Intrinsic restoring enabled mode-selective frequency shifts in self-referenced humidity sensing

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Plasmon-induced transparency (PIT) enhances light-matter interactions but dynamic tuning typically shows uniform frequency shifts with graphene carrier mobility.
• Existing PIT systems lack precise control over individual spectral feature shifts.

Purpose of the Study:

• To propose and investigate a novel periodic array of Π-shaped graphene and graphene strips for achieving triple PIT.
• To explore the dynamic tuning mechanism of the proposed structure with varying graphene carrier mobility.
• To demonstrate the potential application of the triple PIT mechanism in optical humidity sensing.

Main Methods:

• Numerical simulations of a periodic array comprising Π-shaped graphene and graphene strips.
• Analysis of plasmon resonance coupling and destructive interference between bright and dark modes.
• Investigation of transmission spectra and frequency shifts of transmission dips as a function of graphene carrier mobility.

Main Results:

• Achieved triple PIT through a composite mechanism involving destructive interference and bright mode coupling.
• Observed selective frequency shifts in four distinct transmission dips with increasing carrier mobility.
• Demonstrated stability of the first transmission dip (dip1) due to dominant dark mode influence, counteracting typical red-shifts.
• Proposed a self-referencing optical humidity sensor with a sensitivity of 0.49 GHz/%RH.

Conclusions:

• The proposed composite mechanism enables precise control over PIT spectral features.
• The stable dip1 offers a robust reference point for sensing applications.
• The developed triple PIT structure shows significant potential for high-performance optical sensing, particularly for humidity detection.