Photocarrier‐Induced Active Control of Second‐Order Optical Nonlinearity in Monolayer MoS ₂

Journal Article · 13 January 2020 · Small

DOI: https://doi.org/10.1002/smll.201906347 · OSTI ID:1582685

Taghinejad, Mohammad ^[1]; Xu, Zihao ^[2]; Wang, Hua ^[3]; Taghinejad, Hossein ^[1]; Lee, Kyu‐Tae ^[1]; Rodrigues, Sean P. ^[4]; Adibi, Ali ^[1]; Qian, Xiaofeng ^[3]; Lian, Tianquan ^[2]; Cai, Wenshan  ^[5]

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1. School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332‐0250 USA
2. Department of Chemistry Emory University Atlanta GA 30322 USA
3. Department of Materials Science and Engineering Texas A&,M University College Station TX 77843 USA
4. School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332‐0250 USA, Toyota Research Institute of North America Ann Arbor MI 48105 USA
5. School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332‐0250 USA, School of Materials Science and Engineering Georgia Institute of Technology Atlanta GA 30332 USA

Abstract 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.

• Sponsoring Organization: USDOE
• OSTI ID: 1582685
• Journal Information: Small, Journal Name: Small Journal Issue: 5 Vol. 16; ISSN 1613-6810
• Publisher: Wiley Blackwell (John Wiley & Sons)Copyright Statement
• Country of Publication: Germany
• Language: English