Terahertz phase jumps for ultra-sensitive graphene plasmon sensing

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Surface Plasmon Resonance (SPR) is a phenomenon sensitive to changes in the refractive index near a metal surface.
• Graphene, a single layer of carbon atoms, exhibits unique electronic properties, including tunable surface conductivity.
• Terahertz (THz) radiation offers non-ionizing and label-free detection capabilities, but its application in sensing is often limited by sensitivity.

Purpose of the Study:

• To investigate the phase behavior of terahertz radiation under SPR conditions supported by doped graphene.
• To explore the potential of graphene-based SPR for ultra-sensitive label-free detection of biomolecules.
• To evaluate the performance of THz-SPR phase sensing compared to traditional THz-amplitude-based methods.

Main Methods:

• Theoretical analysis and simulation verifications of reflected THz radiation phase behavior.
• Investigation of the dependence of phase on the angle of incidence for TM-polarized waves.
• Analysis of the transition from step-like to Fano lineshape in resonance phase dependence.

Main Results:

• Observed abrupt jump-like changes in the phase dependence on the angle of incidence.
• Demonstrated a transformation from step-like to Fano lineshape in resonance phase dependence under optimal SPR conditions.
• Achieved a high figure of merit (FOM) of up to 171 for refractive index sensing based on THz phase information.
• Showcased tunable sensing range by adjusting graphene's surface conductivity via doping or layer number.

Conclusions:

• Graphene-supported SPR in the terahertz regime exhibits unique phase behavior with potential for ultra-sensitive sensing.
• The phase jump characteristic offers a valuable readout for refractive index sensing, outperforming traditional THz-ATR spectroscopy.
• Graphene plasmon's THz phase response is promising for tunable, ultra-sensitive (bio)chemical sensing applications.