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Electrically Tunable Nonequilibrium Optical Response of Graphene
Eva A A Pogna1,2, Andrea Tomadin3, Osman Balci4
1NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, 56127 Pisa, Italy.
ACS Nano
|February 21, 2022
Summary
Electrostatic gating tunes single layer graphene's optical response. This tunability allows control over photobleaching relaxation and photoinduced absorption, making graphene ideal for tunable optical devices.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Optoelectronics
Background:
- Electrostatic gating is vital for tuning material optical responses in optoelectronics.
- Single layer graphene (SLG) possesses a unique band structure enabling Fermi energy control and tunable optical absorption.
Purpose of the Study:
- To investigate the tunability of single layer graphene's (SLG) nonequilibrium optical response in the near-infrared spectrum.
- To explore the effects of electrostatic gating on SLG's photobleaching relaxation dynamics and photoinduced absorption.
Main Methods:
- Ionic liquid gating was employed to tune the Fermi energy (E_F) of SLG across a range from -650 to 250 meV.
- Optical response measurements were conducted in the near-infrared region (1000-1700 nm).
Main Results:
- Photobleaching relaxation dynamics slowed down as E_F increased towards the Pauli blocking threshold.
- For E_F exceeding the Pauli blocking threshold, photobleaching transitioned to photoinduced absorption due to hot electron excitation.
- Optical phonon emission quenching was identified as the cause for slowed relaxation dynamics.
Conclusions:
- Electrostatic gating effectively controls the nonequilibrium optical response of SLG.
- The ability to tune both recovery time and the sign of the optical response makes SLG a promising material for advanced tunable saturable absorbers.
