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Size and edge dependence of two-photon absorption in rectangular graphene quantum dots
Optics Express
|April 4, 2018
Summary
This study explores two-photon absorption in graphene quantum dots (GQDs). GQD properties, like semiconductor or metallic behavior, depend on edge size, influencing TPA tuning.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Optics
Background:
- Graphene quantum dots (GQDs) exhibit unique electronic and optical properties.
- Two-photon absorption (TPA) is a crucial nonlinear optical phenomenon with applications in various fields.
- Understanding TPA in GQDs requires theoretical investigation of size and edge effects.
Purpose of the Study:
- To theoretically investigate the size and edge-dependence of TPA in rectangular GQDs.
- To derive the TPA cross-section and transition selection rules around the K point.
- To analyze the impact of zigzag and armchair edge dimensions on TPA.
Main Methods:
- Theoretical investigation using the Dirac equation under hard wall boundary conditions.
- Derivation of the TPA cross-section for interband transitions.
- Analysis of transition selection rules based on GQD dimensions.
Main Results:
- Rectangular GQDs behave as semiconductors for zigzag-edge sizes M = 3M0 ± 1 and metallic for M = 3M0.
- For semiconducting GQDs, TPA is tunable by both edge sizes, with armchair-edge contributing more.
- For metallic GQDs, armchair-edge size dictates absorption peak position and TPA coefficient magnitude, with resonant enhancement.
Conclusions:
- Graphene quantum dot electronic and optical properties are highly sensitive to edge structure and dimensions.
- Tailoring GQD dimensions allows for controlled tuning of two-photon absorption characteristics.
- The findings provide insights for designing GQD-based optical devices.
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