Electrically Tunable Nonequilibrium Optical Response of Graphene.
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Authors
Pogna, Eva AA
Tomadin, Andrea
Paradisanos, Ioannis
Guizzardi, Michele
Pedrinazzi, Paolo
Mignuzzi, Sandro
Polini, Marco
Publication Date
2022-03-22Journal Title
ACS Nano
ISSN
1936-0851
Publisher
American Chemical Society (ACS)
Type
Article
This Version
AM
Metadata
Show full item recordCitation
Pogna, E. A., Tomadin, A., Balci, O., Soavi, G., Paradisanos, I., Guizzardi, M., Pedrinazzi, P., et al. (2022). Electrically Tunable Nonequilibrium Optical Response of Graphene.. ACS Nano https://doi.org/10.1021/acsnano.1c04937
Abstract
The ability to tune the optical response of a material via electrostatic gating is crucial for optoelectronic applications, such as electro-optic modulators, saturable absorbers, optical limiters, photodetectors, and transparent electrodes. The band structure of single layer graphene (SLG), with zero-gap, linearly dispersive conduction and valence bands, enables an easy control of the Fermi energy, EF, and of the threshold for interband optical absorption. Here, we report the tunability of the SLG nonequilibrium optical response in the near-infrared (1000-1700 nm/0.729-1.240 eV), exploring a range of EF from -650 to 250 meV by ionic liquid gating. As EF increases from the Dirac point to the threshold for Pauli blocking of interband absorption, we observe a slow-down of the photobleaching relaxation dynamics, which we attribute to the quenching of optical phonon emission from photoexcited charge carriers. For EF exceeding the Pauli blocking threshold, photobleaching eventually turns into photoinduced absorption, because the hot electrons' excitation increases the SLG absorption. The ability to control both recovery time and sign of the nonequilibrium optical response by electrostatic gating makes SLG ideal for tunable saturable absorbers with controlled dynamics.
Keywords
cooling dynamics, graphene, hot electrons, optical phonons, phonon bottleneck, tunable dynamics
Sponsorship
Engineering and Physical Sciences Research Council (EP/K01711X/1)
Engineering and Physical Sciences Research Council (EP/K017144/1)
Engineering and Physical Sciences Research Council (EP/L016087/1)
European Research Council (319277)
European Research Council (842251)
Identifiers
External DOI: https://doi.org/10.1021/acsnano.1c04937
This record's URL: https://www.repository.cam.ac.uk/handle/1810/332462
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