Ultrafast Graphene-Plasmonic Hybrid Metasurface Saturable Absorber with Low Saturation Fluence

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• Emerging materials with enhanced optical nonlinearities are crucial for advanced optical systems.
• Nonlinear metamaterials and metasurfaces offer solutions to limitations of natural nonlinear materials.

Purpose of the Study:

• To design a hybrid graphene-plasmonic metasurface for enhanced saturable absorption at low power.
• To investigate the effect of nonequilibrium carriers in nanoscale hotspots on graphene's saturable absorption.

Main Methods:

• Theoretical design and experimental fabrication of subwavelength-thick hybrid graphene-plasmonic metasurfaces.
• Utilizing pump-probe measurements to assess saturable absorption enhancement and recovery time.
• Autocorrelation measurements to observe pulse narrowing effects.

Main Results:

• Achieved over 3 orders of magnitude reduction in saturation fluence (from ~1 mJ/cm² to ~100 nJ/cm²).
• Demonstrated ultrashort saturable absorption recovery time (<60 fs).
• Observed pulse narrowing, indicating potential for ultrafast optical signal processing.

Conclusions:

• Hybrid graphene-plasmonic metasurfaces offer a promising platform for ultrafast, low-saturation fluence optical devices.
• The design can be tailored for various infrared spectral regions.
• Enables development of compact, low-threshold mode-locked lasers and high-speed optical information processing.