期刊
SMALL
卷 16, 期 5, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/smll.201906347
关键词
2D materials; nonlinear optics; optical modulation; photoinduced effects; ultrafast optics
类别
资金
- National Science Foundation [ECCS-1609567, ECCS-1542174]
- Office of Naval Research [N00014-17-1-2555]
- U.S. Department of Energy, Office of Science, Solar Photochemistry Program [DE-FG02-12ER16347]
- Air Force Office of Scientific Research [FA9550-15-1-0342]
Atomically thin transition metal dichalcogenides (TMDs) in their excited states can serve as exceptionally small building blocks for active optical platforms. In this scheme, optical excitation provides a practical approach to control light-TMD interactions via the photocarrier generation, in an ultrafast manner. Here, it is demonstrated that via a controlled generation of photocarriers the second-harmonic generation (SHG) from a monolayer MoS2 crystal can be substantially modulated up to approximate to 55% within a timeframe of approximate to 250 fs, a set of performance characteristics that showcases the promise of low-dimensional materials for all-optical nonlinear data processing. The combined experimental and theoretical study suggests that the large SHG modulation stems from the correlation between the second-order dielectric susceptibility chi((2)) and the density of photoexcited carriers in MoS2. Indeed, the depopulation of the conduction band electrons, at the vicinity of the high-symmetry K/K ' points of MoS2, suppresses the contribution of interband electronic transitions in the effective chi((2)) of the monolayer crystal, enabling the all-optical modulation of the SHG signal. The strong dependence of the second-order optical response on the density of photocarriers reveals the promise of time-resolved nonlinear characterization as an alternative route to monitoring carrier dynamics in excited states of TMDs.
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