Gate-Tunable Optical Nonlinearities and Extinction in Graphene/LaAlO<sub>3</sub>/SrTiO<sub>3</sub> Nanostructures.
basic_science · Level V
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- Record sourced from PubMed, PMID 32870015.
- Also identified by DOI 10.1021/acs.nanolett.0c01379.
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Abstract
We explore the ultrafast optical response of graphene subjected to intense (∼10<sup>6</sup> V/cm) local (∼10 nm) electric fields. Nanoscale gating of graphene is achieved using a voltage-biased, SrTiO<sub>3</sub>-based conductive nanowire junction "written" directly under the graphene and isolated from it by an insulating ultrathin (<2 nm) LaAlO<sub>3</sub> barrier. Upon illumination with ultrafast visible-to-near-infrared (VIS-NIR) light pulses, the local field from the nanojunction creates a strong gate-tunable second-order nonlinearity in the graphene and produces a substantial difference-frequency (DFG) and sum-frequency generation (SFG) response detected by the nanojunction. Spectrally sharp, gate-tunable extinction features (>99.9%) are observed in the VIS-NIR and SFG spectral ranges, in parameter regimes that are positively correlated with the enhanced nonlinear response. The observed graphene-light interaction and nonlinear response are of fundamental interest and open the way for future exploitation in graphene-based optical devices such as phase shifters, modulators, and nanoscale THz sources.