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Photocarrier‐Induced Active Control of Second‐Order Optical Nonlinearity in Monolayer MoS 2
Author(s) -
Taghinejad Mohammad,
Xu Zihao,
Wang Hua,
Taghinejad Hossein,
Lee KyuTae,
Rodrigues Sean P.,
Adibi Ali,
Qian Xiaofeng,
Lian Tianquan,
Cai Wenshan
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201906347
Subject(s) - monolayer , materials science , ultrashort pulse , second harmonic generation , excited state , optoelectronics , modulation (music) , dielectric , electron , crystal (programming language) , optics , nanotechnology , laser , physics , atomic physics , quantum mechanics , computer science , acoustics , programming language
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 MoS 2 crystal can be substantially modulated up to ≈55% within a timeframe of ≈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 χ (2) and the density of photoexcited carriers in MoS 2 . Indeed, the depopulation of the conduction band electrons, at the vicinity of the high‐symmetry K/K′ points of MoS 2 , suppresses the contribution of interband electronic transitions in the effective χ (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.