Multiphoton absorption enhancement by graphene-gold nanostructure.

Area of Science:

• Nanophotonics
• Molecular Spectroscopy
• Materials Science

Background:

• Multiphoton absorption is crucial for various spectroscopic techniques.
• Existing methods for enhancing these signals often lack tunability.
• Graphene and gold nanostructures offer unique optical properties.

Purpose of the Study:

• To design and demonstrate a hybrid graphene-gold nanoantenna for enhanced multiphoton absorption.
• To achieve tunable enhancement of N-photon absorption signals in molecules.
• To explore highly nonlinear light-matter interactions.

Main Methods:

• Fabrication of a hybrid nanoantenna combining graphene and gold nanorods.
• Utilizing gate voltage to tune graphene resonances for specific absorption orders.
• Optimizing gold nanorod geometry for enhanced fluorescence emission.
• Spectroscopic characterization and theoretical prediction of signal enhancement.

Main Results:

• Demonstrated tunable molecular absorption in mid-infrared and terahertz bands using graphene.
• Achieved significant enhancement of fluorescence signal for ATTO 700 dye.
• Predicted enhancement factors exceeding 5 orders of magnitude for two-photon absorption.
• Predicted enhancement factors exceeding 13 orders of magnitude for higher-order N-photon absorption.

Conclusions:

• The hybrid graphene-gold nanoantenna is a promising platform for enhancing nonlinear light-matter interactions.
• Tunable control over spectral resonances and absorption orders is achievable.
• This technology has potential applications in sensitive molecular detection and spectroscopy.