期刊
NANO LETTERS
卷 18, 期 3, 页码 1686-1692出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.7b04707
关键词
Plasmonic hot carrier injection; bilayer transitional metal dichalcogenides; inversion symmetry; charge induced second harmonic generation; transient absorption spectroscopy
类别
资金
- Singapore National Research Foundation through the NRF Investigatorship Award [NRF-NRFI2015-03]
- Singapore Ministry of Education via AcRF Tier 2 grant [MOE2015-T2-1-047, MOE2017-T2-1-040]
- Singapore Ministry of Education via AcRF Tier 1 grant [RG 113/16]
Modulating second harmonic generation (SHG) by a static electric field through either electric-field-induced SHG or charge-induced SHG has been well documented. Nonetheless, it is essential to develop the ability to dynamically control and manipulate the nonlinear properties, preferably at high speed. Plasmonic hot carriers can be resonantly excited in metal nanoparticles and then injected into semiconductors within 10-100 fs, where they eventually decay on a comparable time scale. This allows one to rapidly manipulate all kinds of characteristics of semiconductors, including their nonlinear properties. Here we demonstrate that plasmonically generated hot electrons can be injected from plasmonic nanostructure into bilayer (2L) tungsten diselenide (WSe2), breaking the material inversion symmetry and thus inducing an SHG. With a set of pump-probe experiments we confirm that it is the dynamic separation electric field resulting from the hot carrier injection (rather than a simple optical field enhancement) that is the cause of SHG. Transient absorption measurement further substantiate the plasmonic hot electrons injection and allow us to measure a rise time of similar to 120 fs and a fall time of 1.9 ps. Our study creates opportunity for the ultrafast all-optical control of SHG in an all-optical manner that may enable a variety of applications.
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