Ultra-strong nonlinear optical processes and trigonal warping in MoS2 layers

Research output: Contribution to journalArticleScientificpeer-review


Original languageEnglish
Article number893
JournalNature Communications
Issue number1
Publication statusPublished - 1 Dec 2017
MoE publication typeA1 Journal article-refereed


  • Antti Säynätjoki
  • Lasse Karvonen
  • Habib Rostami
  • Anton Autere
  • Soroush Mehravar
  • Antonio Lombardo
  • Robert A. Norwood
  • Tawfique Hasan
  • Nasser Peyghambarian
  • Harri Lipsanen

  • Khanh Kieu
  • Andrea C. Ferrari
  • Marco Polini
  • Zhipei Sun

Research units

  • University of Eastern Finland
  • Italian Institute of Technology
  • University of Arizona
  • University of Cambridge


Nonlinear optical processes, such as harmonic generation, are of great interest for various applications, e.g., microscopy, therapy, and frequency conversion. However, high-order harmonic conversion is typically much less efficient than low-order, due to the weak intrinsic response of the higher-order nonlinear processes. Here we report ultra-strong optical nonlinearities in monolayer MoS2 (1L-MoS2): the third harmonic is 30 times stronger than the second, and the fourth is comparable to the second. The third harmonic generation efficiency for 1L-MoS2 is approximately three times higher than that for graphene, which was reported to have a large χ (3). We explain this by calculating the nonlinear response functions of 1L-MoS2 with a continuum-model Hamiltonian and quantum mechanical diagrammatic perturbation theory, highlighting the role of trigonal warping. A similar effect is expected in all other transition-metal dichalcogenides. Our results pave the way for efficient harmonic generation based on layered materials for applications such as microscopy and imaging.

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