS  Google Scholar 

  28. Verre, R. et al. Transition metal dichalcogenide nanodisks as high-index dielectric Mie nanoresonators. Nat. Nanotechnol. 14, 679–683 (2019).

    Article  ADS  Google Scholar 

  29. Zhang, X. et al. Guiding of visible photons at the ångström thickness limit. Nat. Nanotechnol. 14, 844–850 (2019).

    Article  ADS  Google Scholar 

  30. van de Groep, J. et al. Exciton resonance tuning of an atomically thin lens. Nat. Photon 14, 426–430 (2020).

    Article  ADS  Google Scholar 

  31. Desai, S. B. et al. Strain-induced indirect to direct bandgap transition in multilayer WSe2. Nano Lett. 14, 4592–4597 (2014).

    Article  ADS  Google Scholar 

  32. Yuan, L., Wang, T., Zhu, T., Zhou, M. & Huang, L. Exciton dynamics, transport, and annihilation in atomically thin two-dimensional semiconductors. J. Phys. Chem. Lett. 8, 3371–3379 (2017).

    Article  Google Scholar 

  33. Burt, D. et al. Strain-relaxed GeSn-on-insulator (GeSnOI) microdisks. Opt. Express 29, 28959–28967 (2021).

    Article  ADS  Google Scholar 

  34. Wu, K. et al. All-optical phase shifter and switch near 1,550 nm using tungsten disulfide (WS2) deposited tapered fiber. Opt. Express 25, 17639–17649 (2017).

    Article  ADS  Google Scholar 

  35. Zhou, T. et al. Continuous-wave quantum dot photonic crystal lasers grown on on-axis Si (001). Nat. Commun. 11, 977 (2020).

    Article  ADS  Google Scholar 

  36. Frost, T., Banerjee, A., Sun, K., Chuang, S. L. & Bhattacharya, P. InGaN/GaN quantum dot red (λ = 630 nm) laser. IEEE J. Quantum Electron. 49, 923–931 (2013).

    Article  ADS  Google Scholar 

  37. Hayenga, W. E. et al. Second-order coherence properties of metallic nanolasers. Optica 3, 1187–1193 (2016).

    Article  ADS  Google Scholar 

  38. Liu, H., Wang, T., Wang, C., Liu, D. & Luo, J. Exciton radiative recombination dynamics and nonradiative energy transfer in two-dimensional transition-metal dichalcogenides. J. Phys. Chem. C 123, 10087–10093 (2019).

    Article  Google Scholar 

  39. Mylnikov, V. et al. Lasing action in single subwavelength particles supporting supercavity modes. ACS Nano 14, 7338–7346 (2020).

    Article  Google Scholar 

  40. Berkdemir, A. et al. Identification of individual and few layers of WS2 using Raman spectroscopy. Sci. Rep. 3, 1755 (2013).

    Article  Google Scholar 

Download references


This work was supported by the National Research Foundation of Korea (NRF-2019R1A2C2003313) and the National R&D Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2020M3H3A1105796, 2021M3F3A2A03017083). We acknowledge support provided by the Samsung Science and Technology Foundation (SSTF-BA1902-03) and a Korea University Grant. Y.D.K. acknowledges support from the NRF of Korea (2021K1A3A1A32084700, 2021R1A2C2093155). Electron-beam lithography systems were investigated in the Multidimensional Materials Research Center at Kyung Hee University (2021R1A6C101A437).

Author information

Authors and Affiliations



S.-H.G. conceptualized and supervised the study. J.S. and S.-H.G. performed all data analysis and visualization. J.S., S.P. and Y.D.K. fabricated the sample structures. J.S., J.S.M., D.S. and S.W.L. conducted the optical experiments and data collection. S.-H.G., J.S. and H.C. developed the theoretical model. S.-H.G. and J.S. wrote the original draft. S.-H.G., J.-H.K. and Y.D.K. reviewed and edited the final manuscript.

Corresponding author

Correspondence to Su-Hyun Gong.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Photonics thanks Di Liang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

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

Supplementary information

Supplementary Information

Supplementary Figs. 1–14 and Table 1.

Rights and permissions

Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Sung, J., Shin, D., Cho, H. et al. Room-temperature continuous-wave indirect-bandgap transition lasing in an ultra-thin WS2 disk. Nat. Photon. 16, 792–797 (2022).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing