Dual Resonant Sum Frequency Generations from Two-Dimensional Materials.
basic_science · Level V
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- Record sourced from PubMed, PMID 32422047.
- Also identified by DOI 10.1021/acs.nanolett.0c01363.
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Abstract
We propose dual resonant optical sum frequency generation (SFG), where the two most singular resonances could be selected, and report for the monolayer (1L-) WSe<sub>2</sub> when one (ω<sub>1</sub>) of two excitation pulses is resonant to A exciton and their sum frequency (ω<sub>1</sub> + ω<sub>2</sub>) to D exciton. The dual resonant SFG confirms that, under an irradiation of ω<sub>1</sub> and ω<sub>2</sub> pulses with the same fluence of ∼1.4 × 10<sup>10</sup> W/m<sup>2</sup>, its signal intensity could be enhanced about 20 times higher than the resonant SHG (i.e., 2ω<sub>1</sub> to the D excitonic absorption). Further, the dual resonant SFG intensity of 1L-WSe<sub>2</sub> is found to be 1 order of magnitude higher than the single resonant SFG intensity of 1L-WS<sub>2</sub> under the same condition of two-pulse irradiation. Finally, observations of the dual resonant SFG are thoroughly examined using real-time time-dependent density functional theory (rt-TDDFT), and the relevant nonlinear optical characteristics are scrutinized using the Greenwood-Kubo formalism.