Ultra-strong nonlinear optical processes and trigonal warping in MoS2 layers
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Saynatjoki, A., Karvonen, L., Rostami, H., Autere, A., Mehravar, S., Lombardo, A., Norwood, R., et al. (2017). Ultra-strong nonlinear optical processes and trigonal warping in MoS2 layers. Nature Communications, 8 (836)https://doi.org/10.1038/s41467-017-00749-4
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.
We acknowledge funding from the Academy of Finland (Nos: 276376, 284548, 295777, 298297, and 304666), TEKES (NP-Nano, OPEC), Royal Academy of Engineering (RAEng) Research Fellowships, Fondazione Istituto Italiano di Tecnologia, the Graphene Flagship, ERC grants Hetero2D, Nokia Foundation, EPSRC Grants EP/K01711X/1, EP/K017144/1, EP/L016087/1, AFOSR COMAS MURI (FA9550-10-1-0558), ONR NECom MURI, CIAN NSF ERC under Grant EEC-0812072, and TRIF Photonics funding from the state of Arizona and the Micronova, Nanofabrication Centre of Aalto University.
EC FP7 ERC (319277)
EC FP7 FET FLAGSHIP (604391)
European Commission Horizon 2020 (H2020) Future and Emerging Technologies (FET) (696656)
Royal Society (wm090070)
External DOI: https://doi.org/10.1038/s41467-017-00749-4
This record's URL: https://www.repository.cam.ac.uk/handle/1810/265660
Attribution 4.0 International
Licence URL: http://creativecommons.org/licenses/by/4.0/