Nonlinear THz conductivity dynamics in P-type CVD-grown graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Optics and Photonics

Background:

• Graphene's unique electronic properties make it a promising material for optoelectronic applications.
• Terahertz (THz) radiation interacts strongly with graphene, offering opportunities for novel device functionalities.
• Understanding nonlinear optical responses in graphene is crucial for high-power THz applications.

Purpose of the Study:

• To investigate the THz-induced transparency effect in chemical vapor deposition (CVD)-grown graphene.
• To elucidate the underlying physical mechanisms responsible for the observed nonlinear optical behavior.
• To determine the temporal dynamics of the induced transparency phenomenon.

Main Methods:

• Fabrication of high-quality graphene using chemical vapor deposition (CVD).
• Utilized time-resolved terahertz (THz) pump/THz probe spectroscopy.
• Measured transmission spectra across a range of THz field strengths.

Main Results:

• Observed strong THz-induced transparency, with peak-field transmission reaching 92-96%, significantly higher than the 74% at lower field strengths.
• Demonstrated that the induced transparency recovers within 2-3 picoseconds (ps).
• Correlated the transparency effect with suppressed carrier mobility and conductivity due to nonlinear carrier pumping.

Conclusions:

• CVD-grown graphene exhibits significant nonlinear optical response under strong THz fields, leading to induced transparency.
• The observed phenomenon is attributed to nonlinear pumping of carriers, which alters graphene's conductivity.
• The rapid recovery time suggests potential for ultrafast THz modulation applications using graphene.